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

private macro define_model_set_getters(hash)
  {% for name, klass in hash %}
    def {{ name.id }} : {{ klass.id }}
      (@cache[{{ name }}] ||= {{ klass.id }}.new(@context)) as {{ klass.id }}
    end
  {% end %}
end

private macro include_api_modules(modules)
  {% for mod in modules.resolve %}
    include {{ mod.id }}
  {% end %}
end

private macro api_method_dispatch(modules)
  case namespace
  {% for mod in modules.resolve %}
    {% mod_name = mod.resolve.name.gsub(/^.*:(.*)API$/, "\\1").downcase %}
    when {{ mod_name.stringify }}
    case method
    {% for mod_method in mod.resolve.methods %}
      {% method_name = mod_method.name.gsub(/^do_([^_]+)_/, "") %}
      when {{ method_name.stringify }}
        {{ mod_method.name.id }}(params)
    {% end %}
    else
      raise "unknown method: #{namespace}/#{method}"
    end
  {% end %}
  else
    raise "unknown namespace: #{namespace}"
  end
end

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

    DEFAULTS = {
      mode:       "help",
      env:        "production",
      host:       "127.0.0.1",
      port:       "8989",
      data_dir:   "./data",
      system_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
      @system_dir  = (ENV["GUFF_SYSTEM_DIR"]? || DEFAULTS[:system_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 system_dir=(dir : String)
      raise "missing system dir: \"#{dir}\"" unless Dir.exists?(dir)
      @system_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(
          "-S DIR", "--system-dir DIR",
          "Guff system directory (defaults to \"#{DEFAULTS[:system_dir]}\")"
        ) do |arg|
          r.system_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

  module Models
    abstract class Model
      def initialize(@context : Context)
      end
    end

    class UserModel < Model
      def login(user : String, pass : String) : String?
        if @context.development?
          if user == "test" && pass == "test"
            "0"
          else
            nil
          end
        else
          # TODO: handle login
          nil
        end
      end

      def has_role?(user_id : String?, roles : Array(String))
        raise "empty role list" unless roles.size > 0

        if user_id && user_id.size > 0
          if @context.development?
            user_id == "0"
          else
            # TODO: add role query
          end
        else
          # empty user id
          false
        end
      end

      def add_user(
        name      : String?         = nil,
        email     : String?         = nil,
        password  : String?         = nil,
        groups    : Array(String)?  = nil,
        active    : Bool?           = nil,
      ) : Int64
        # TODO create user
        user_id = 0_i64

        # set user attributes
        set_user(
          user_id:  user_id,
          email:    email,
          password: password,
          groups:   groups,
          active:   active,
        )

        # return user id
        user_id
      end

      def set_user(
        user_id   : Int64,
        name      : String?         = nil,
        email     : String?         = nil,
        password  : String?         = nil,
        groups    : Array(String)?  = nil,
        active    : Bool?           = nil,
      )
      end

      def get_users
      end
    end

    class SessionModel < Model
      def initialize(context : Context)
        super(context)
        @sessions = {} of String => String
      end

      def load(id : String) : String?
        @sessions[id]?
      end

      def save(id : String, data : String)
        if @sessions.has_key?(id)
          @sessions[id] = data
          true
        else
          false
        end
      end

      def delete(id : String?)
        @sessions.delete(id) if id
        false
      end

      def create(data : String) : String
        # generate id
        r = SecureRandom.hex(32)

        # save session
        @sessions[r] = data

        # return session id
        r
      end
    end

    class CSRFModel < Model
      getter :minutes

      def initialize(context : Context)
        super(context)
        @cache = {} of String => Int64

        # expire form after 5 minutes
        # TODO: make this configurable
        @minutes = 5
      end

      def create_token
        remove_expired_tokens

        # generate and cache new token
        r = SecureRandom.hex(16)
        @cache[r] = Time.now.epoch + 60 * @minutes

        # return token
        r
      end

      def use_token(id : String)
        remove_expired_tokens

        if @cache.has_key?(id)
          # remove token, return success
          @cache.delete(id)
          true
        else
          # return failure
          false
        end
      end

      private def remove_expired_tokens
        now = Time.now.epoch

        # FIXME: limit the size of the cache
        # to prevent insane memory use

        # remove expired entries
        @cache.delete_if do |key, val|
          val < now
        end
      end
    end
  end

  class ModelSet
    def initialize(@context : Context)
      @cache = {} of Symbol => Models::Model
    end

    define_model_set_getters({
      user:     Models::UserModel,
      session:  Models::SessionModel,
      csrf:     Models::CSRFModel,
    })
  end

  class Session < Hash(String, String)
    getter :session_id

    # session cookie name
    # FIXME: does this belong here?
    COOKIE = "guff_session"

    def initialize(@context : Context)
      super()
      @session_id = nil
    end

    def load(id : String)
      begin
        # clear existing session
        clear

        # load session values
        JSON.parse(@context.models.session.load(id).not_nil!).each do |key, val|
          self[key.as_s] = val.as_s
        end

