local global_env = _G
local package, require, assert, ipairs, pairs, os, print, table, type, next, unpack =
      package, require, assert, ipairs, pairs, os, print, table, type, next, unpack

module("luarocks")

local path = require("luarocks.path")
local manif_core = require("luarocks.manif_core")
local deps = require("luarocks.deps")
local cfg = require("luarocks.cfg")

context = {}

-- Contains a table when rocks trees are loaded,
-- or 'false' to indicate rocks trees failed to load.
-- 'nil' indicates rocks trees were not attempted to be loaded yet.
rocks_trees = nil

local function load_rocks_trees() 
   local any_ok = false
   local trees = {}
   
   -- FIXME select correctly file to be fetched
   local persist = require("luarocks.persist")
   table.insert(trees, { manifest = persist.load_into_table("manifest2") } )
   any_ok = true

   if not any_ok then
      rocks_trees = false
      return false
   end
   rocks_trees = trees
   return true
end

--- Process the dependencies of a package to determine its dependency
-- chain for loading modules.
-- @parse name string: The name of an installed rock.
-- @parse version string: The version of the rock, in string format
-- @parse manifest table: The local manifest table where this rock
-- is installed.
local function add_context(name, version)
   -- assert(type(name) == "string")
   -- assert(type(version) == "string")
   -- assert(type(manifest) == "table")

   if context[name] then
      return
   end
   context[name] = version
   --[[

   local pkgdeps = manifest.dependencies and manifest.dependencies[name][version]
   if not pkgdeps then
      return
   end
   for _, dep in ipairs(pkgdeps) do
      local package, constraints = dep.name, dep.constraints

      for _, tree in pairs(rocks_trees) do
         local entries = tree.manifest.repository[package]
         if entries then
            for version, packages in pairs(entries) do
               if (not constraints) or deps.match_constraints(deps.parse_version(version), constraints) then
                  add_context(package, version, tree.manifest)
               end
            end
         end
      end
   end
   ]]
end

--- Internal sorting function.
-- @param a table: A provider table.
-- @param b table: Another provider table.
-- @return boolean: True if the version of a is greater than that of b.
local function sort_versions(a,b)
   return a.version > b.version
end

local function call_other_loaders(module, name, version, file)
   
   local actual_module = file:match("(.*)%.[^.]+$")
   
   for i, loader in pairs(package.loaders) do
      if loader ~= luarocks_loader then
         local results = { loader(actual_module) }
         if type(results[1]) == "function" then
            return unpack(results)
         end
      end
   end
   return nil, "Failed loading module "..module.." in LuaRocks rock "..name.." "..version
end

local function pick_module(module)
   --assert(type(module) == "string")

   if not rocks_trees and not load_rocks_trees() then
      return nil
   end

   local providers = {}
   for _, tree in pairs(rocks_trees) do
      local entries = tree.manifest.modules[module]
      if entries then
         for entry, file in pairs(entries) do
            local name, version = entry:match("^([^/]*)/(.*)$")
            if context[name] == version then
               return name, version, file
            end
            version = deps.parse_version(version)
            table.insert(providers, {name = name, version = version, file = file})
         end
      end
   end

   if next(providers) then
      table.sort(providers, sort_versions)
      local first = providers[1]
      return first.name, first.version.string, first.file
   end
end

--- Package loader for LuaRocks support.
-- A module is searched in installed rocks that match the
-- current LuaRocks context. If module is not part of the
-- context, or if a context has not yet been set, the module
-- in the package with the highest version is used.
-- @param module string: The module name, like in plain require().
-- @return table: The module table (typically), like in plain
-- require(). See <a href="http://www.lua.org/manual/5.1/manual.html#pdf-require">require()</a>
-- in the Lua reference manual for details.

function luarocks_loader(module)
   local name, version, file = pick_module(module)
   if not name then
      return nil, "No LuaRocks module found for "..module
   else
      add_context(name, version)
      return call_other_loaders(module, name, version, file)
   end
end

table.insert(global_env.package.loaders, 1, luarocks_loader)