# The MIT License
# Copyright © 2009 Magnus Bergmark
# 
# 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.

class GitRemoteMonitor::GitWrapper
  class << self
    
    def local_branch
      branches = call_get_local_branch.split("\n")
      current = branches.detect { |branch| branch.strip.include? "* " }
      return nil unless current
      current.strip.slice(/^\* (.+)$/, 1)
    end
    
    def remote_branch
      branch = self.local_branch
      remote = call_get_remote(branch).strip
      return nil if remote.empty?
      "#{remote}/#{branch}"
    end
    
    def get_tracking_info(our_branch, their_branch)
      tracking_info = call_get_tracking_info(our_branch, their_branch).split("\n")
      if tracking_info.size > 2
        raise "Wrong number of lines returned while trying to look at tracking information!"
      elsif tracking_info.size == 2
        return [*tracking_info.collect { |line| line.gsub(/\D+/, '').to_i }]
      else
        # We have too look at which kind it is
        tracking_info = tracking_info.first
        if tracking_info and tracking_info.include? "<"
          return [tracking_info.gsub(/\D+/, '').to_i, 0]
        elsif tracking_info and tracking_info.include? ">"
          return [0, tracking_info.gsub(/\D+/, '').to_i]
        else
          return [0, 0]
        end
      end
    end
  
    #
    # Calls "git fetch" on the current working directory. Raises an error in case this
    # command ran unsuccessfully.
    #
    # The method will return true if a fetch was made or false if nothing was fetched.
    #
    def fetch!
      # If the output was empty, no actual fetch was done
      return !call_fetch.strip.empty?
    end
    
    private
      # Do the actual system call for "git fetch", returning output
      def call_fetch
        output = `git fetch 2>&1`
        raise "Could not fetch from remote! " + output unless $?.success?
        output
      end
      
      # Asks Git about tracking information for the given local branch and the specified
      # remote branch.
      #
      # Returns output formatted by `uniq -c` after looking at a list of commits
      # It should contain between 1 and 2 lines inclusive and look like this:
      #          4 <
      #          1 >
      #
      #  * The lines will be indented by spaces, then have a number, a space and a symbol.
      #  * When no branch have moved, the output will be on 1 line and have a 1 as the number
      #    and no symbol.
      #  * The symbols mean the following: "<" means local commits, ">" means remote commits
      def call_get_tracking_info(our, their)
        `git rev-list --left-right #{our}...#{their} | cut -c 1 | sort | uniq -c`
      end
      
      def call_get_local_branch
        `git branch --no-color`
      end
      
      def call_get_remote(local_name)
        `git config branch.#{local_name}.remote`
      end
  end
end