--- Core functions for querying manifest files.
local manif = {}

local persist = require("luarocks.core.persist")
local cfg = require("luarocks.core.cfg")
local dir = require("luarocks.core.dir")
local util = require("luarocks.core.util")
local vers = require("luarocks.core.vers")
local path = require("luarocks.core.path")
local require = nil
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-- Table with repository identifiers as keys and tables mapping
-- Lua versions to cached loaded manifests as values.
local manifest_cache = {}

--- Cache a loaded manifest.
-- @param repo_url string: The repository identifier.
-- @param lua_version string: Lua version in "5.x" format, defaults to installed version.
-- @param manifest table: the manifest to be cached.
function manif.cache_manifest(repo_url, lua_version, manifest)
   lua_version = lua_version or cfg.lua_version
   manifest_cache[repo_url] = manifest_cache[repo_url] or {}
   manifest_cache[repo_url][lua_version] = manifest
end

--- Attempt to get cached loaded manifest.
-- @param repo_url string: The repository identifier.
-- @param lua_version string: Lua version in "5.x" format, defaults to installed version.
-- @return table or nil: loaded manifest or nil if cache is empty.
function manif.get_cached_manifest(repo_url, lua_version)
   lua_version = lua_version or cfg.lua_version
   return manifest_cache[repo_url] and manifest_cache[repo_url][lua_version]
end

--- Back-end function that actually loads the manifest
-- and stores it in the manifest cache.
-- @param file string: The local filename of the manifest file.
-- @param repo_url string: The repository identifier.
-- @param lua_version string: Lua version in "5.x" format, defaults to installed version.
-- @return table or (nil, string, string): the manifest or nil,
-- error message and error code ("open", "load", "run").
function manif.manifest_loader(file, repo_url, lua_version)
   local manifest, err, errcode = persist.load_into_table(file)
   if not manifest then
      return nil, "Failed loading manifest for "..repo_url..": "..err, errcode
   end
   manif.cache_manifest(repo_url, lua_version, manifest)
   return manifest, err, errcode
end

--- Load a local manifest describing a repository.
-- This is used by the luarocks.loader only.
-- @param repo_url string: URL or pathname for the repository.
-- @return table or (nil, string, string): A table representing the manifest,
-- or nil followed by an error message and an error code, see manifest_loader.
function manif.fast_load_local_manifest(repo_url)
   assert(type(repo_url) == "string")

   local cached_manifest = manif.get_cached_manifest(repo_url)
   if cached_manifest then
      return cached_manifest
   end

   local pathname = dir.path(repo_url, "manifest")
   return manif.manifest_loader(pathname, repo_url, nil, true)
end

function manif.load_rocks_tree_manifests(deps_mode)
   local trees = {}
   path.map_trees(deps_mode, function(tree)
      local manifest, err = manif.fast_load_local_manifest(path.rocks_dir(tree))
      if manifest then
         table.insert(trees, {tree=tree, manifest=manifest})
      end
   end)
   return trees
end

function manif.scan_dependencies(name, version, tree_manifests, dest)
   if dest[name] then
      return
   end
   dest[name] = version

   for _, tree in ipairs(tree_manifests) do
      local manifest = tree.manifest

      local pkgdeps
      if manifest.dependencies and manifest.dependencies[name] then
         pkgdeps = manifest.dependencies[name][version]
      end
      if pkgdeps then
         for _, dep in ipairs(pkgdeps) do
            local pkg, constraints = dep.name, dep.constraints

            for _, t in ipairs(tree_manifests) do
               local entries = t.manifest.repository[pkg]
               if entries then
                  for ver, _ in util.sortedpairs(entries, vers.compare_versions) do
                     if (not constraints) or vers.match_constraints(vers.parse_version(ver), constraints) then
                        manif.scan_dependencies(pkg, ver, tree_manifests, dest)
                     end
                  end
               end
            end
         end
         return
      end
   end
end

return manif