// file      : build/file.cxx -*- C++ -*-
// copyright : Copyright (c) 2014-2015 Code Synthesis Ltd
// license   : MIT; see accompanying LICENSE file

#include <build/file>

#include <fstream>

#include <butl/filesystem>

#include <build/scope>
#include <build/context>
#include <build/parser>
#include <build/diagnostics>

using namespace std;
using namespace butl;

namespace build
{
  bool
  is_src_root (const dir_path& d)
  {
    return file_exists (d / path ("build/bootstrap.build")) ||
      file_exists (d / path ("build/root.build"));
  }

  bool
  is_out_root (const dir_path& d)
  {
    return file_exists (d / path ("build/bootstrap/src-root.build"));
  }

  dir_path
  find_src_root (const dir_path& b)
  {
    for (dir_path d (b); !d.root () && d != home; d = d.directory ())
    {
      if (is_src_root (d))
        return d;
    }

    return dir_path ();
  }

  dir_path
  find_out_root (const dir_path& b, bool* src)
  {
    for (dir_path d (b); !d.root () && d != home; d = d.directory ())
    {
      bool s (false);
      if ((s = is_src_root (d)) || is_out_root (d)) // Order is important!
      {
        if (src != nullptr)
          *src = s;

        return d;
      }
    }

    return dir_path ();
  }

  void
  source (const path& bf, scope& root, scope& base)
  {
    tracer trace ("source");

    ifstream ifs (bf.string ());
    if (!ifs.is_open ())
      fail << "unable to open " << bf;

    level4 ([&]{trace << "sourcing " << bf;});

    ifs.exceptions (ifstream::failbit | ifstream::badbit);
    parser p;

    try
    {
      p.parse_buildfile (ifs, bf, root, base);
    }
    catch (const std::ios_base::failure&)
    {
      fail << "failed to read from " << bf;
    }
  }

  void
  source_once (const path& bf, scope& root, scope& base, scope& once)
  {
    tracer trace ("source_once");

    if (!once.buildfiles.insert (bf).second)
    {
      level4 ([&]{trace << "skipping already sourced " << bf;});
      return;
    }

    source (bf, root, base);
  }

  scope&
  create_root (const dir_path& out_root, const dir_path& src_root)
  {
    scope& rs (scopes.insert (out_root, true).first);

    // Enter built-in meta-operation and operation names. Note that
    // the order of registration should match the id constants; see
    // <operation> for details. Loading of modules (via the src
    // bootstrap; see below) can result in additional names being
    // added.
    //
    if (rs.meta_operations.empty ())
    {
      assert (rs.meta_operations.insert (perform) == perform_id);

      assert (rs.operations.insert (default_) == default_id);
      assert (rs.operations.insert (update) == update_id);
      assert (rs.operations.insert (clean) == clean_id);
    }

    // If this is already a root scope, verify that things are
    // consistent.
    //
    {
      auto v (rs.assign ("out_root"));

      if (!v)
        v = out_root;
      else
      {
        const dir_path& p (v.as<const dir_path&> ());

        if (p != out_root)
          fail << "new out_root " << out_root << " does not match "
               << "existing " << p;
      }
    }

    if (!src_root.empty ())
    {
      auto v (rs.assign ("src_root"));

      if (!v)
        v = src_root;
      else
      {
        const dir_path& p (v.as<const dir_path&> ());

        if (p != src_root)
          fail << "new src_root " << src_root << " does not match "
               << "existing " << p;
      }
    }

    return rs;
  }

  void
  bootstrap_out (scope& root)
  {
    path bf (root.path () / path ("build/bootstrap/src-root.build"));

    if (!file_exists (bf))
      return;

    //@@ TODO: if bootstrap files can source other bootstrap files
    //   (the way to express dependecies), then we need a way to
    //   prevent multiple sourcing. We handle it here but we still
    //   need something like source_once (once [scope] source).
    //
    source_once (bf, root, root);
  }

  bool
  bootstrap_src (scope& root)
  {
    tracer trace ("bootstrap_src");

    bool r (false);

    path bf (root.src_path () / path ("build/bootstrap.build"));

    if (file_exists (bf))
    {
      // We assume that bootstrap out cannot load this file explicitly. It
      // feels wrong to allow this since that makes the whole bootstrap
      // process hard to reason about. But we may try to bootstrap the
      // same root scope multiple time.
      //
      source_once (bf, root, root);
      r = true;
    }

