require 'strscan'
require 'jsduck/meta_tag_registry'

module JsDuck

  # Parses doc-comment into array of @tags
  #
  # For each @tag it produces Hash like the following:
  #
  #     {
  #       :tagname => :cfg/:property/:type/:extends/...,
  #       :doc => "Some documentation for this tag",
  #       ...@tag specific stuff like :name, :type, and so on...
  #     }
  #
  # When doc-comment begins with comment, not preceded by @tag, then
  # the comment will be placed into Hash with :tagname => :default.
  #
  # Unrecognized @tags are left as is into documentation as if they
  # were normal text.
  #
  # @see and {@link} are parsed separately in JsDuck::DocFormatter.
  #
  class DocParser
    def initialize
      @ident_pattern = /[$\w-]+/
      @ident_chain_pattern = /[$\w-]+(\.[$\w-]+)*/
      @meta_tags = MetaTagRegistry.instance
    end

    def parse(input)
      @tags = []
      @input = StringScanner.new(purify(input))
      parse_loop
      # The parsing process can leave whitespace at the ends of
      # doc-strings, here we get rid of it.  Additionally null all empty docs
      @tags.each do |tag|
        tag[:doc].strip!
        tag[:doc] = nil if tag[:doc] == ""
      end
      # Get rid of empty default tag
      if @tags.first && @tags.first[:tagname] == :default && !@tags.first[:doc]
        @tags.shift
      end
      @tags
    end

    # Extracts content inside /** ... */
    def purify(input)
      result = []
      # We can have two types of lines:
      # - those beginning with *
      # - and those without it
      indent = nil
      input.each_line do |line|
        line.chomp!
        if line =~ /\A\s*\*\s?(.*)\Z/
          # When comment contains *-lines, switch indent-trimming off
          indent = 0
          result << $1
        elsif line =~ /\A\s*\Z/
          # pass-through empty lines
          result << line
        elsif indent == nil && line =~ /\A(\s*)(.*?\Z)/
          # When indent not measured, measure it and remember
          indent = $1.length
          result << $2
        else
          # Trim away indent if available
          result << line.sub(/\A\s{0,#{indent||0}}/, "")
        end
      end
      return result.join("\n")
    end

    def add_tag(tag)
      @tags << @current_tag = {:tagname => tag, :doc => ""}
    end

    def parse_loop
      add_tag(:default)
      while !@input.eos? do
        if look(/@class\b/)
          at_class
        elsif look(/@extends?\b/)
          at_extends
        elsif look(/@mixins?\b/)
          class_list_at_tag(/@mixins?/, :mixins)
        elsif look(/@alternateClassNames?\b/)
          class_list_at_tag(/@alternateClassNames?/, :alternateClassNames)
        elsif look(/@uses\b/)
          class_list_at_tag(/@uses/, :uses)
        elsif look(/@requires\b/)
          class_list_at_tag(/@requires/, :requires)
        elsif look(/@singleton\b/)
          boolean_at_tag(/@singleton/, :singleton)
        elsif look(/@event\b/)
          at_event
        elsif look(/@method\b/)
          at_method
        elsif look(/@constructor\b/)
          boolean_at_tag(/@constructor/, :constructor)
        elsif look(/@param\b/)
          at_param
        elsif look(/@returns?\b/)
          at_return
        elsif look(/@cfg\b/)
          at_cfg
        elsif look(/@property\b/)
          at_property
        elsif look(/@type\b/)
          at_type
        elsif look(/@xtype\b/)
          at_xtype(/@xtype/, "widget")
        elsif look(/@ftype\b/)
          at_xtype(/@ftype/, "feature")
        elsif look(/@ptype\b/)
          at_xtype(/@ptype/, "plugin")
        elsif look(/@member\b/)
          at_member
        elsif look(/@inherit[dD]oc\b/)
          at_inheritdoc
        elsif look(/@alias\s+([\w.]+)?#\w+/)
          # For backwards compatibility.
          # @alias tag was used as @inheritdoc before
          at_inheritdoc
        elsif look(/@alias/)
          at_alias
        elsif look(/@var\b/)
          at_var
        elsif look(/@throws\b/)
          at_throws
        elsif look(/@enum\b/)
          at_enum
        elsif look(/@override\b/)
          at_override
        elsif look(/@inheritable\b/)
          boolean_at_tag(/@inheritable/, :inheritable)
        elsif look(/@accessor\b/)
          boolean_at_tag(/@accessor/, :accessor)
        elsif look(/@evented\b/)
          boolean_at_tag(/@evented/, :evented)
        elsif look(/@/)
          match(/@/)
          tag = @meta_tags[look(/\w+/)]
          if tag
            meta_at_tag(tag)
          else
            @current_tag[:doc] += "@"
          end
        elsif look(/[^@]/)
          @current_tag[:doc] += match(/[^@]+/)
        end
      end
    end

