#!/usr/bin/env ruby

# USAGE:
#   git browse-remote [-r|--remote <remote>}] [--top|--rev|--ref] [<commit>]
#

require 'optparse'

class Path < Array
  def to_s
    join('/')
  end
end

remote = nil
mode = nil

# Variables available:
#  * host (eg. "github.com")
#  * path - Sliceable like an Array (eg. "motemen/git-browse-remote")
#  * ref (eg. "refs/heads/master")
#  * short_ref (eg. "master")
#  * commit (eg. "04f7c64ba9d524cf311a673ddce5722b2441e2ea")
MAPPING_RECIPES = {
  :github => {
    :top => 'https://{host}/{path}',
    :ref => 'https://{host}/{path}/tree/{short_ref}',
    :rev => 'https://{host}/{path}/commit/{commit}',
  },

  :gitweb => {
    :top => 'http://{host}/?p={path[-2..-1]}.git',
    :ref => 'http://{host}/?p={path[-2..-1]}.git;h={ref}',
    :rev => 'http://{host}/?p={path[-2..-1]}.git;a=commit;h={ref}',
  }
}

OptionParser.new do |opt|
  opt.banner = 'git browse-remote [options] [<commit> | <remote>]'
  opt.on('-r', '--remote=<remote>', 'specify remote') { |r| remote = r }
  opt.on('--top', 'open `top` page') { mode = :top }
  opt.on('--rev', 'open `rev` page') { mode = :rev }
  opt.on('--ref', 'open `ref` page') { mode = :ref }
  opt.on('--init [<host>=<recipe>]', 'initialize default url mappings') do |config|
    if config
      host, name = *config.split(/=/, 2)
    else
      host, name = 'github.com', 'github'
    end

    STDERR.puts "Writing config for #{host}..."

    mapping = MAPPING_RECIPES[name.to_sym] or abort "Recipe '#{name}' not found"
    mapping.each do |mode,template|
      system %Q(git config --global browse-remote.#{host}.#{mode} '#{template}')
    end

    STDERR.puts 'Mappings generated:'
    exec "git config --get-regexp ^browse-remote\\.#{host}\\."
  end
  opt.parse!(ARGV)
end

target = ARGV.shift || `git symbolic-ref -q HEAD`[/.+/]

if target
  if `git rev-parse --verify --quiet #{target}` && $? == 0
    # valid ref
    ref = `git rev-parse --symbolic-full-name #{target}`.chomp
  elsif `git config --get remote.#{target}.url`.chomp.empty? == false
    # not a valid ref, but valid remote
    ref = 'master'
    remote = target
    target = nil
  else
    abort "Not a valid ref or remote: #{target}"
  end
else
  ref = `git name-rev --name-only HEAD`.chomp.sub(%r(\^0$), '') # some workaround for ^0
end

commit = `git rev-parse #{target || 'HEAD'}`.chomp

if ref == 'HEAD'
  ref = nil
  short_ref = nil
else
  short_ref = ref.sub(%r(^refs/), '')

  if short_ref.sub!(%r(^heads/), '')
    mode ||= short_ref == 'master' ? :top : :ref
  end

  if short_ref.sub!(%r(^tags/), '')
    mode ||= :ref
  end

  if short_ref.sub!(%r(^remotes/([^/]+)/), '')
    remote ||= $1
    mode ||= short_ref == 'master' ? :top : :ref
  end

end

remote ||= 'origin'
mode   ||= :rev

remote_url = `git config remote.#{remote}.url`[/.+/] or
    abort "Could not get remote url: #{remote}"

host, *path = remote_url.sub(%r(^\w+://), '').sub(/^[\w-]+@/, '').split(/[\/:]+/)
path.last.sub!(/\.git$/, '')
path = Path.new(path)

template = `git config --get browse-remote.#{host}.#{mode}`[/.+/] or
    abort "No '#{mode}' mapping found for #{host} (maybe `git browse-remote --init` required)"

url = template.gsub(/{(.+?)}/) { |m| eval($1) }
exec 'git', 'web--browse', url