require "option_parser"
require "http/server"
require "ecr/macros"
require "./guff/*"

module Guff
  class Config
    property :mode, :env, :host, :port, :data_dir, :assets_dir

    DEFAULTS = {
      mode:       "help",
      env:        "production",
      host:       "127.0.0.1",
      port:       "8989",
      data_dir:   "./data",
      assets_dir: "/usr/local/share/guff",
    }

    def initialize
      @mode        = DEFAULTS[:mode] as String
      @env         = (ENV["GUFF_ENVIRONMENT"]? || DEFAULTS[:env]) as String
      @host        = (ENV["GUFF_HOST"]? || DEFAULTS[:host]) as String
      @port        = (ENV["GUFF_PORT"]? || DEFAULTS[:port]) as String
      @data_dir    = (ENV["GUFF_DATA_DIR"]? || DEFAULTS[:data_dir]) as String
      @assets_dir  = (ENV["GUFF_ASSETS_DIR"]? || DEFAULTS[:assets_dir]) as String
    end

    VALID_MODES = %w{init run help}

    def mode=(mode : String)
      raise "unknown mode: \"#{mode}\"" unless VALID_MODES.includes?(mode)
      @mode = mode
    end

    VALID_ENVS = %w{development production}

    def env=(env : String)
      raise "unknown environment: \"#{env}\"" unless VALID_ENVS.includes?(env)
      @env = env
    end

    def port=(port : String)
      val = port.to_i
      raise "invalid port: #{port}" unless val > 0 && val < 65535
      @port = port
    end

    def assets_dir=(dir : String)
      raise "missing assets dir: \"#{dir}\"" unless Dir.exists?(dir)
      @assets_dir = dir
    end

    def self.parse(
      app   : String,
      args  : Array(String)
    ) : Config
      r = Config.new

      raise "missing mode" unless args.size > 0

      # get mode
      r.mode = case mode = args.shift
      when "-h", "--help"
        "help"
      else
        mode
      end

      # parse arguments
      p = OptionParser.parse(args) do |p|
        p.banner = "Usage: #{app} [mode] <args>"

        p.separator
        p.separator("Run Options:")

        p.on(
          "-H HOST", "--host HOST",
          "TCP host (defaults to \"#{DEFAULTS[:host]}\")"
        ) do |arg|
          r.host = arg
        end

        p.on(
          "-p PORT", "--port PORT",
          "TCP port (defaults to \"#{DEFAULTS[:port]}\")"
        ) do |arg|
          r.port = arg
        end

        p.separator
        p.separator("Directory Options:")

        p.on(
          "-D DIR", "--data-dir DIR",
          "Data directory (defaults to \"#{DEFAULTS[:data_dir]}\")"
        ) do |arg|
          r.data_dir = arg
        end

        p.on(
          "-A DIR", "--assets-dir DIR",
          "Guff assets directory (defaults to \"#{DEFAULTS[:assets_dir]}\")"
        ) do |arg|
          r.assets_dir = arg
        end

        p.separator
        p.separator("Development Options:")

        p.on(
          "-E ENV", "--environment ENV",
          "Environment (defaults to \"#{DEFAULTS[:env]})\""
        ) do |arg|
          r.env = arg
        end

        p.separator
        p.separator("Other Options:")

        p.on("-h", "--help", "Print usage.") do
          r.mode = "help"
        end
      end

      case r.mode
      when "init"
        # shortcut for -D parameter
        r.data_dir = args.shift if args.size > 0
      when "help"
        # print help
        puts p
      end

