// file      : libbuild2/dist/operation.cxx -*- C++ -*-
// license   : MIT; see accompanying LICENSE file

#include <libbuild2/dist/operation.hxx>

#include <libbutl/sha1.hxx>
#include <libbutl/sha256.hxx>

#include <libbutl/filesystem.hxx> // try_mkdir_p(), cpfile()

#include <libbuild2/file.hxx>
#include <libbuild2/dump.hxx>
#include <libbuild2/scope.hxx>
#include <libbuild2/target.hxx>
#include <libbuild2/context.hxx>
#include <libbuild2/algorithm.hxx>
#include <libbuild2/filesystem.hxx>
#include <libbuild2/diagnostics.hxx>

#include <libbuild2/dist/types.hxx>
#include <libbuild2/dist/rule.hxx>
#include <libbuild2/dist/module.hxx>

using namespace std;
using namespace butl;

namespace build2
{
  namespace dist
  {
    // install -d <dir>
    //
    static void
    install (const process_path*, context&, const dir_path&);

    // install <file> <dir>[/<name>]
    //
    // Return the destination file path.
    //
    static path
    install (const process_path*, const file&, const dir_path&, const path&);

    // tar|zip ... <dir>/<pkg>.<ext> <pkg>
    //
    // Return the archive file path.
    //
    static path
    archive (context& ctx,
             const dir_path& root,
             const string& pkg,
             const dir_path& dir,
             const string& ext);

    // <ext>sum <arc> > <dir>/<arc>.<ext>
    //
    // Return the checksum file path.
    //
    static path
    checksum (context&,
              const path& arc, const dir_path& dir, const string& ext);

    static operation_id
    dist_operation_pre (context&, const values&, operation_id o)
    {
      if (o != default_id)
        fail << "explicit operation specified for dist meta-operation";

      return o;
    }

    static void
    dist_load_load (const values& vs,
                    scope& rs,
                    const path& bf,
                    const dir_path& out_base,
                    const dir_path& src_base,
                    const location& l)
    {
      // @@ TMP: redo after release (do it here and not in execute, also add
      //         custom search and do the other half there).
      //
#if 0
      if (rs.out_path () != out_base || rs.src_path () != src_base)
        fail (l) << "dist meta-operation target must be project root directory";
#endif

      // Mark this project as being distributed.
      //
      if (auto* m = rs.find_module<module> (module::name))
        m->distributed = true;

      perform_load (vs, rs, bf, out_base, src_base, l);
    }

    // Enter the specified source file as a target of type T. The path is
    // expected to be normalized and relative to src_root. If the third
    // argument is false, then first check if the file exists. If the fourth
    // argument is true, then set the target's path.
    //
    template <typename T>
    static const T*
    add_target (const scope& rs, const path& f, bool e = false, bool s = false)
    {
      tracer trace ("dist::add_target");

      path p (rs.src_path () / f);
      if (e || exists (p))
      {
        dir_path d (p.directory ());

        // Figure out if we need out.
        //
        dir_path out (!rs.out_eq_src () ? out_src (d, rs) : dir_path ());

        const T& t (rs.ctx.targets.insert<T> (
                      move (d),
                      move (out),
                      p.leaf ().base ().string (),
                      p.extension (),              // Specified.
                      trace));

        if (s)
          t.path (move (p));

        return &t;
      }

      return nullptr;
    }

    // Recursively traverse an src_root subdirectory entering/collecting the
    // contained files and file symlinks as the file targets and skipping
    // entries that start with a dot. Follow directory symlinks (preserving
    // their names) and fail on dangling symlinks. Also detect directory
    // symlink cycles.
    //
    struct subdir
    {
      const subdir* prev;
      const dir_path& dir;
    };

    static void
    add_subdir (const scope& rs,
                const dir_path& sd,
                action_targets& files,
                const subdir* prev = nullptr)
    {
      dir_path d (rs.src_path () / sd);

      const subdir next {prev, d};

      try
      {
        for (const dir_entry& e: dir_iterator (d, dir_iterator::no_follow))
        {
          const path& n (e.path ());

          if (!n.empty () && n.string ().front () != '.')
          try
          {
            if (e.type () == entry_type::directory) // Can throw.
            {
              // If this is a symlink, check that it doesn't cause a cycle.
              //
              if (e.ltype () == entry_type::symlink)
              {
                // Note that the resulting path will be absolute and
                // normalized.
                //
                dir_path ld (d / path_cast<dir_path> (n));
                dir_path td (path_cast<dir_path> (followsymlink (ld)));

                const subdir* s (&next);
                for (; s != nullptr; s = s->prev)
                {
                  if (s->dir == td)
                  {
                    if (verb)
                      warn << "directory cycle caused by symlink " << ld <<
                        info << "symlink target " << td;

                    break;
                  }
                }

                if (s != nullptr)
                  break;
              }

              add_subdir (rs, sd / path_cast<dir_path> (n), files, &next);
            }
            else
              files.push_back (add_target<file> (rs, sd / n, true, true));
          }
          catch (const system_error& e)
          {
            fail << "unable to stat " << (d / n) << ": " << e;
          }
        }
      }
      catch (const system_error& e)
      {
        fail << "unable to iterate over " << d << ": " << e;
      }
    }

