package main

import (
	"bytes"
	"context"
	"errors"
	"fmt"
	"os"
	"os/exec"
	"path/filepath"
	"strconv"
	"strings"
	"time"
)

// gitRun 在指定仓库目录执行 git 命令，返回合并后的输出。
// 非交互环境：GIT_TERMINAL_PROMPT=0 只能挡住终端提示，挡不住 Windows 凭据管理器（GCM）弹窗，
// 因此额外禁用 GCM 交互、askpass 和 ssh 交互，避免后台同步被凭据弹窗永久卡死。
// WaitDelay 保证超时 Kill 后即使 git 的子进程仍占用管道，Wait() 也能强制返回（Windows 上
// CommandContext 只杀主进程，不杀 git-remote-https / 凭据 helper 等子进程）。
func gitRun(repoPath string, timeout time.Duration, args ...string) (string, error) {
	ctx, cancel := context.WithTimeout(context.Background(), timeout)
	defer cancel()
	full := append([]string{"-C", repoPath}, args...)
	cmd := exec.CommandContext(ctx, "git", full...)
	cmd.Env = append(os.Environ(),
		"GIT_TERMINAL_PROMPT=0",
		"GIT_ASKPASS=echo",
		"GCM_INTERACTIVE=never",
		"GIT_SSH_COMMAND=ssh -oBatchMode=yes -oStrictHostKeyChecking=accept-new",
	)
	cmd.WaitDelay = 10 * time.Second
	var buf bytes.Buffer
	cmd.Stdout = &buf
	cmd.Stderr = &buf
	err := cmd.Run()
	out := strings.TrimSpace(buf.String())
	if err != nil {
		if ctx.Err() == context.DeadlineExceeded {
			return out, fmt.Errorf("命令超时: git %s", strings.Join(args, " "))
		}
		msg := out
		if msg == "" {
			msg = err.Error()
		}
		return out, errors.New(msg)
	}
	return out, nil
}

func isRepo(path string) bool {
	if path == "" {
		return false
	}
	_, err := os.Stat(filepath.Join(path, ".git"))
	return err == nil
}

func currentBranch(path string) (string, error) {
	return gitRun(path, 15*time.Second, "rev-parse", "--abbrev-ref", "HEAD")
}

// aheadBehind 返回 (领先, 落后) 远程跟踪分支的提交数（需先 fetch 才准确）
func aheadBehind(path, remote, branch string) (int, int, error) {
	out, err := gitRun(path, 30*time.Second, "rev-list", "--left-right", "--count", "HEAD..."+remote+"/"+branch)
	if err != nil {
		return 0, 0, err
	}
	parts := strings.Fields(out)
	if len(parts) != 2 {
		return 0, 0, fmt.Errorf("无法解析 rev-list 输出: %q", out)
	}
	a, _ := strconv.Atoi(parts[0])
	b, _ := strconv.Atoi(parts[1])
	return a, b, nil
}

// remoteRefExists 检查远程跟踪引用是否存在（远程仓库为空或分支名不一致时为 false）
func remoteRefExists(path, remote, branch string) bool {
	_, err := gitRun(path, 15*time.Second, "rev-parse", "--verify", "-q", remote+"/"+branch)
	return err == nil
}

// branchExists 检查本地分支是否存在
func branchExists(path, branch string) bool {
	_, err := gitRun(path, 15*time.Second, "show-ref", "--verify", "-q", "refs/heads/"+branch)
	return err == nil
}

func dirtyCount(path string) int {
	out, err := gitRun(path, 30*time.Second, "status", "--porcelain")
	if err != nil {
		return 0
	}
	n := 0
	for _, line := range strings.Split(out, "\n") {
		if strings.TrimSpace(line) != "" {
			n++
		}
	}
	return n
}

var conflictCodes = map[string]bool{
	"DD": true, "AU": true, "UD": true, "UA": true, "DU": true, "AA": true, "UU": true,
}

func conflictFiles(path string) ([]string, error) {
	out, err := gitRun(path, 30*time.Second, "status", "--porcelain")
	if err != nil {
		return nil, err
	}
	var files []string
	seen := map[string]bool{}
	for _, line := range strings.Split(out, "\n") {
		if len(line) < 4 {
			continue
		}
		if !conflictCodes[line[:2]] {
			continue
		}
		p := strings.TrimSpace(line[3:])
		if i := strings.Index(p, "->"); i >= 0 {
			p = strings.TrimSpace(p[i+2:])
		}
		if p != "" && !seen[p] {
			seen[p] = true
			files = append(files, p)
		}
	}
	return files, nil
}

func abortMerge(path string) (string, error) {
	if out, err := gitRun(path, 30*time.Second, "rebase", "--abort"); err == nil {
		return out, nil
	}
	return gitRun(path, 30*time.Second, "merge", "--abort")
}

// resolveDone 在用户网页上标记"已解决"后调用：暂存全部 → 继续 merge/rebase 流程
func resolveDone(path string, rebase bool) error {
	if _, err := gitRun(path, 30*time.Second, "add", "-A"); err != nil {
		return err
	}
	if rebase {
		_, err := gitRun(path, 120*time.Second, "-c", "core.editor=true", "rebase", "--continue")
		return err
	}
	if _, err := gitRun(path, 15*time.Second, "rev-parse", "-q", "--verify", "MERGE_HEAD"); err == nil {
		_, err := gitRun(path, 120*time.Second, "commit", "--no-edit")
		return err
	}
	return nil
}