package main

import (
	"bufio"
	"bytes"
	"errors"
	"fmt"
	"os"
	"os/exec"
	"regexp"
	"sort"
	"strconv"
	"strings"
)

func runGit(args ...string) (string, error) {
	cmd := exec.Command("git", args...)
	cmd.Stderr = os.Stderr
	out, err := cmd.Output()
	if err != nil {
		return "", fmt.Errorf("git %s failed: %w", strings.Join(args, " "), err)
	}
	return string(out), nil
}

func inGitRepo() bool {
	cmd := exec.Command("git", "rev-parse", "--is-inside-work-tree")
	cmd.Stderr = nil
	out, err := cmd.Output()
	if err != nil {
		return false
	}
	return strings.TrimSpace(string(out)) == "true"
}

func currentBranch() (string, error) {
	out, err := runGit("rev-parse", "--abbrev-ref", "HEAD")
	if err != nil {
		return "", err
	}
	return strings.TrimSpace(out), nil
}

func fetchPrune() error {
	fmt.Println("Git fetch with prune...")
	cmd := exec.Command("git", "fetch", "--prune")
	cmd.Stdout = os.Stdout
	cmd.Stderr = os.Stderr
	return cmd.Run()
}

func parseGoneBranches(branchVV string) ([]string, error) {
	lines := strings.Split(branchVV, "\n")
	var branches []string

	re := regexp.MustCompile(`^\s*([^\s]+)\s+[0-9a-f]+\s+\[[^\]]*: gone\]`)
	for _, line := range lines {
		line = strings.TrimSpace(line)
		if line == "" {
			continue
		}
		line = strings.TrimPrefix(line, "* ")
		m := re.FindStringSubmatch(line)
		if len(m) == 2 {
			branches = append(branches, m[1])
		}
	}
	sort.Strings(branches)
	return branches, nil
}

func readLine(prompt string) (string, error) {
	fmt.Print(prompt)
	r := bufio.NewReader(os.Stdin)
	s, err := r.ReadString('\n')
	if err != nil {
		return "", err
	}
	return strings.TrimSpace(s), nil
}

func parseSelection(input string, max int) (map[int]bool, error) {
	input = strings.TrimSpace(input)
	if input == "" {
		return nil, errors.New("No Selection")
	}

	if strings.EqualFold(input, "all") {
		sel := make(map[int]bool, max)
		for i := 1; i <= max; i++ {
			sel[i] = true
		}
		return sel, nil
	}

	sel := make(map[int]bool)
	parts := strings.Split(input, ",")
	for _, p := range parts {
		p = strings.TrimSpace(p)
		if p == "" {
			continue
		}
		if strings.Contains(p, "-") {
			b := strings.SplitN(p, "-", 2)
			if len(b) != 2 {
                return nil, fmt.Errorf("Invalid Range: %s", p)
			}
			start, err := strconv.Atoi(strings.TrimSpace(b[0]))
			if err != nil {
				return nil, fmt.Errorf("Invalid Number: %s", b[0])
			}
			end, err := strconv.Atoi(strings.TrimSpace(b[1]))
			if err != nil {
				return nil, fmt.Errorf("Invalid Number: %s", b[1])
			}
			if start < 1 || end > max || start > end {
				return nil, fmt.Errorf("Range outside of 1..%d: %s", max, p)
			}
			for i := start; i <= end; i++ {
				sel[i] = true
			}
		} else {
			n, err := strconv.Atoi(p)
			if err != nil {
				return nil, fmt.Errorf("Invalid Number: %s", p)
			}
			if n < 1 || n > max {
				return nil, fmt.Errorf("Range outside of 1..%d: %d", max, n)
			}
			sel[n] = true
		}
	}
	return sel, nil
}

func deleteBranch(name string, force bool) error {
	args := []string{"branch"}
	if force {
		args = append(args, "-D")
	} else {
		args = append(args, "-d")
	}
	args = append(args, name)

	cmd := exec.Command("git", args...)
	cmd.Stdout = os.Stdout
	cmd.Stderr = os.Stderr
	return cmd.Run()
}

func main() {

	force := false
	autoAll := false
	showOnly := false
	info := false

	for _, a := range os.Args[1:] {
		switch a {
		case "--force":
			force = true
		case "--all":
			autoAll = true
		case "--info":
			info = true
		case "--show":
			showOnly = true
		case "--help", "-h":
            fmt.Println("Usage: cleanupGoneBranches [--show] [--all] [--force]")
            fmt.Println("  --show   only displays gone branches")
            fmt.Println("  --info   displays the manual Git commands for the same workflow")
            fmt.Println("  --all    deletes all gone branches without prompting for selection, but still asks for confirmation")
            fmt.Println("  --force  uses git branch -D instead of -d")
			os.Exit(0)
		default:
			fmt.Fprintf(os.Stderr, "Unkown Argument: %s\n", a)
			os.Exit(2)
		}
	}