    // If tgt is NULL, then this is the bootstrap mode.
    //
    static void
    dist_project (const scope& rs, const target* tgt, bool prog)
    {
      tracer trace ("dist::dist_project");

      context& ctx (rs.ctx);

      const dir_path& out_root (rs.out_path ());
      const dir_path& src_root (rs.src_path ());

      // Make sure we have the necessary configuration before we get down to
      // business.
      //
      auto l (rs.vars["dist.root"]);

      if (!l || l->empty ())
        fail << "unknown root distribution directory" <<
          info << "did you forget to specify config.dist.root?";

      // We used to complain if dist.root does not exist but then, similar
      // to install, got tired of user's complaints. So now we just let
      // install -d for the package directory create it if necessary.
      //
      const dir_path& dist_root (cast<dir_path> (l));

      l = rs.vars["dist.package"];

      if (!l || l->empty ())
        fail << "unknown distribution package name" <<
          info << "did you forget to set dist.package?";

      const module& mod (*rs.find_module<module> (module::name));

      const string& dist_package (cast<string> (l));
      const process_path* dist_cmd (
        cast_null<process_path> (rs.vars["dist.cmd"]));

      dir_path td (dist_root / dir_path (dist_package));

      // We used to print 'dist <target>' at verbosity level 1 but that has
      // proven to be just noise. Though we still want to print something
      // since otherwise, once the progress line is cleared, we may end up
      // with nothing printed at all.
      //
      // Note that because of this we can also suppress diagnostics noise
      // (e.g., output directory creation) in all the operations below.
      //
      if (verb == 1)
        print_diag ("dist", src_root, td);

      // Get the list of files to distribute.
      //
      action_targets files;

      const variable* dist_var (nullptr);
      if (tgt != nullptr)
      {
        l5 ([&]{trace << "load dist " << rs;});

        dist_var = rs.var_pool ().find ("dist");

        // Match a rule for every operation supported by this project. Skip
        // default_id.
        //
        // Note that we are not calling operation_pre/post() callbacks here
        // since the meta operation is dist and we know what we are doing.
        //
        path_name pn ("<dist>");
        const location loc (pn); // Dummy location.
        action_targets ts {tgt};

        auto process_postponed = [&ctx, &mod] ()
        {
          if (!mod.postponed.list.empty ())
          {
            // Re-grab the phase lock similar to perform_match().
            //
            phase_lock l (ctx, run_phase::match);

            // Note that we don't need to bother with the mutex since we do
            // all of this serially. But we can end up with new elements at
            // the end.
            //
            // Strictly speaking, to handle this correctly we would need to do
            // multiple passes over this list and only give up when we cannot
            // make any progress since earlier entries that we cannot resolve
            // could be "fixed" by later entries. But this feels far-fetched
            // and so let's wait for a real example before complicating this.
            //
            for (auto i (mod.postponed.list.begin ());
                 i != mod.postponed.list.end ();
                 ++i)
              rule::match_postponed (*i);
          }
        };

        auto mog = make_guard ([&ctx] () {ctx.match_only = nullopt;});
        ctx.match_only = match_only_level::all;

        const operations& ops (rs.root_extra->operations);
        for (operations::size_type id (default_id + 1); // Skip default_id.
             id < ops.size ();
             ++id)
        {
          if (const operation_info* oif = ops[id])
          {
            // Skip aliases (e.g., update-for-install). In fact, one can argue
            // the default update should be sufficient since it is assumed to
            // update all prerequisites and we no longer support ad hoc stuff
            // like test.input. Though here we are using the dist
            // meta-operation, not perform.
            //
            if (oif->id != id)
              continue;

            // Use standard (perform) match.
            //
            if (auto pp = oif->pre_operation)
            {
              if (operation_id pid = pp (ctx, {}, dist_id, loc))
              {
                const operation_info* poif (ops[pid]);
                ctx.current_operation (*poif, oif, false /* diag_noise */);

                if (oif->operation_pre != nullptr)
                  oif->operation_pre (ctx, {}, false /* inner */, loc);

                if (poif->operation_pre != nullptr)
                  poif->operation_pre (ctx, {}, true /* inner */, loc);

                action a (dist_id, poif->id, oif->id);
                mod.postponed.list.clear ();
                perform_match ({}, a, ts,
                               1     /* diag (failures only) */,
                               false /* progress */);
                process_postponed ();

                if (poif->operation_post != nullptr)
                  poif->operation_post (ctx, {}, true /* inner */);

