-----------------------------------------------------------------------------
-- Xavante File handler
--
-- Authors: Javier Guerra and Andre Carregal
-- Copyright (c) 2004-2007 Kepler Project
--
-- $Id: filehandler.lua,v 1.26 2009/08/11 01:48:07 mascarenhas Exp $
----------------------------------------------------------------------------

local lfs = require "lfs"
local url = require "socket.url"
local mime = require "xavante.mime"
local enc = require "xavante.encoding"
local xavante = require "xavante"
local httpd = require "xavante.httpd"

xavante.mimetypes = xavante.mimetypes or {}
xavante.encodings = xavante.encodings or {}

-- gets the mimetype from the filename's extension
local function mimefrompath (path)
        local _,_,exten = string.find (path, "%.([^.]*)$")
        if exten then
                return xavante.mimetypes [exten]
        else
                return nil
        end
end

-- gets the encoding from the filename's extension
local function encodingfrompath (path)
        local _,_,exten = string.find (path, "%.([^.]*)$")
        if exten then
                return xavante.encodings [exten]
        else
                return nil
        end
end

-- on partial requests seeks the file to
-- the start of the requested range and returns
-- the number of bytes requested.
-- on full requests returns nil
local function getrange (req, f)
        local range = req.headers["range"]
        if not range then return nil end

        local s,e, r_A, r_B = string.find (range, "(%d*)%s*-%s*(%d*)")
        if s and e then
                r_A = tonumber (r_A)
                r_B = tonumber (r_B)

                if r_A then
                        f:seek ("set", r_A)
                        if r_B then return r_B + 1 - r_A end
                else
                        if r_B then f:seek ("end", - r_B) end
                end
        end

        return nil
end

-- sends data from the open file f
-- to the response object res
-- sends only numbytes, or until the end of f
-- if numbytes is nil
local function sendfile (f, res, numbytes)
        local block
        local whole = not numbytes
        local left = numbytes
        local blocksize = 8192

        if not whole then blocksize = math.min (blocksize, left) end

        while whole or left > 0 do
                block = f:read (blocksize)
                if not block then return end
                if not whole then
                        left = left - string.len (block)
                        blocksize = math.min (blocksize, left)
                end
                res:send_data (block)
        end
end

local function in_base(path)
  local l = 0
  if path:sub(1, 1) ~= "/" then path = "/" .. path end
  for dir in path:gmatch("/([^/]+)") do
    if dir == ".." then
      l = l - 1
    elseif dir ~= "." then
      l = l + 1
    end
    if l < 0 then return false end
  end
  return true
end

-- main handler
local function filehandler (req, res, baseDir)

        if req.cmd_mth ~= "GET" and req.cmd_mth ~= "HEAD" then
                return httpd.err_405 (req, res)
        end

        if not in_base(req.relpath) then
                return httpd.err_403 (req, res)
        end

        local path = baseDir .."/".. req.relpath

        res.headers ["Content-Type"] = mimefrompath (path)
        res.headers ["Content-Encoding"] = encodingfrompath (path)

        local attr = lfs.attributes (path)
        if not attr then
                return httpd.err_404 (req, res)
        end
        assert (type(attr) == "table")

        if attr.mode == "directory" then
                req.parsed_url.path = req.parsed_url.path .. "/"
                res.statusline = "HTTP/1.1 301 Moved Permanently"
                res.headers["Location"] = url.build (req.parsed_url)
                res.content = "redirect"
                return res
        end

        res.headers["Content-Length"] = attr.size

        local f = io.open (path, "rb")
        if not f then
                return httpd.err_404 (req, res)
        end

        res.headers["last-modified"] = os.date ("!%a, %d %b %Y %H:%M:%S GMT",
                                        attr.modification)

        local lms = req.headers["if-modified-since"] or 0
        local lm = res.headers["last-modified"] or 1
        if lms == lm then
                res.headers["Content-Length"] = 0
                res.statusline = "HTTP/1.1 304 Not Modified"
                res.content = ""
        res.chunked = false
        res:send_headers()
        f:close()
                return res
        end


        if req.cmd_mth == "GET" then
                local range_len = getrange (req, f)
                if range_len then
                        res.statusline = "HTTP/1.1 206 Partial Content"
                        res.headers["Content-Length"] = range_len
                end

                sendfile (f, res, range_len)
        else
                res.content = ""
                res:send_headers ()
    end
    f:close ()
        return res
end


return function (baseDir)
         if type(baseDir) == "table" then baseDir = baseDir.baseDir end
         return function (req, res)
                  return filehandler (req, res, baseDir)
                end
       end