// Package git wraps basic Git operations via direct exec.Command,
// used by pkg/context to fill EnvInfo for system prompt injection
// and by future sandbox pod self-checkout audit hooks (DESIGN.md
// whitelist). pkg/memory/sync_git.go intentionally does NOT consume
// this package — it goes through execenv.Executor DI (ClassMemoryGit)
// for sandbox routing, keeping its own exec path.
//
// 包 git 通过裸 exec.Command 封装基础 Git 操作, 供 pkg/context
// 填充 EnvInfo 注入系统提示词, 以及未来 sandbox M2 "pod 自身
// checkout 审计白名单" 场景消费. 注意 pkg/memory/sync_git.go
// 刻意不走本包 — 它经 execenv.Executor DI (ClassMemoryGit) 执行,
// 保留 sandbox-aware 路由, 和本包 exec 路径独立.
package git

import (
	"fmt"
	"os/exec"
	"strconv"
	"strings"
)

// Info describes the current git repository summary used by context's
// EnvInfo to inject "Git repo / branch / status" into the system prompt.
//
// Info 描述当前 git 仓库摘要, 供 context.EnvInfo 注入系统提示词
// ("Git repo / branch / status" 字段).
type Info struct {
	IsRepo bool   // Whether cwd sits inside a git repo. / 是否在 git 仓库中.
	Branch string // Current branch name (empty on detached HEAD or non-repo). / 当前分支名 (detached HEAD 或非仓库时为空).
	Status string // git status --porcelain summary (empty means clean). / git status --porcelain 摘要 (空字符串即 clean).
}

// DetectRepo reports whether cwd sits inside a git work tree.
//
// DetectRepo 检测 cwd 是否位于 git 工作树内.
func DetectRepo(cwd string) bool {
	cmd := exec.Command("git", "rev-parse", "--is-inside-work-tree")
	cmd.Dir = cwd
	out, err := cmd.Output()
	if err != nil {
		return false
	}
	return strings.TrimSpace(string(out)) == "true"
}

// GetBranch returns the current branch name, or "" when in detached
// HEAD / non-repo. Uses `git branch --show-current` — the clean modern
// form where detached HEAD produces empty output (easier for callers
// than special-casing the literal "HEAD" returned by rev-parse).
//
// GetBranch 获取当前分支名; detached HEAD 或非仓库返回 "". 采用
// `git branch --show-current` 现代写法, detached HEAD 直接输出空串,
// 比 rev-parse 返回字面 "HEAD" 更易消费.
func GetBranch(cwd string) string {
	cmd := exec.Command("git", "branch", "--show-current")
	cmd.Dir = cwd
	out, err := cmd.Output()
	if err != nil {
		return ""
	}
	return strings.TrimSpace(string(out))
}

// GetStatus returns git status --porcelain output (empty == clean tree).
//
// GetStatus 返回 git status --porcelain 输出 (空字符串即 clean).
func GetStatus(cwd string) string {
	cmd := exec.Command("git", "status", "--porcelain")
	cmd.Dir = cwd
	out, err := cmd.Output()
	if err != nil {
		return ""
	}
	return strings.TrimSpace(string(out))
}

// GetInfo collects IsRepo / Branch / Status in one call. Used by
// pkg/context to fill EnvInfo for system prompt injection.
//
// GetInfo 一站式收集 IsRepo / Branch / Status 字段, 供 pkg/context
// 填充 EnvInfo 注入系统提示词.
func GetInfo(cwd string) *Info {
	info := &Info{}
	if !DetectRepo(cwd) {
		return info
	}
	info.IsRepo = true
	info.Branch = GetBranch(cwd)
	info.Status = GetStatus(cwd)
	return info
}

// ValidateRef guards ref args against path traversal and flag injection.
//
// ELEVATED: exec.Command separates argv (no shell), but a ref starting
// with ".." or "-" can still trigger git's own path/option parsing.
// Alternative rejected: strict regex whitelist ^[a-zA-Z0-9/_.-]+$ — would
// reject valid unicode branch names.
//
// ValidateRef 拦截 git ref 参数里的路径遍历和选项注入.
//
// 升华改进 (ELEVATED): exec.Command 按 argv 分离 (不经 shell),
// 但 ref 值含 ".." 或以 "-" 起头仍会命中 git 内部的路径 / 选项解析.
// 替代方案 (已否决): 正则白名单 ^[a-zA-Z0-9/_.-]+$ — 会误拦合法的 unicode 分支名.
func ValidateRef(ref string) error {
	if strings.Contains(ref, "..") {
		return fmt.Errorf("git: ref %q contains '..' (path traversal rejected)", ref)
	}
	if strings.HasPrefix(ref, "-") {
		return fmt.Errorf("git: ref %q starts with '-' (flag injection rejected)", ref)
	}
	return nil
}

// GetDiff returns git diff output vs optional ref (empty ref compares working tree to index).
//
// GetDiff 获取 git diff 输出 (空 ref 时对比工作区与暂存区).
func GetDiff(cwd, ref string) string {
	var cmd *exec.Cmd
	if ref == "" {
		cmd = exec.Command("git", "diff")
	} else {
		if err := ValidateRef(ref); err != nil {
			return ""
		}
		cmd = exec.Command("git", "diff", ref)
	}
	cmd.Dir = cwd
	out, err := cmd.Output()
	if err != nil {
		return ""
	}
	return strings.TrimSpace(string(out))
}

// GetLog returns the most recent n commits in --oneline format.
// n<=0 falls back to 10.
//
// GetLog 返回最近 n 条提交 (--oneline 格式); n<=0 回退到 10.
func GetLog(cwd string, n int) string {
	if n <= 0 {
		n = 10
	}
	cmd := exec.Command("git", "log", "--oneline", "-n", strconv.Itoa(n))
	cmd.Dir = cwd
	out, err := cmd.Output()
	if err != nil {
		return ""
	}
	return strings.TrimSpace(string(out))
}