                if (oif->operation_post != nullptr)
                  oif->operation_post (ctx, {}, false /* inner */);
              }
            }

            ctx.current_operation (*oif, nullptr, false /* diag_noise */);

            if (oif->operation_pre != nullptr)
              oif->operation_pre (ctx, {}, true /* inner */, loc);

            action a (dist_id, oif->id);
            mod.postponed.list.clear ();
            perform_match ({}, a, ts,
                           1     /* diag (failures only) */,
                           false /* progress */);
            process_postponed ();

            if (oif->operation_post != nullptr)
              oif->operation_post (ctx, {}, true /* inner */);

            if (auto po = oif->post_operation)
            {
              if (operation_id pid = po (ctx, {}, dist_id))
              {
                const operation_info* poif (ops[pid]);
                ctx.current_operation (*poif, oif, false /* diag_noise */);

                if (oif->operation_pre != nullptr)
                  oif->operation_pre (ctx, {}, false /* inner */, loc);

                if (poif->operation_pre != nullptr)
                  poif->operation_pre (ctx, {}, true /* inner */, loc);

                action a (dist_id, poif->id, oif->id);
                mod.postponed.list.clear ();
                perform_match ({}, a, ts,
                               1     /* diag (failures only) */,
                               false /* progress */);
                process_postponed ();

                if (poif->operation_post != nullptr)
                  poif->operation_post (ctx, {}, true /* inner */);

                if (oif->operation_post != nullptr)
                  oif->operation_post (ctx, {}, false /* inner */);
              }
            }
          }
        }

        // Add ad hoc files and buildfiles that are not normally loaded as
        // part of the project, for example, the export stub. They will still
        // be ignored on the next step if the user explicitly marked them
        // with dist=false.
        //
        auto add_adhoc = [] (const scope& rs)
        {
          add_target<buildfile> (rs, rs.root_extra->export_file);

          if (auto* m = rs.find_module<module> (module::name))
          {
            for (const path& f: m->adhoc)
            {
              if (!path_pattern (f))
                add_target<file> (rs, f);
              else
              try
              {
                path_search (f,
                             [&rs] (path&& pe, const string&, bool interm)
                             {
                               if (!interm)
                                 add_target<file> (rs, pe, true /* exists */);

                               return true;
                             },
                             rs.src_path (),
                             path_match_flags::none /* no follow_symlinks */);
              }
              catch (const system_error& e)
              {
                fail << "unable to scan " << rs.src_path () / f.directory ()
                     << ": " << e;
              }
            }
          }
        };

        add_adhoc (rs);

        // The same for subprojects that have been loaded.
        //
        if (const subprojects* ps = *rs.root_extra->subprojects)
        {
          for (auto p: *ps)
          {
            const dir_path& pd (p.second);
            dir_path out_nroot (out_root / pd);
            const scope& nrs (ctx.scopes.find_out (out_nroot));

            if (nrs.out_path () != out_nroot) // This subproject is not loaded.
              continue;

            if (!nrs.src_path ().sub (src_root)) // Not a strong amalgamation.
              continue;

            add_adhoc (nrs);
          }
        }

        // Collect the files. We want to take the snapshot of targets since
        // updating some of them may result in more targets being entered.
        //
        // Note that we are not showing progress here (e.g., "N targets to
        // distribute") since it will be useless (too fast).
        //
        auto see_through = [] (const target& t)
        {
          return ((t.type ().flags & target_type::flag::see_through) ==
                  target_type::flag::see_through);
        };

        auto collect = [&trace, &dist_var,
                        &src_root, &out_root] (const file& ft)
        {
          if (ft.dir.sub (src_root))
          {
            // Include unless explicitly excluded.
            //
            if (const path* v = cast_null<path> (ft[dist_var]))
            {
              if (v->string () == "false")
              {
                l5 ([&]{trace << "excluding " << ft;});
                return false;
              }
            }

            return true;
          }
          else if (ft.dir.sub (out_root))
          {
            // Exclude unless explicitly included.
            //
            if (const path* v = cast_null<path> (ft[dist_var]))
            {
              if (v->string () != "false")
              {
                l5 ([&]{trace << "including " << ft;});
                return true;
              }
            }

            return false;
          }
          else
            return false; // Out of project.
        };

        for (const auto& pt: ctx.targets)
        {
          // Collect see-through groups if they are marked with dist=true.
          //
          // Note that while it's possible that only their certain members are
          // marked as such (e.g., via a pattern), we will still require
          // dist=true on the group itself (and potentially dist=false on some
          // of its members) for such cases because we don't want to update
          // every see-through group only to discover that most of them don't
          // have anything to distribute.
          //
          if (see_through (*pt))
          {
            if (const path* v = cast_null<path> ((*pt)[dist_var]))
            {
              if (v->string () != "false")
              {
                l5 ([&]{trace << "including group " << *pt;});
                files.push_back (pt.get ());
              }
            }

            continue;
          }

          file* ft (pt->is_a<file> ());

          if (ft == nullptr) // Not a file.
            continue;

