#!/usr/bin/env ruby
#
# Copyright(C) Simon Howard
#
# Permission is hereby granted, free of charge, to any person obtaining a
# copy of this software and associated documentation files (the "Software"),
# to deal in the Software without restriction, including without limitation
# the rights to use, copy, modify, merge, publish, distribute, sublicense,
# and/or sell copies of the Software, and to permit persons to whom the
# Software is furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
# THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
# FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
# DEALINGS IN THE SOFTWARE.
#
#
# Script to generate history ChangeLog from a git repository, in a format
# almost identical to my svnhistory script.
#

class Change
    attr_accessor :author, :time, :description

    def initialize(change_date)
        @time = change_date.sub(/ \+.*/, "")
        @author = "???"
        @description = ""
    end

    # Combine multiple lines of text into long run-on lines.  Empty
    # lines of text denote paragraphs.  Lines beginning with '*'
    # are also recognised as bullet point lists.

    def combine_lines(input)
        result = ""

        input.each_line do |s|
            s = s.chomp

            if result.length > 0 && result[-1, 1] != "\n"

                # Don't do any of this if we just started a new line

                if s =~ /^\s*$/
                    # empty line; make this break a paragraph.
                    result += "\n\n"
                elsif s =~ /^\s*\*/
                    # bullet point
                    result += "\n"
                else
                    result += " "
                end
            end

            result += s
        end

        result
    end

    # Reformat the description and break into lines

    def break_lines(input)
        result = ""

        input.each_line do |s|

            if s =~ /^\s*$/
                # empty line
                result += "\n"
            else

                # Amount to indent each line by so that they align
                # with the initial bullet point (if this line is a
                # bullet point)

                indent_length = if s =~ /^(\s*\*\s*)/
                                    $1.length
                                else
                                    0
                                end

                # Split this line into words, then add them to nextline
                # one at a time until it reaches a 70 character limit.

                nextline = s[0, indent_length]
                s = s[indent_length, s.length]

                words = s.split(/\s+/)

                words.each do |word|

                    # If the next word will run over the limit, break
                    # onto a new line.

                    if nextline.length > indent_length \
                    && nextline.length + word.length + 1 > 70

                        result += nextline + "\n"
                        nextline = " " * indent_length
                    end

                    # Space to separate from the previous word, but only
                    # if this is not the start of a line

                    if nextline.length > indent_length
                        if nextline[-1, 1] == "."

                            # Two spaces after a period

                            nextline += " "
                        end
                        nextline += " "
                    end

                    nextline += word
                end

                # Print the last "unfinished" line

                if nextline.length > indent_length
                    result += nextline + "\n"
                end
            end
        end

        result
    end

    def remove_trailing_newlines(s)
        while s[-2, 2] == "\n\n"
            s = s.chop
        end

        s
    end

    def print_change
        puts "#{@time} #{@author}"
        puts ""

        munged = combine_lines(@description)
        munged = break_lines(munged)
        munged = remove_trailing_newlines(munged)
        munged.each_line do |s|
            if s =~ /^\s*$/
                puts ""
            else
                puts "\t" + s
            end
        end

        puts
    end
end

changes = []

git_date_format = "Date:%ad%n" +
                  "Author:%an%n" +
                  "Text:%n%s%n%b___TEXT_END___"

git_command = "git log --pretty=format:#{git_date_format} --date=iso"

IO.popen(git_command) do |io|

    current_change = nil
    in_text = false

    io.each_line do |s|

        s = s.chomp

        if s =~ /^Date:(.*)/
            # start of a new change

            current_change = Change.new($1)
            changes.push(current_change)

        elsif s =~ /^Author:(.*)/
            current_change.author = $1
        elsif s =~ /^Text:/
            in_text = true
            current_change.description = ""
        elsif in_text
            if s == "___TEXT_END___"
                in_text = false
            else
                current_change.description += s + "\n"
            end
        end
    end
end

changes.each do |change|
    change.print_change
end