	if info {
        fmt.Println("Manual Git commands for the same workflow:")
        fmt.Println()
        fmt.Println("1) Update remote branches and remove stale references:")
        fmt.Println("   git fetch --prune")
        fmt.Println()
        fmt.Println("2) Show gone branches:")
        fmt.Println("   git branch -vv")
        fmt.Println("   (Branches marked with '[origin/xyz: gone]' are orphaned local branches)")
        fmt.Println()
        fmt.Println("3) Delete a single branch (safe, only if it has been merged):")
        fmt.Println("   git branch -d <branch-name>")
        fmt.Println()
        fmt.Println("4) Force deletion (even if it has not been merged):")
        fmt.Println("   git branch -D <branch-name>")
        fmt.Println()
        fmt.Println("5) Automatically delete all gone branches:")
        fmt.Println(`   git branch -vv | awk '/: gone]/{print $1}' | xargs -r git branch -D`)
		fmt.Println()
		return
	}

    if !inGitRepo() {
        fmt.Fprintln(os.Stderr, "Error: This is not a Git repository (or you are not inside the working tree).")
        os.Exit(1)
    }

    if err := fetchPrune(); err != nil {
        fmt.Fprintln(os.Stderr, "Fetch failed:", err)
        os.Exit(1)
    }

    vv, err := runGit("branch", "-vv")
    if err != nil {
        fmt.Fprintln(os.Stderr, "Failed to run git branch -vv:", err)
        os.Exit(1)
    }

    gone, err := parseGoneBranches(vv)
    if err != nil {
        fmt.Fprintln(os.Stderr, "Failed to parse gone branches:", err)
        os.Exit(1)
    }

    if len(gone) == 0 {
        fmt.Println("No gone branches found.")
        return
    }

	cur, _ := currentBranch()

	fmt.Println()
	fmt.Println("Local branches found with a deleted remote (gone):")
	fmt.Println()

	for i, b := range gone {
		marker := ""
		if b == cur {
			marker = "  (current branch, skipped)"
		}
		fmt.Printf("  %2d) %s%s\n", i+1, b, marker)
	}

	if showOnly {
		return
	}

	indexToBranch := make([]string, 0, len(gone))
	for _, b := range gone {
		indexToBranch = append(indexToBranch, b)
	}

	var selected map[int]bool
	if autoAll {
		selected = make(map[int]bool, len(indexToBranch))
		for i := 1; i <= len(indexToBranch); i++ {
			selected[i] = true
		}
	} else {
		fmt.Println()
        fmt.Println("Enter your selection, e.g. 1,3-5 or all. Leave blank to cancel.")
        in, rerr := readLine("Selection: ")
        if rerr != nil {
            fmt.Fprintln(os.Stderr, "Input failed:", rerr)
            os.Exit(1)
        }
        if strings.TrimSpace(in) == "" {
            fmt.Println("Cancelled, nothing was deleted.")
            return
        }
        selected, err = parseSelection(in, len(indexToBranch))
        if err != nil {
            fmt.Fprintln(os.Stderr, "Invalid selection:", err)
            os.Exit(2)
        }
	}

	var toDelete []string
	for idx := range selected {
		b := indexToBranch[idx-1]
		if b == cur {
			continue
		}
		toDelete = append(toDelete, b)
	}
	sort.Strings(toDelete)

    if len(toDelete) == 0 {
        fmt.Println("Nothing to delete (current branch will not be deleted).")
        return
    }

    fmt.Println()
    fmt.Println("The following branches will be deleted:")
    for _, b := range toDelete {
        fmt.Println("  -", b)
    }

    fmt.Println()
    confirm, _ := readLine("Really delete? (y/N): ")
    if !strings.EqualFold(confirm, "y") {
        fmt.Println("Cancelled, nothing was deleted.")
        return
    }

    fmt.Println()
    fmt.Println("Deleting branches...")
    var failed bytes.Buffer
    for _, b := range toDelete {
        if err := deleteBranch(b, force); err != nil {
            failed.WriteString(b)
            failed.WriteString("\n")
        }
    }

    if failed.Len() > 0 {
        fmt.Println()
        fmt.Println("Done, but these branches could not be deleted:")
        fmt.Print(failed.String())
        fmt.Println("Tip: without --force, Git only deletes branches it considers safe.")
    } else {
        fmt.Println("Done.")
    }
}