          // Skip member of see-through groups since after dist_* their list
          // can be incomplete (or even bogus, e.g., the "representative
          // sample"). Instead, we will collect them during perfrom_update
          // below.
          //
          if (ft->group != nullptr && see_through (*ft->group))
            continue;

          if (collect (*ft))
            files.push_back (ft);
        }

        // Make sure what we need to distribute is up to date.
        //
        {
          if (mo_perform.meta_operation_pre != nullptr)
            mo_perform.meta_operation_pre (ctx, {}, loc);

          // This is a hack since according to the rules we need to completely
          // reset the state. We could have done that (i.e., saved target
          // names and then re-searched them in the new tree) but that would
          // just slow things down while this little cheat seems harmless
          // (i.e., assume the dist mete-opreation is "compatible" with
          // perform).
          //
          // Note also that we don't do any structured result printing.
          //
          size_t on (ctx.current_on);
          ctx.current_meta_operation (mo_perform);
          ctx.current_on = on + 1;

          if (mo_perform.operation_pre != nullptr)
            mo_perform.operation_pre (ctx, {}, update_id);

          ctx.current_operation (op_update, nullptr, false /* diag_noise */);

          if (op_update.operation_pre != nullptr)
            op_update.operation_pre (ctx, {}, true /* inner */, loc);

          action a (perform_update_id);

          mo_perform.match   ({}, a, files,
                              1    /* diag (failures only) */,
                              prog /* progress */);

          mo_perform.execute ({}, a, files,
                              1    /* diag (failures only) */,
                              prog /* progress */);

          // Replace see-through groups (which now should have their members
          // resolved) with members.
          //
          for (auto i (files.begin ()); i != files.end (); )
          {
            const target& t (i->as<target> ());
            if (see_through (t))
            {
              group_view gv (t.group_members (a)); // Go directly.

              if (gv.members == nullptr)
                fail << "unable to resolve see-through group " << t
                     << " members";

              i = files.erase (i); // Drop the group itself.

              for (size_t j (0); j != gv.count; ++j)
              {
                if (const target* m = gv.members[j])
                {
                  if (const file* ft = m->is_a<file> ())
                  {
                    // Note that a rule may only link-up its members to groups
                    // if/when matched (for example, the cli.cxx{} group). It
                    // feels harmless for us to do the linking here.
                    //
                    if (ft->group == nullptr)
                      const_cast<file*> (ft)->group = &t;
                    else
                      assert (ft->group == &t); // Sanity check.

                    if (collect (*ft))
                    {
                      i = files.insert (i, ft); // Insert instead of the group.
                      i++;                      // Stay after the group.
                    }
                  }
                }
              }
            }
            else
              ++i;
          }

          if (op_update.operation_post != nullptr)
            op_update.operation_post (ctx, {}, true /* inner */);

          if (mo_perform.operation_post != nullptr)
            mo_perform.operation_post (ctx, {}, update_id);

          if (mo_perform.meta_operation_post != nullptr)
            mo_perform.meta_operation_post (ctx, {});
        }
      }
      else
      {
        l5 ([&]{trace << "bootstrap dist " << rs;});

        // Recursively enter/collect file targets in src_root ignoring those
        // that start with a dot.
        //
        // Note that, in particular, we also collect the symlinks which point
        // outside src_root (think of third-party project packaging with the
        // upstream git submodule at the root of the git project). Also note
        // that we could probably exclude symlinks which point outside the VCS
        // project (e.g., backlinks in a forwarded configuration) but that
        // would require the user to supply this boundary (since we don't have
        // the notion of VCS root at this level). So let's keep it simple for
        // now.
        //
        add_subdir (rs, dir_path (), files);
      }

      // Apply project environment.
      //
      auto_project_env penv (rs);

      // Clean up the target directory.
      //
      if (rmdir_r (ctx, td, true, 2) == rmdir_status::not_empty)
        fail << "unable to clean target directory " << td;

      auto_rmdir rm_td (td); // Clean it up if things go bad.
      install (dist_cmd, ctx, td);

      // Copy over all the files. Apply post-processing callbacks.
      //
      prog = prog && show_progress (1 /* max_verb */);
      size_t prog_percent (0);

      for (size_t i (0), n (files.size ()); i != n; ++i)
      {
        const file& t (files[i].as<target> ().as<file> ()); // Only files.