    # Matches the given meta-tag
    def meta_at_tag(tag)
      prev_tag = @current_tag

      add_tag(:meta)
      @current_tag[:name] = tag.key
      match(/\w+/)
      skip_horiz_white

      if tag.boolean
        # For boolean tags, only scan the tag name and switch context
        # back to previous tag.
        skip_white
        @current_tag = prev_tag
      elsif tag.multiline
        # For multiline tags we leave the tag open for :doc addition
        # just like with built-in multiline tags.
      else
        # Fors singleline tags, scan to the end of line and finish the
        # tag.
        @current_tag[:doc] = match(/.*$/).strip
        skip_white
        @current_tag = prev_tag
      end
    end

    # matches @class name ...
    def at_class
      match(/@class/)
      add_tag(:class)
      maybe_ident_chain(:name)
      skip_white
    end

    # matches @extends name ...
    def at_extends
      match(/@extends?/)
      add_tag(:extends)
      maybe_ident_chain(:extends)
      skip_white
    end

    # matches @<tagname> classname1 classname2 ...
    def class_list_at_tag(regex, tagname)
      match(regex)
      add_tag(tagname)
      skip_horiz_white
      @current_tag[tagname] = class_list
      skip_white
    end

    # matches @event name ...
    def at_event
      match(/@event/)
      add_tag(:event)
      maybe_name
      skip_white
    end

    # matches @method name ...
    def at_method
      match(/@method/)
      add_tag(:method)
      maybe_name
      skip_white
    end

    # matches @param {type} [name] (optional) ...
    def at_param
      match(/@param/)
      add_tag(:param)
      maybe_type
      maybe_name_with_default
      maybe_optional
      skip_white
    end

    # matches @return {type} [ return.name ] ...
    def at_return
      match(/@returns?/)
      add_tag(:return)
      maybe_type
      skip_white
      if look(/return\.\w/)
        @current_tag[:name] = ident_chain
      else
        @current_tag[:name] = "return"
      end
      skip_white
    end

    # matches @cfg {type} name ...
    def at_cfg
      match(/@cfg/)
      add_tag(:cfg)
      maybe_type
      maybe_name_with_default
      maybe_required
      skip_white
    end

    # matches @property {type} name ...
    #
    # ext-doc doesn't support {type} and name for @property - name is
    # inferred from source and @type is required to specify type,
    # jsdoc-toolkit on the other hand follows the sensible route, and
    # so do we.
    def at_property
      match(/@property/)
      add_tag(:property)
      maybe_type
      maybe_name_with_default
      skip_white
    end

    # matches @var {type} $name ...
    def at_var
      match(/@var/)
      add_tag(:css_var)
      maybe_type
      maybe_name_with_default
      skip_white
    end

    # matches @throws {type} ...
    def at_throws
      match(/@throws/)
      add_tag(:throws)
      maybe_type
      skip_white
    end

    # matches @enum {type} name ...
    def at_enum
      match(/@enum/)
      add_tag(:class)
      @current_tag[:enum] = true
      maybe_type
      maybe_name_with_default
      skip_white
    end

    # matches @override name ...
    def at_override
      match(/@override/)
      add_tag(:override)
      maybe_ident_chain(:class)
      skip_white
    end

    # matches @type {type}  or  @type type
    #
    # The presence of @type implies that we are dealing with property.
    # ext-doc allows type name to be either inside curly braces or
    # without them at all.
    def at_type
      match(/@type/)
      add_tag(:type)
      skip_horiz_white
      if look(/\{/)
        tdf = typedef
        @current_tag[:type] = tdf[:type]
        @current_tag[:optional] = true if tdf[:optional]
      elsif look(/\S/)
        @current_tag[:type] = match(/\S+/)
      end
      skip_white
    end

    # matches @member name ...
    def at_member
      match(/@member/)
      add_tag(:member)
      maybe_ident_chain(:member)
      skip_white
    end

    # matches @xtype/ptype/ftype/... name
    def at_xtype(tag, namespace)
      match(tag)
      add_tag(:alias)
      skip_horiz_white
      @current_tag[:name] = namespace + "." + (ident_chain || "")
      skip_white
    end

