package main

import (
	"fmt"
	"log"
	"os"
	"os/exec"
	"regexp"
	"sort"
	"strings"
)

func main() {
	rev := "HEAD"
	if len(os.Args) == 2 {
		rev = os.Args[1]
	}

	files := gitListFiles(rev)

	authors := gitBlameFiles(rev, files)

	sortedAuthors, keys := sortAuthors(authors)

	rank := 1

	for _, k := range keys {
		for i := 0; i < len(sortedAuthors[k]); i++ {
			fmt.Printf("%3d - %6d %s\n", rank, k, sortedAuthors[k][i])
			rank = rank + 1
		}
	}
}

func gitListFiles(rev string) []string {
	out, err := exec.Command("git", "ls-tree", "--name-only", "-r", rev).Output()
	if err != nil {
		log.Fatal(err)
	}
	files := strings.Split(string(out), "\n")
	return files
}

func gitBlameFiles(rev string, files []string) map[string]int {
	authors := make(map[string]int)

	for i := 0; i < len(files)-1; i++ {
		gitBlameFile(rev, files[i], authors)
	}
	return authors
}

func gitBlameFile(rev, file string, authors map[string]int) {
	out, err := exec.Command("git", "blame", "-e", "-w", rev, "--", file).Output()
	if err != nil {
		log.Fatal(err)
	}

	lines := strings.Split(string(out), "\n")

	authorRegex := regexp.MustCompile(`^.*?\((.*?)\s*\d{4}-\d{2}-\d{2}.*`)

	for j := 0; j < len(lines)-1; j++ {
		if string(lines[j][0]) != "^" {
			matched := authorRegex.FindStringSubmatch(string(lines[j]))
			if len(matched) > 0 {
				authors[matched[1]] = authors[matched[1]] + 1
			}
		}
	}
}

func sortAuthors(authors map[string]int) (map[int][]string, []int) {
	var keys []int
	sortedAuthors := make(map[int][]string)

	for k, v := range authors {
		sortedAuthors[v] = append(sortedAuthors[v], k)
		if len(sortedAuthors[v]) == 1 {
			keys = append(keys, v)
		}
	}
	sort.Sort(sort.Reverse(sort.IntSlice(keys)))

	return sortedAuthors, keys
}