        // Figure out where this file is inside the target directory.
        //
        // First see if the path has been remapped (unless bootstrap).
        //
        const path* rp (nullptr);
        if (tgt != nullptr)
        {
          if ((rp = cast_null<path> (t[dist_var])) != nullptr)
          {
            if (rp->string () == "true") // Wouldn't be here if false.
              rp = nullptr;
          }
        }

        bool src;
        path rn;
        dir_path dl;
        if (rp == nullptr)
        {
          src = t.dir.sub (src_root);
          dl = src ? t.dir.leaf (src_root) : t.dir.leaf (out_root);
        }
        else
        {
          // Sort the remapped path into name (if any) and directory,
          // completing the latter if relative.
          //
          bool n (!rp->to_directory ());

          if (n)
          {
            if (rp->simple ())
            {
              fail << "expected true, false, of path in the dist variable "
                   << "value of target " << t <<
                info << "specify ./" << *rp << " to remap the name";
            }

            rn = rp->leaf ();
          }

          dir_path rd (n ? rp->directory () : path_cast<dir_path> (*rp));

          if (rd.relative ())
            rd = t.dir / rd;

          rd.normalize ();

          src = rd.sub (src_root);
          dl = src ? rd.leaf (src_root) : rd.leaf (out_root);
        }

        dir_path d (td / dl);
        if (!exists (d))
          install (dist_cmd, ctx, d);

        path r (install (dist_cmd, t, d, rn));

        // See if this file is in a subproject.
        //
        const scope* srs (&rs);
        const module::callbacks* cbs (&mod.callbacks_);

        if (const subprojects* ps = *rs.root_extra->subprojects)
        {
          for (auto p: *ps)
          {
            const dir_path& pd (p.second);
            if (dl.sub (pd))
            {
              srs = &ctx.scopes.find_out (out_root / pd);

              if (auto* m = srs->find_module<module> (module::name))
                cbs = &m->callbacks_;
              else
                fail << "dist module not loaded in subproject " << pd;

              break;
            }
          }
        }

        for (module::callback cb: *cbs)
        {
          const path& pat (cb.pattern);

          // If we have a directory, then it should be relative to the project
          // root.
          //
          if (!pat.simple ())
          {
            assert (pat.relative ());

            dir_path d ((src ? srs->src_path () : srs->out_path ()) /
                        pat.directory ());
            d.normalize ();

            if (d != t.dir)
              continue;
          }

          if (path_match (t.path ().leaf ().string (), pat.leaf ().string ()))
          {
            auto_project_env penv (*srs);
            cb.function (r, *srs, cb.data);
          }
        }

        if (prog)
        {
          // Note that this is not merely an optimization since if stderr is
          // not a terminal, we print real lines for progress.
          //
          size_t p ((i * 100) / n);

          if (prog_percent != p)
          {
            prog_percent = p;

            diag_progress_lock pl;
            diag_progress  = ' ';
            diag_progress += to_string (prog_percent);
            diag_progress += "% of targets distributed";
          }
        }
      }

      // Clear the progress if shown.
      //
      if (prog)
      {
        diag_progress_lock pl;
        diag_progress.clear ();
      }

      rm_td.cancel ();

      // Archive and checksum if requested.
      //
      if (lookup as = rs.vars["dist.archives"])
      {
        lookup cs (rs.vars["dist.checksums"]);

        // Split the dist.{archives,checksums} value into a directory and
        // extension.
        //
        auto split = [] (const path& p, const dir_path& r, const char* what)
        {
          dir_path d (p.relative () ? r : dir_path ());
          d /= p.directory ();

          const string& s (p.string ());
          size_t i (path::traits_type::find_leaf (s));

          if (i == string::npos)
            fail << "invalid extension '" << s << "' in " << what;

          if (s[i] == '.') // Skip the dot if specified.
            ++i;

          return pair<dir_path, string> (move (d), string (s, i));
        };

        for (const path& p: cast<paths> (as))
        {
          auto ap (split (p, dist_root, "dist.archives"));
          path a (archive (ctx, dist_root, dist_package, ap.first, ap.second));

          if (cs)
          {
            for (const path& p: cast<paths> (cs))
            {
              auto cp (split (p, ap.first, "dist.checksums"));
              checksum (ctx, a, cp.first, cp.second);
            }
          }
        }
      }
    }

    static void
    dist_load_execute (const values&, action, action_targets& ts,
                       uint16_t, bool prog)
    {
      // We cannot do multiple projects because we need to start with a clean
      // set of targets.
      //
      if (ts.size () != 1)
        fail << "multiple targets in dist meta-operation" <<
          info << "one dist meta-operation can handle one project" <<
          info << "consider using several dist meta-operations";

      const target& t (ts[0].as<target> ());
      const scope* rs (t.base_scope ().root_scope ());

      if (rs == nullptr   ||
          !t.is_a<dir> () ||
          (rs->out_path () != t.dir && rs->src_path () != t.dir))
        fail << "dist meta-operation target must be project root directory";

      if (rs->out_eq_src ())
        fail << "in source distribution of target " << t <<
          info << "distribution requires out of source build";

      dist_project (*rs, &t, prog);
    }

    // install -d <dir>
    //
    static void
    install (const process_path* cmd, context& ctx, const dir_path& d)
    {
      path reld;
      cstrings args;