        # save session id
        @session_id = id

        # return success
        true
      rescue err
        STDERR.puts "session load failed: #{err}"
        # invalid session id, return failure
        false
      end
    end

    def create(hash : Hash(String, String)) : String
      clear
      merge!(hash)
      @session_id = @context.models.session.create(hash.to_json)
    end

    def save
      if valid?
        @context.models.session.save(@session_id, to_json)

        # return success
        true
      else
        # no session, return failure
        false
      end
    end

    def clear
      super
      @session_id = nil
    end

    def delete : String?
      r = @session_id

      if valid?
        @context.models.session.delete(r)
        clear
      end

      r
    end

    def valid?
      @session_id != nil
    end
  end

  class Context
    getter :config

    def initialize(@config : Config)
    end

    def models
      @models ||= ModelSet.new(self)
    end

    def session
      @session ||= Session.new(self)
    end

    def user_id
      session["user_id"]?
    end

    def has_role?(roles : Array(String))
      models.user.has_role?(user_id, roles)
    end

    def development?
      @is_development ||= (@config.env == "development") as Bool
    end
  end

  module APIs
    module PostAPI
      def do_post_get_posts(params : HTTP::Params)
        { "asdf": "foo" }
      end
    end

    module UserAPI
      def do_user_add_user(params : HTTP::Params)
        user_id = @context.models.user.add_user(
          name:     params["name"]?,
          email:    params["email"],
          password: params["password"]?,
          active:   params["active"]? ? (params["active"] == "t") : nil,
          # groups:   params["groups"]? ? JSON.parse(params["groups"]) : nil,
        )

        { "user_id": user_id }
      end
    end
  end

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

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

    class TabView < View
      def initialize(
        context : Context,
        @prefix : String,
        @tab : Hash(Symbol, String)
      )
        super(context)
        @id = h("%s-tab-%s" % [@prefix, @tab[:id]]) as String
        @target = h("%s-pane-%s" % [@prefix, @tab[:id]]) as String
      end

      private def v(id : Symbol) : String
        raise "unknown id: #{id}" unless @tab.has_key?(id)
        h(@tab[id])
      end

      ECR.def_to_s("src/views/tab.ecr")
    end

    abstract class HTMLView < View
      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))
        String.build do |io|
          paths.each do |path|
            io << TEMPLATES[key] % [h(path)]
          end
        end
      end

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

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

      def tabs(rows : Array(Hash(Symbol, String)))
        String.build do |io|
          rows.each do |row|
            TabView.new(@context, "admin", row).to_s(io)
          end
        end
      end
    end

    class AdminPageView < HTMLView
      TITLE = "Guff Admin"

      TABS = [{
        id:   "home",
        css:  "active",
        icon: "fa-home",
        name: "Home",
        text: "View home tab.",
      }, {
        id:   "posts",
        css:  "",
        icon: "fa-cubes",
        name: "Posts",
        text: "Manage blog, pages, and projects.",
      }, {
        id:   "files",
        css:  "",
        icon: "fa-files-o",
        name: "Files",
        text: "Manage files.",
      }, {
        id:   "users",
        css:  "",
        icon: "fa-users",
        name: "Users",
        text: "Manage users and permissions.",
      }, {
        id:   "settings",
        css:  "",
        icon: "fa-cog",
        name: "Settings",
        text: "Configure site settings.",
      }]

      def tabs
        super(TABS)
      end

      ECR.def_to_s("src/views/admin-page.ecr")
    end

    class LoginPageView < HTMLView
      def initialize(context : Context, @error : String? = nil)
        super(context)
      end

      def get_csrf_token
        @context.models.csrf.create_token
      end

      ECR.def_to_s("src/views/login-page.ecr")
    end

    class LogoutPageView < HTMLView
      ECR.def_to_s("src/views/logout-page.ecr")
    end
  end

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

      protected def valid_origin_headers?(headers : HTTP::Headers)
        # FIXME: need to compare these against something rather than
        # just making sure that they are there
        %w{origin referer}.any? do |key|
          headers[key]? && headers[key].size > 0
        end
      end
    end

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

      def call(context : HTTP::Server::Context)
        if @context.has_role?(@roles)
          authenticated_call(context)
        else
          call_next(context)
        end
      end

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

    class SessionHandler < Handler
      def call(context : HTTP::Server::Context)
        # clear session
        @context.session.clear

        if cookie = context.request.cookies[Guff::Session::COOKIE]?
          # load session
          @context.session.load(cookie.value)
        end

        call_next(context)
      end
    end

    class APIHandler < Handler
      PATH_RE = %r{^/guff/api/(?<namespace>[\w_-]+)/(?<method>[\w_-]+)$}