      # return config
      r
    end
  end

  module MimeType
    TYPES = {
      ".js":    "text/javascript; charset=utf-8",
      ".css":   "text/css; charset=utf-8",
      ".html":  "text/html; charset=utf-8",
      ".png":   "image/png",
      ".jpeg":  "image/jpeg",
      ".jpg":   "image/jpeg",
      ".otf":   "application/vnd.ms-opentype",
      ".eot":   "application/vnd.ms-fontobject",
      ".svg":   "image/svg+xml",
      ".ttf":   "application/x-font-ttf",
      ".woff":  "application/font-woff",
      ".woff2": "application/font-woff",
    }

    def self.from_path(path : String) : String
      TYPES[File.extname(path)]? || "application/octet-stream"
    end
  end

  class Context
    property :config #, :models

    def initialize(@config : Config)
      # @models = nil
    end
  end

  module Views
    abstract class View
      def initialize(@context : Context)
      end

      def h(s : String) : String
        HTML.escape(s)
      end

      TEMPLATES = {
        :script => "<script type='text/javascript' src='%s'></script>",
        :style  => "<link rel='stylesheet' type='text/css' href='%s'/>",
      }

      private def assets(key : Symbol, paths : Array(String))
        paths.map { |path| TEMPLATES[key] % [h(path)] }.join
      end

      def scripts(paths : Array(String))
        assets(:script, paths)
      end

      def styles(paths : Array(String))
        assets(:style, paths)
      end
    end

    class AdminPageView < View
      ECR.def_to_s("src/views/admin-page.ecr")
    end

    class LoginPageView < View
      ECR.def_to_s("src/views/login-page.ecr")
    end
  end

  module Handlers
    abstract class Handler < HTTP::Handler
      def initialize(@context : Context)
        super()
      end
    end

    abstract class AuthenticatedHandler < Handler
      def initialize(context : Context, roles : Array(String))
        super(context)
        @roles = roles
      end

      def call(context : HTTP::Server::Context)
        role = context.request.headers["x-guff-role"]?

        if role && @roles.includes?(role)
          authenticated_call(context)
        else
          call_next(context)
        end
      end

      abstract def authenticated_call(context : HTTP::Server::Context)
    end

    class SessionHandler < Guff::Handlers::Handler
      def call(context : HTTP::Server::Context)
        if @context.config.env == "development"
          # TODO: add handler support
          context.request.headers["x-guff-user-id"] = "0"
          context.request.headers["x-guff-role"] = "admin"
        else
          context.request.headers["x-guff-user-id"] = ""
          context.request.headers["x-guff-role"] = ""
        end

        call_next(context)
      end
    end

    class AssetsHandler < AuthenticatedHandler
      def initialize(context : Context)
        super(context, %w{admin editor})
        @etags = {} of String => String
      end

      def authenticated_call(context : HTTP::Server::Context)
        req_path = context.request.path.not_nil!

        if matching_request?(context.request.method, req_path)
          # get expanded path to file
          if abs_path = expand_path(req_path)
            # get file digest
            etag = get_file_etag(abs_path)

            # check for cache header
            if context.request.headers["if-none-match"]? == etag
              # cached, send 304 not modified
              context.response.status_code = 304
            else
              # not cached, set code and send headers
              context.response.status_code = 200
              context.response.content_type = MimeType.from_path(abs_path)
              context.response.content_length = File.size(abs_path)
              context.response.headers["etag"] = etag

              if context.request.method == "GET"
                # send body for GET requests
                File.open(abs_path) do |fh|
                  IO.copy(fh, context.response)
                end
              end
            end
          else
            # expanded path does not exist
            call_next(context)
          end
        else
          # not a matching request
          call_next(context)
        end
      end

      VALID_METHODS = %w{GET HEAD}
      PATH_RE = %r{^/guff/assets/}

      private def matching_request?(method, path)
        VALID_METHODS.includes?(method) && PATH_RE.match(path)
      end

      private def expand_path(req_path : String) : String?
        # unescape path, check for nil byte
        path = URI.unescape(req_path)
        return nil if path.includes?('\0')

        # build absolute path
        r = File.join(
          @context.config.assets_dir,
          File.expand_path(path.gsub(PATH_RE, ""), "/")
        )