      if (cmd != nullptr || verb >= 2)
      {
        reld = relative (d);

        args.push_back (cmd != nullptr ? cmd->recall_string () : "install");
        args.push_back ("-d");
        args.push_back ("-m");
        args.push_back ("755");
        args.push_back (reld.string ().c_str ());
        args.push_back (nullptr);

        if (verb >= 2)
          print_process (args);
      }

      if (cmd != nullptr)
        run (ctx, *cmd, args, 1 /* finish_verbosity */);
      else
      {
        try
        {
          // Note that mode has no effect on Windows, which is probably for
          // the best.
          //
          try_mkdir_p (d, 0755);
        }
        catch (const system_error& e)
        {
          fail << "unable to create directory " << d << ": " << e;
        }
      }
    }

    // install <file> <dir>[/<name>]
    //
    static path
    install (const process_path* cmd,
             const file& t,
             const dir_path& d,
             const path& n)
    {
      const path& f (t.path ());
      path r (d / (n.empty () ? f.leaf () : n));

      // Assume the file is executable if the owner has execute permission,
      // in which case we make it executable for everyone.
      //
      bool exe ((path_perms (f) & permissions::xu) == permissions::xu);

      path relf, reld;
      cstrings args;

      if (cmd != nullptr || verb >= 2)
      {
        relf = relative (f);
        reld = relative (d);

        if (!n.empty ()) // Leave as just directory if no custom name.
          reld /= n;

        args.push_back (cmd != nullptr ? cmd->recall_string () : "install");

        // Preserve timestamps. This could becomes important if, for example,
        // we have pre-generated sources. Note that the install-sh script
        // doesn't support this option, while both Linux and BSD install's do.
        //
        args.push_back ("-p");

        // Assume the file is executable if the owner has execute permission,
        // in which case we make it executable for everyone.
        //
        args.push_back ("-m");
        args.push_back (exe ? "755" : "644");
        args.push_back (relf.string ().c_str ());
        args.push_back (reld.string ().c_str ());
        args.push_back (nullptr);

        if (verb >= 2)
          print_process (args);
      }

      if (cmd != nullptr)
        run (t.ctx, *cmd, args, 1 /* finish_verbosity */);
      else
      {
        permissions perm (permissions::ru | permissions::wu |
                          permissions::rg |
                          permissions::ro); // 644
        if (exe)
          perm |= permissions::xu | permissions::xg | permissions::xo; // 755

        try
        {
          // Note that we don't pass cpflags::overwrite_content which means
          // this will fail if the file already exists. Since we clean up the
          // destination directory, this will detect cases where we have
          // multiple source files with the same distribution destination.
          //
          cpfile (f,
                  r,
                  cpflags::overwrite_permissions | cpflags::copy_timestamps,
                  perm);
        }
        catch (const system_error& e)
        {
          if (e.code ().category () == generic_category () &&
              e.code ().value () == EEXIST)
          {
            // @@ TMP (added in 0.16.0).
            //
            warn << "multiple files are distributed as " << r <<
              info << "second file is " << f <<
              info << "this warning will become error in the future";
          }
          else
            fail << "unable to copy " << f << " to " << r << ": " << e;
        }
      }

      return r;
    }

    static path
    archive (context& ctx,
             const dir_path& root,
             const string& pkg,
             const dir_path& dir,
             const string& e)
    {
      // NOTE: similar code in bpkg (system-package-manager-archive.cxx).

      path an (pkg + '.' + e);

      // Delete old archive for good measure.
      //
      path ap (dir / an);
      if (exists (ap, false))
        rmfile (ctx, ap, 3 /* verbosity */);

      // Use zip for .zip archives. Also recognize and handle a few well-known
      // tar.xx cases (in case tar doesn't support -a or has other issues like
      // MSYS). Everything else goes to tar in the auto-compress mode (-a).
      //
      cstrings args;

      // Separate compressor (gzip, xz, etc) state.
      //
      size_t i (0);        // Command line start or 0 if not used.
      auto_rmfile out_rm;  // Output file cleanup (must come first).
      auto_fd out_fd;      // Output file.

      if (e == "zip")
      {
        // On Windows we use libarchive's bsdtar (zip is an MSYS executable).
        //
        // While not explicitly stated, the compression-level option works
        // for zip archives.
        //
#ifdef _WIN32
        args = {"bsdtar",
                "-a", // -a with the .zip extension seems to be the only way.
                "--options=compression-level=9",
                "-cf", ap.string ().c_str (),
                pkg.c_str (),
                nullptr};
#else
        args = {"zip",
                "-9",
                "-rq", ap.string ().c_str (),
                pkg.c_str (),
                nullptr};
#endif
      }
      else
      {
        // On Windows we use libarchive's bsdtar with auto-compression (tar
        // itself and quite a few compressors are MSYS executables).
        //
        // OpenBSD tar does not support --format but it appear ustar is the
        // default (while this is not said explicitly in tar(1), it is said in
        // pax(1) and confirmed on the mailing list). Nor does it support -a,
        // at least as of 7.1 but we will let this play out naturally, in case
        // this support gets added.
        //
        // Note also that our long-term plan is to switch to libarchive in
        // order to generate reproducible archives.
        //
        const char* l (nullptr); // Compression level (option).