    # matches @alias <ident-chain>
    def at_alias
      match(/@alias/)
      add_tag(:alias)
      skip_horiz_white
      @current_tag[:name] = ident_chain
      skip_white
    end

    # matches @inheritdoc class.name#static-type-member
    def at_inheritdoc
      match(/@inherit[dD]oc|@alias/)

      add_tag(:inheritdoc)
      skip_horiz_white

      if look(@ident_chain_pattern)
        @current_tag[:cls] = ident_chain
      end

      if look(/#\w/)
        match(/#/)
        if look(/static-/)
          @current_tag[:static] = true
          match(/static-/)
        end
        if look(/(cfg|property|method|event|css_var|css_mixin)-/)
          @current_tag[:type] = ident.to_sym
          match(/-/)
        end
        @current_tag[:member] = ident
      end

      skip_white
    end

    # Used to match @private, @ignore, @hide, ...
    def boolean_at_tag(regex, propname)
      match(regex)
      add_tag(propname)
      skip_white
    end

    # matches {type} if possible and sets it on @current_tag
    # Also checks for {optionality=} in type definition.
    def maybe_type
      skip_horiz_white
      if look(/\{/)
        tdf = typedef
        @current_tag[:type] = tdf[:type]
        @current_tag[:optional] = true if tdf[:optional]
      end
    end

    # matches: <ident-chain> | "[" <ident-chain> [ "=" <default-value> ] "]"
    def maybe_name_with_default
      skip_horiz_white
      if look(/\[/)
        match(/\[/)
        maybe_ident_chain(:name)
        skip_horiz_white
        if look(/=/)
          match(/=/)
          skip_horiz_white
          @current_tag[:default] = default_value
        end
        skip_horiz_white
        match(/\]/)
        @current_tag[:optional] = true
      else
        maybe_ident_chain(:name)
      end
    end

    # matches: "(optional)"
    def maybe_optional
      skip_horiz_white
      if look(/\(optional\)/i)
        match(/\(optional\)/i)
        @current_tag[:optional] = true
      end
    end

    # matches: "(required)"
    def maybe_required
      skip_horiz_white
      if look(/\(required\)/i)
        match(/\(required\)/i)
        @current_tag[:optional] = false
      end
    end

    # matches identifier name if possible and sets it on @current_tag
    def maybe_name
      skip_horiz_white
      if look(@ident_pattern)
        @current_tag[:name] = match(@ident_pattern)
      end
    end

    # matches ident.chain if possible and sets it on @current_tag
    def maybe_ident_chain(propname)
      skip_horiz_white
      if look(@ident_chain_pattern)
        @current_tag[propname] = ident_chain
      end
    end

    # Attempts to allow balanced braces in default value.
    # When the nested parsing doesn't finish at closing "]",
    # roll back to beginning and simply grab anything up to closing "]".
    def default_value
      start_pos = @input.pos
      value = parse_balanced(/\[/, /\]/, /[^\[\]]*/)
      if look(/\]/)
        value
      else
        @input.pos = start_pos
        match(/[^\]]*/)
      end
    end

    # matches {...=} and returns text inside brackets
    def typedef
      match(/\{/)

      name = parse_balanced(/\{/, /\}/, /[^{}]*/)

      if name =~ /=$/
        name = name.chop
        optional = true
      else
        optional = nil
      end

      match(/\}/)

      return {:type => name, :optional => optional}
    end

    # Helper method to parse a string up to a closing brace,
    # balancing opening-closing braces in between.
    #
    # @param re_open  The beginning brace regex
    # @param re_close The closing brace regex
    # @param re_rest  Regex to match text without any braces
    def parse_balanced(re_open, re_close, re_rest)
      result = match(re_rest)
      while look(re_open)
        result += match(re_open)
        result += parse_balanced(re_open, re_close, re_rest)
        result += match(re_close)
        result += match(re_rest)
      end
      result
    end

    # matches <ident_chain> <ident_chain> ... until line end
    def class_list
      skip_horiz_white
      classes = []
      while look(@ident_chain_pattern)
        classes << ident_chain
        skip_horiz_white
      end
      classes
    end

    # matches chained.identifier.name and returns it
    def ident_chain
      @input.scan(@ident_chain_pattern)
    end

    # matches identifier and returns its name
    def ident
      @input.scan(/\w+/)
    end

    def look(re)
      @input.check(re)
    end

    def match(re)
      @input.scan(re)
    end

    def skip_white
      @input.scan(/\s+/)
    end

    # skips horizontal whitespace (tabs and spaces)
    def skip_horiz_white
      @input.scan(/[ \t]+/)
    end
  end

end