    // See if we are a part of an amalgamation. There are two key
    // players: the outer root scope which may already be present
    // (i.e., we were loaded as part of an amalgamation) and the
    // amalgamation variable that may or may not be set by the
    // user (in bootstrap.build) or by an earlier call to this
    // function for the same scope. When set by the user, the
    // empty special value means that the project shall not be
    // amalgamated. When calculated, the NULL value indicates
    // that we are not amalgamated.
    //
    {
      auto rp (root.vars.assign("amalgamation")); // Set NULL by default.
      auto& val (rp.first);
      const dir_path& d (root.path ());

      if (scope* aroot = root.parent_scope ()->root_scope ())
      {
        const dir_path& ad (aroot->path ());
        dir_path rd (ad.relative (d));

        // If we already have the amalgamation variable set, verify
        // that aroot matches its value.
        //
        if (!rp.second)
        {
          if (val.null () || val.empty ())
          {
            fail << d << " cannot be amalgamated" <<
              info << "amalgamated by " << ad;
          }
          else
          {
            const dir_path& vd (val.as<const dir_path&> ());

            if (vd != rd)
            {
              fail << "inconsistent amalgamation of " << d <<
                info << "specified: " << vd <<
                info << "actual: " << rd << " by " << ad;
            }
          }
        }
        else
        {
          // Otherwise, use the outer root as our amalgamation.
          //
          level4 ([&]{trace << d << " amalgamated as " << rd;});
          val = move (rd);
        }
      }
      else if (rp.second)
      {
        // If there is no outer root and the amalgamation variable
        // hasn't been set, then we need to check if any of the
        // outer directories is a project's out_root. If so, then
        // that's our amalgamation.
        //
        const dir_path& d (root.path ());
        const dir_path& ad (find_out_root (d.directory ()));

        if (!ad.empty ())
        {
          dir_path rd (ad.relative (d));
          level4 ([&]{trace << d << " amalgamated as " << rd;});
          val = move (rd);
        }
      }
    }

    return r;
  }

  void
  create_bootstrap_outer (scope& root)
  {
    auto v (root.vars["amalgamation"]);

    if (!v || v.empty ())
      return;

    const dir_path& d (v.as<const dir_path&> ());
    dir_path out_root (root.path () / d);
    out_root.normalize ();

    // src_root is a bit more complicated. Here we have three cases:
    //
    // 1. Amalgamation's src_root is "parallel" to the sub-project's.
    // 2. Amalgamation's src_root is the same as its out_root.
    // 3. Some other pre-configured (via src-root.build) src_root.
    //
    // So we need to try all these cases in some sensible order.
    // #3 should probably be tried first since that src_root was
    // explicitly configured by the user. After that, #2 followed
    // by #1 seems reasonable.
    //
    scope& rs (create_root (out_root, dir_path ()));
    bootstrap_out (rs); // #3 happens here, if at all.

    auto val (rs.assign ("src_root"));

    if (!val)
    {
      if (is_src_root (out_root)) // #2
        val = out_root;
      else // #1
      {
        dir_path src_root (root.src_path () / d);
        src_root.normalize ();
        val = move (src_root);
      }
    }

    rs.src_path_ = &val.as<const dir_path&> ();

    bootstrap_src (rs);
    create_bootstrap_outer (rs);
  }

  scope&
  create_bootstrap_inner (scope& root, const dir_path& out_base)
  {
    if (auto v = root.vars["subprojects"])
    {
      for (const name& n: v.as<const list_value&> ())
      {
        // Should be a list of directories.
        //
        if (!n.directory ())
          fail << "expected directory in subprojects variable "
               << "instead of " << n;

        dir_path out_root (root.path () / n.dir);

        if (!out_base.sub (out_root))
          continue;

        // The same logic to src_root as in create_bootstrap_outer().
        //
        scope& rs (create_root (out_root, dir_path ()));
        bootstrap_out (rs);

        auto val (rs.assign ("src_root"));

        if (!val)
          val = is_src_root (out_root)
            ? out_root
            : (root.src_path () / n.dir);

        rs.src_path_ = &val.as<const dir_path&> ();

        bootstrap_src (rs);

        // See if there are more inner roots.
        //
        return create_bootstrap_inner (rs, out_base);
      }
    }

    return root;
  }

  void
  load_root_pre (scope& root)
  {
    tracer trace ("root_pre");