        # return path if file exists, or nil otherwise
        File.file?(r) ? r : nil
      end

      private def get_file_etag(path : String) : String
        # FIXME: rather than a hash this should be an HMAC
        @etags[path] ||= OpenSSL::Digest.new("SHA1").file(path).hexdigest
      end
    end

    class AdminPageHandler < AuthenticatedHandler
      def initialize(context : Context)
        super(context, %w{admin editor})
      end

      PATH_RE = %r{^/guff/admin/$}

      def authenticated_call(context : HTTP::Server::Context)
        if context.request.path.not_nil!.match(PATH_RE)
          context.response.content_type = "text/html; charset=utf-8"
          context.response.status_code = 200
          Views::AdminPageView.new(@context).to_s(context.response.output)
        else
          call_next(context)
        end
      end
    end

    class LoginPageHandler < Handler
      PATH_RE = %r{^/guff/login/$}
      VALID_METHODS = %w{GET HEAD}

      def call(context : HTTP::Server::Context)
        if VALID_METHODS.includes?(context.request.method) &&
           PATH_RE.match(context.request.path.not_nil!)
          case context.request.method
          when "GET"
            context.response.content_type = "text/html; charset=utf-8"
            context.response.status_code = 200
            Views::LoginPageView.new(@context).to_s(context.response.output)
          when "POST"
            # TODO: try login
          else
            raise "invalid HTTP method"
          end
        else
          call_next(context)
        end
      end
    end

    HANDLERS = [{
      dev:  true,
      id:   :error,
    }, {
      dev:  false,
      id:   :log,
    }, {
      dev:  false,
      id:   :deflate,
    }, {
      dev:  false,
      id:   :session,
    }, {
      dev:  false,
      id:   :assets,
    }, {
      dev:  false,
      id:   :admin,
    }, {
      dev:  false,
      id:   :login,
    }]

    def self.get(context : Context) : Array(HTTP::Handler)
      is_dev = (context.config.env == "development")
      
      HANDLERS.select { |row|
        !(row[:dev] as Bool) || is_dev
      }.map { |row|
        make_handler(row[:id] as Symbol, context)
      }
    end

    def self.make_handler(
      handler_id : Symbol,
      context : Context
    ) : HTTP::Handler
      case handler_id
      when :error
        HTTP::ErrorHandler.new
      when :log
        HTTP::LogHandler.new
      when :deflate
        HTTP::DeflateHandler.new
      when :session
        SessionHandler.new(context)
      when :assets
        AssetsHandler.new(context)
      when :admin
        AdminPageHandler.new(context)
      when :login
        LoginPageHandler.new(context)
      else
        raise "unknown handler id: #{handler_id}"
      end
    end
  end

  module CLI
    module Actions
      abstract class Action
        def self.run(config : Config)
          new(config).run
        end

        def initialize(@config : Config)
        end

        abstract def run
      end

      class InitAction < Action
        def run
          STDERR.puts "TODO: building directory"
        end
      end

      class RunAction < Action
        def run
          STDERR.puts "TODO: running web server"
          check_dirs

          # create context
          context = Context.new(@config)

          STDERR.puts "listening on %s:%s" % [@config.host, @config.port]

          # run server
          HTTP::Server.new(
            @config.host,
            @config.port.to_i,
            Handlers.get(context)
          ).listen
        end

        private def check_dirs
          {
            "assets": @config.assets_dir,
            "data":   @config.data_dir,
          }.each do |name, dir|
            unless Dir.exists?(dir)
              raise "missing #{name} directory: \"#{dir}\""
            end
          end
        end
      end
    end

    def self.run(app : String, args : Array(String))
      begin
        begin
          config = Config.parse(app, args)
        rescue err
          raise "#{err}.  Use --help for usage"
        end

        case config.mode
        when "init"
          Actions::InitAction.run(config)
        when "run"
          Actions::RunAction.run(config)
        when "help"
          # do nothing
        else
          # never reached
          raise "unknown mode: #{config.mode}"
        end
      rescue err
        STDERR.puts "ERROR: #{err}."
        exit -1
      end
    end
  end
end

Guff::CLI.run($0, ARGV)