#ifdef _WIN32
        args = {"bsdtar", "--format", "ustar"};

        if (e == "tar.gz")
          l = "--options=compression-level=9";
#else
        args = {"tar"
#ifndef __OpenBSD__
                , "--format", "ustar"
#endif
        };

        // For gzip it's a good idea to use -9 by default. For bzip2, -9 is
        // the default. And for xz, -9 is not recommended as the default due
        // memory requirements.
        //
        // Note also that the compression level can be altered via the GZIP
        // (GZIP_OPT also seems to work), BZIP2, and XZ_OPT environment
        // variables, respectively.
        //
        const char* c (nullptr);

        if      (e == "tar.gz")  { c = "gzip";  l = "-9"; }
        else if (e == "tar.xz")  { c = "xz";              }
        else if (e == "tar.bz2") { c = "bzip2";           }

        if (c != nullptr)
        {
          args.push_back ("-cf");
          args.push_back ("-");
          args.push_back (pkg.c_str ());
          args.push_back (nullptr); i = args.size ();
          args.push_back (c);
          if (l != nullptr)
            args.push_back (l);
          args.push_back (nullptr);
          args.push_back (nullptr); // Pipe end.

          try
          {
            out_fd = fdopen (ap,
                             fdopen_mode::out      | fdopen_mode::binary |
                             fdopen_mode::truncate | fdopen_mode::create);
            out_rm = auto_rmfile (ap);
          }
          catch (const io_error& e)
          {
            fail << "unable to open " << ap << ": " << e;
          }
        }
        else
#endif
        {
          if (e != "tar")
          {
            args.push_back ("-a");
            if (l != nullptr)
              args.push_back (l);
          }

          args.push_back ("-cf");
          args.push_back (ap.string ().c_str ());
          args.push_back (pkg.c_str ());
          args.push_back (nullptr);
        }
      }

      process_path app; // Archiver path.
      process_path cpp; // Compressor path.

      app = run_search (args[0]);

      if (i != 0)
        cpp = run_search (args[i]);

      if (verb >= 2)
        print_process (args);
      else if (verb)
        print_diag (args[0], dir / dir_path (pkg), ap);

      process apr;
      process cpr;

      // Change the archiver's working directory to root.
      //
      // Note: this function is called during serial execution and so no
      // diagnostics buffering is needed (here and below).
      //
      apr = run_start (process_env (app, root),
                       args,
                       0                 /* stdin  */,
                       (i != 0 ? -1 : 1) /* stdout */);

      // Start the compressor if required.
      //
      if (i != 0)
      {
        cpr = run_start (cpp,
                         args.data () + i,
                         apr.in_ofd.get () /* stdin  */,
                         out_fd.get ()     /* stdout */);

        cpr.in_ofd.reset (); // Close the archiver's stdout on our side.
      }

      // Delay throwing until we diagnose both ends of the pipe.
      //
      if (!run_finish_code (args.data (),
                            apr,
                            1     /* verbosity */,
                            false /* omit_normal */) ||
          !(i == 0 || run_finish_code (args.data () + i, cpr, 1, false)))
        throw failed ();


      out_rm.cancel ();
      return ap;
    }

    static path
    checksum (context& ctx,
              const path& ap, const dir_path& dir, const string& e)
    {
      path     an (ap.leaf ());
      dir_path ad (ap.directory ());

      path cn (an + '.' + e);

      // Delete old checksum for good measure.
      //
      path cp (dir / cn);
      if (exists (cp, false))
        rmfile (ctx, cp, 3 /* verbosity */);

      auto_rmfile c_rm; // Note: must come first.
      auto_fd c_fd;
      try
      {
        c_fd = fdopen (cp,
                       fdopen_mode::out     |
                       fdopen_mode::create  |
                       fdopen_mode::truncate);
        c_rm = auto_rmfile (cp);
      }
      catch (const io_error& e)
      {
        fail << "unable to open " << cp << ": " << e;
      }

      // The plan is as follows: look for the <ext>sum program (e.g., sha1sum,
      // md5sum, etc). If found, then use that, otherwise, fall back to our
      // built-in checksum calculation support.
      //
      // There are two benefits to first trying the external program: it may
      // supports more checksum algorithms and could be faster than our
      // built-in code.
      //
      string pn (e + "sum");
      process_path pp (process::try_path_search (pn, true /* init */));

      if (!pp.empty ())
      {
        const char* args[] {
          pp.recall_string (),
          "-b" /* binary */,
          an.string ().c_str (),
          nullptr};

        if (verb >= 2)
          print_process (args);
        else if (verb)
          print_diag (args[0], ap, cp);