      API_MODULES = [
        APIs::PostAPI,
        APIs::UserAPI,
      ]

      include_api_modules(API_MODULES)

      def call(context : HTTP::Server::Context)
        if context.request.method == "POST" ||
           (@context.development? && context.request.method == "GET")
          if md = PATH_RE.match(context.request.path.not_nil!)
            namespace, method = %w{namespace method}.map { |k| md[k] }
            params = HTTP::Params.parse(context.request.body || "")

            code, data = begin
              { 200, api_method_dispatch(API_MODULES) }
            rescue err
              STDERR.puts "ERROR: #{err}"
              { 400, { "error": err.to_s } }
            end

            # send json response
            context.response.status_code = code
            context.response.content_type = "application/json; charset=utf-8"
            data.to_json(context.response)
          else
            call_next(context)
          end
        else
          call_next(context)
        end
      end
    end

    class AssetsHandler < Handler
      def initialize(context : Context)
        super(context)
        @etags = {} of String => String
      end

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

        if matching_request?(context.request.method, req_path) &&
           valid_origin_headers?(context.request.headers)
          # 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.headers["x-frame-options"] = "SAMEORIGIN"
              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.system_dir,
          "assets",
          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.html$}

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

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

      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"
            reply(context.response)
          when "POST"
            begin
              # check for valid origin or referer header
              unless valid_origin_headers?(context.request.headers)
                raise "missing origin and referer headers"
              end

              # create session
              session_id = @context.session.create({
                "user_id": login(context.request.body),
              })

              # add cookie
              context.response.cookies << HTTP::Cookie.new(
                name:       Guff::Session::COOKIE,
                value:      session_id as String,
                http_only:  true,

                # TODO
                # expires:
                # secure:
              )

              # redirect to admin panel
              context.response.headers["location"] = "/guff/admin.html"
              context.response.status_code = 302
            rescue err
              # log error
              STDERR.puts "login failed: #{err}"
              reply(context.response, "invalid login")
            end
          else
            raise "invalid HTTP method"
          end
        else
          call_next(context)
        end
      end

      private def reply(
        response : HTTP::Server::Response,
        error : String? = nil
      )
        response.headers["x-frame-options"] = "SAMEORIGIN"
        response.content_type = "text/html; charset=utf-8"
        response.status_code = 200
        Views::LoginPageView.new(@context, error).to_s(response)
      end

      private def login(body : String?) : String
        # check body
        raise "empty request body" if body.nil? || body.size == 0

        # parse request parameters
        params = HTTP::Params.parse(body.not_nil!)

        # check login parameters
        raise "missing login parameters" unless %w{
          username
          password
          csrf_token
        }.all? do |key|
          params.has_key?(key) && params[key].size > 0
        end

        # check csrf token
        unless @context.models.csrf.use_token(params["csrf_token"])
          raise "invalid csrf token"
        end

        # try login
        user_id =  @context.models.user.login(
          params["username"],
          params["password"]
        )

        # check user id
        raise "invalid credentials" unless user_id

        # return user id
        user_id
      end
    end

    class LogoutPageHandler < Handler
      PATH_RE = %r{^/guff/logout.html$}

      def call(context : HTTP::Server::Context)
        if context.request.method == "GET" &&
           PATH_RE.match(context.request.path.not_nil!) &&
           valid_origin_headers?(context.request.headers)
          # delete session
          @context.session.delete

          # clear cookie
          context.response.cookies << HTTP::Cookie.new(
            name:       Guff::Session::COOKIE,
            value:      "",
            expires:    Time.epoch(0),
            http_only:  true,
          )

          # build remaining headers
          context.response.headers["x-frame-options"] = "SAMEORIGIN"
          context.response.content_type = "text/html; charset=utf-8"
          context.response.status_code = 200

          # draw page
          Views::LogoutPageView.new(@context).to_s(context.response)
        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:   :api,
    }, {
      dev:  false,
      id:   :assets,
    }, {
      dev:  false,
      id:   :admin,
    }, {
      dev:  false,
      id:   :login,
    }, {
      dev:  false,
      id:   :logout,
    }]

    def self.get(context : Context) : Array(HTTP::Handler)
      HANDLERS.select { |row|
        !(row[:dev] as Bool) || context.development?
      }.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 :api
        APIHandler.new(context)
      when :assets
        AssetsHandler.new(context)
      when :admin
        AdminPageHandler.new(context)
      when :login
        LoginPageHandler.new(context)
      when :logout
        LogoutPageHandler.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
          {
            "system": @config.system_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
          # parse command-line arguments
          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)