    // First load outer roots, if any.
    //
    if (scope* rs = root.parent_scope ()->root_scope ())
      load_root_pre (*rs);

    path bf (root.src_path () / path ("build/root.build"));

    if (file_exists (bf))
      source_once (bf, root, root);
  }

  list_value
  import (scope& ibase, const name& n, const location& l)
  {
    tracer trace ("import");

    // Split the name into the project and target.
    //
    string project;
    name target;

    if (n.dir.empty ())
    {
      if (!n.simple ())
        fail << "project name expected before imported target " << n;

      // Note that value can be foo/bar/baz; in this case probably
      // means sub-projects? Or only to a certain point, then
      // (untyped) target? Looks like I will need to scan anything
      // that looks like a directory checking if this is a subproject.
      // If not, then that's part of the target.
      //
      project = n.value;
    }
    else
    {
      //@@ This can be a path inside a sub-project. So, eventually,
      //   we should find the innermost sub-project and load the
      //   export stub from there (will probably still have to
      //   resolve root from the top-level project). For now we
      //   assume the project is always top-level.
      //
      project = *n.dir.begin ();

      target.dir = n.dir.leaf (dir_path (project));
      target.type = n.type;
      target.value = n.value;
    }

    scope& iroot (*ibase.root_scope ());

    // Figure out this project's out_root.
    //
    dir_path out_root;
    string var ("config.import." + project);

    if (auto v = iroot[var])
    {
      if (!v.belongs (*global_scope)) // A value from (some) config.build.
        out_root = v.as<const dir_path&> ();
      else
      {
        // Process the path by making it absolute and normalized. Also,
        // for usability's sake, treat a simple name that doesn't end
        // with '/' as a directory.
        //
        list_value& lv (v.as<list_value&> ());

        if (lv.size () != 1 || lv[0].empty () || !lv[0].type.empty ())
          fail (l) << "invalid " << var << " value " << lv;

        name& n (lv[0]);

        if (n.directory ())
          out_root = n.dir;
        else
          out_root = dir_path (n.value);

        if (out_root.relative ())
          out_root = work / out_root;

        out_root.normalize ();
        iroot.assign (var) = out_root;

        // Also update the command-line value. This is necessary to avoid
        // a warning issued by the config module about global/root scope
        // value mismatch.
        //
        if (n.dir != out_root)
          n = name (out_root);
      }
    }
    else
      fail (l) << "unable to find out_root for imported " << project <<
        info << "consider explicitly configuring its out_root via the "
               << var << " command line variable";

    // Bootstrap the imported root scope. This is pretty similar to
    // what we do in main() except that here we don't try to guess
    // src_root.
    //
    dir_path src_root (is_src_root (out_root) ? out_root : dir_path ());
    scope& root (create_root (out_root, src_root));

    bootstrap_out (root);

    // Check that the bootstrap process set src_root.
    //
    if (auto v = root.vars["src_root"])
    {
      const dir_path& p (v.as<const dir_path&> ());

      if (!src_root.empty () && p != src_root)
        fail << "bootstrapped src_root " << p << " does not match "
             << "discovered " << src_root;

      root.src_path_ = &p;
    }
    else
      fail (l) << "unable to determine src_root for imported " << project <<
        info << "consider configuring " << out_root;

    bootstrap_src (root);

    // Bootstrap outer roots if any. Loading will be done by
    // load_root_pre() below.
    //
    create_bootstrap_outer (root);

    // Load the imported root scope.
    //
    load_root_pre (root);

    // Create a temporary scope so that the export stub does not mess
    // up any of our variables.
    //
    temp_scope ts (ibase);

    // "Pass" the imported project's roots to the stub.
    //
    ts.assign ("out_root") = move (out_root);
    ts.assign ("src_root") = move (src_root);

    // Also pass the target being imported.
    //
    {
      auto v (ts.assign ("target"));

      if (!target.empty ()) // Otherwise leave NULL.
        v = list_value {move (target)};
    }

    // Load the export stub. Note that it is loaded in the context
    // of the importing project, not the imported one. The export
    // stub will normally switch to the imported root scope at some
    // point.
    //
    path es (root.src_path () / path ("build/export.build"));
    ifstream ifs (es.string ());
    if (!ifs.is_open ())
      fail << "unable to open " << es;

    level4 ([&]{trace << "importing " << es;});

    ifs.exceptions (ifstream::failbit | ifstream::badbit);
    parser p;

    try
    {
      p.parse_buildfile (ifs, es, iroot, ts);
    }
    catch (const std::ios_base::failure&)
    {
      fail << "failed to read from " << es;
    }

    return p.export_value ();
  }
}