        // Note that to only get the archive name (without the directory) in
        // the output we have to run from the archive's directory.
        //
        // Note: this function is called during serial execution and so no
        // diagnostics buffering is needed.
        //
        process pr (run_start (process_env (pp, ad /* cwd */),
                               args,
                               0             /* stdin  */,
                               c_fd.get ()   /* stdout */));

        run_finish (args, pr, 1 /* verbosity */);
      }
      else
      {
        string (*f) (ifdstream&);

        // Note: remember to update info: below if adding another algorithm.
        //
        if (e == "sha1")
          f = [] (ifdstream& i) -> string {return sha1 (i).string ();};
        else if (e == "sha256")
          f = [] (ifdstream& i) -> string {return sha256 (i).string ();};
        else
          fail << "no built-in support for checksum algorithm " << e
               << " nor " << e << "sum program found" <<
            info << "built-in support is available for sha1, sha256" << endf;

        if (verb >= 2)
          text << "cat >" << cp;
        else if (verb)
          print_diag ((e + "sum").c_str (), ap, cp);

        string c;
        try
        {
          ifdstream is (ap, fdopen_mode::in | fdopen_mode::binary);
          c = f (is);
          is.close ();
        }
        catch (const io_error& e)
        {
          fail << "unable to read " << ap << ": " << e;
        }

        try
        {
          ofdstream os (move (c_fd));
          os << c << " *" << an << endl;
          os.close ();
        }
        catch (const io_error& e)
        {
          fail << "unable to write to " << cp << ": " << e;
        }
      }

      c_rm.cancel ();
      return cp;
    }

    static include_type
    dist_include (action,
                  const target&,
                  const prerequisite_member& p,
                  include_type i,
                  lookup& l)
    {
      tracer trace ("dist::dist_include");

      // Override excluded to adhoc so that every source is included into the
      // distribution. Note that this should be harmless to a custom rule
      // given the prescribed semantics of adhoc (match/execute but otherwise
      // ignore) is followed.
      //
      // Note that we don't need to do anything for posthoc.
      //
      if (i == include_type::excluded)
      {
        l5 ([&]{trace << "overriding exclusion of " << p;});
        i = include_type::adhoc;
      }

      // Also clear any operation-specific overrides.
      //
      l = lookup ();

      return i;
    }

    const meta_operation_info mo_dist_load {
      dist_id,
      "dist",
      "distribute",
      "distributing",
      "distributed",
      "has nothing to distribute", // We cannot "be distributed".
      true,    // bootstrap_outer
      nullptr, // meta-operation pre
      &dist_operation_pre,
      &dist_load_load,
      &perform_search,    // normal search
      nullptr,            // no match (see dist_execute()).
      &dist_load_execute,
      nullptr,            // operation post
      nullptr,            // meta-operation post
      &dist_include
    };

    // The bootstrap distribution mode.
    //
    // Note: pretty similar overall idea as the info meta-operation.
    //
    void
    init_config (scope&); // init.cxx

    static void
    dist_bootstrap_load (const values&,
                         scope& rs,
                         const path&,
                         const dir_path& out_base,
                         const dir_path& src_base,
                         const location& l)
    {
      if (rs.out_path () != out_base || rs.src_path () != src_base)
        fail (l) << "dist meta-operation target must be project root directory";

      setup_base (rs.ctx.scopes.rw (rs).insert_out (out_base),
                  out_base,
                  src_base);

      // Also initialize the dist.* variables (needed in dist_project()).
      //
      init_config (rs);
    }

    static void
    dist_bootstrap_search (const values&,
                           const scope& rs,
                           const scope&,
                           const path&,
                           const target_key& tk,
                           const location& l,
                           action_targets& ts)
    {
      if (!tk.type->is_a<dir> ())
        fail (l) << "dist meta-operation target must be project root directory";

      ts.push_back (&rs);
    }

    static void
    dist_bootstrap_execute (const values&, action, action_targets& ts,
                            uint16_t, bool prog)
    {
      for (const action_target& at: ts)
        dist_project (at.as<scope> (), nullptr, prog);
    }

    const meta_operation_info mo_dist_bootstrap {
      dist_id,
      "dist",
      "distribute",
      "distributing",
      "distributed",
      "has nothing to distribute",
      true,    // bootstrap_outer //@@ Maybe not? (But will overrides work)?
      nullptr, // meta-operation pre
      &dist_operation_pre,
      &dist_bootstrap_load,
      &dist_bootstrap_search,
      nullptr, // no match (see dist_bootstrap_execute()).
      &dist_bootstrap_execute,
      nullptr, // operation post
      nullptr, // meta-operation post
      nullptr  // include
    };
  }
}