#!/bin/bash

## This script makes it so that you don't have to type
## long file paths into `git diff` anymore.
##
## Add this script anywhere on your system and then 
## in your ~/.gitconfig add the following:
##
## [alias]
##         diff-list = !/Full/Path/To/Script.sh
##
##
## Usage:
##
## In a git repository, you can now run:
##
## git diff-list
##
## This will give you a list of all un-staged files 
## you would normally see in `git status`, but with
## integer identifires before them.
##
## You can now run the following to see a diff for
## a file:
##
## git diff-list <id>
##
## Now you don't have to type long paths into `git diff`

main() {
    changed_files=$(git diff --color --name-status)
    total_changed=0
    for file in $changed_files; do 
        let total_changed=total_changed+1
    done

    if [ "$#" -ne 1 ]; then
        echo ""

        echo -e "> \033[1m\033[4mgit difflist <id>\033[0m to view the diff for any file (\033[1m\033[4m<id>\033[0m does not require leading 0s)"

        echo ""
        echo "Difference:"
        echo ""
        list_changes "$changed_files"

        echo ""
        exit
    fi

    if [ $1 -lt 0 ]; then
        echo "Invalid diff id, try again."
        exit 1
    fi

    if [ $1 -gt $total_changed ]; then
        echo "Invalid diff id, try again."
        exit 1
    fi

    file=$(get_file_diff "$changed_files" $1)
    if [[ "$file" != "0" ]]; then
        git diff $file
        exit 0
    fi

    echo "File does not contain any changes."
    exit 1
}

get_file_diff() {
    change=1
    IFS=$'\n'
    for file in $1; do 
        change_type=$(echo $file | awk '{printf $1}')
        file_name=$(echo $file | awk '{printf $2}')
        if [[ "$change" == "$2" ]]; then
            gitdir=${PWD##*/}
            echo ${file_name/$gitdir/"."}
            return
        fi
        let change=$change+1
    done

    echo "0"
}

list_changes() {
    change=1
    IFS=$'\n'
    for file in $1; do 
        change_type=$(echo $file | awk '{printf $1}')
        file_name=$(echo $file | awk '{printf $2}')
        printf "    [%04d] %s %s\n" $change $change_type $file_name
        let change=$change+1
    done
}

main $@