package internal

import (
	"crypto/sha256"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"os"
	"runtime"
	"strings"
	"time"

	"charm.land/bubbletea/v2"
)

// Version 当前版本，发布时更新
const Version = "0.1.0"

// --- 远程 JSON 结构 ---

type platformInfo struct {
	DownloadURL string `json:"download_url"`
	FileSize    int64  `json:"file_size"`
	SHA256      string `json:"sha256"`
}

type versionInfo struct {
	Version      string                  `json:"version"`
	ReleaseDate  string                  `json:"release_date"`
	Changelog    string                  `json:"changelog"`
	Platforms    map[string]platformInfo `json:"platforms"`
}

// --- bubbletea 消息类型 ---

// UpdateAvailableMsg 发现新版本
type UpdateAvailableMsg struct {
	NewVersion  string
	Changelog   string
	DownloadURL string
	SHA256      string
	FileSize    int64
}

// UpdateCompleteMsg 更新完成
type UpdateCompleteMsg struct {
	NewVersion string
}

// UpdateErrorMsg 更新失败
type UpdateErrorMsg struct {
	Err error
}

// --- 更新状态 ---

// UpdateState 更新流程状态
type UpdateState struct {
	Checking    bool
	Available   bool
	Updating    bool
	NewVersion  string
	Changelog   string
	DownloadURL string
	SHA256      string
	FileSize    int64
	Done        bool
	Error       error
}

// --- Cmd 函数 ---

// CheckUpdateCmd 检查远程是否有新版本，返回 bubbletea Cmd
func CheckUpdateCmd() tea.Cmd {
	return func() tea.Msg {
		client := &http.Client{Timeout: 10 * time.Second}

		req, err := http.NewRequest("GET", "https://c.1216.top/u-tabs/last-version.json", nil)
		if err != nil {
			return nil
		}
		req.Header.Set("User-Agent", "u-tabs/"+Version)

		resp, err := client.Do(req)
		if err != nil {
			return nil
		}
		defer resp.Body.Close()

		if resp.StatusCode != http.StatusOK {
			return nil
		}

		body, err := io.ReadAll(resp.Body)
		if err != nil {
			return nil
		}

		var info versionInfo
		if err := json.Unmarshal(body, &info); err != nil {
			return nil
		}

		// 查找当前平台的下载信息
		platformKey := runtime.GOOS + "-" + runtime.GOARCH
		pi, ok := info.Platforms[platformKey]
		if !ok {
			return nil
		}

		// 比较版本
		if !semverCompare(Version, info.Version) {
			return nil
		}

		return UpdateAvailableMsg{
			NewVersion:  info.Version,
			Changelog:   info.Changelog,
			DownloadURL: pi.DownloadURL,
			SHA256:      pi.SHA256,
			FileSize:    pi.FileSize,
		}
	}
}

// SelfUpdateCmd 下载并替换当前二进制，返回 bubbletea Cmd
func SelfUpdateCmd(downloadURL, expectedSHA256, newVersion string) tea.Cmd {
	return func() tea.Msg {
		// 下载到临时文件
		client := &http.Client{Timeout: 5 * time.Minute}

		req, err := http.NewRequest("GET", downloadURL, nil)
		if err != nil {
			return UpdateErrorMsg{Err: fmt.Errorf("create request failed: %w", err)}
		}
		req.Header.Set("User-Agent", "u-tabs/"+Version)

		resp, err := client.Do(req)
		if err != nil {
			return UpdateErrorMsg{Err: fmt.Errorf("download failed: %w", err)}
		}
		defer resp.Body.Close()

		if resp.StatusCode != http.StatusOK {
			return UpdateErrorMsg{Err: fmt.Errorf("download returned status %d", resp.StatusCode)}
		}

		tmpFile, err := os.CreateTemp("", "u-tabs-update-*")
		if err != nil {
			return UpdateErrorMsg{Err: fmt.Errorf("create temp file failed: %w", err)}
		}
		tmpPath := tmpFile.Name()

		hasher := sha256.New()
		if _, err := io.Copy(io.MultiWriter(tmpFile, hasher), resp.Body); err != nil {
			tmpFile.Close()
			os.Remove(tmpPath)
			return UpdateErrorMsg{Err: fmt.Errorf("download write failed: %w", err)}
		}
		tmpFile.Close()

		// 校验 SHA256
		actualSHA := fmt.Sprintf("%x", hasher.Sum(nil))
		if !strings.EqualFold(actualSHA, expectedSHA256) {
			os.Remove(tmpPath)
			return UpdateErrorMsg{Err: fmt.Errorf("sha256 mismatch: expected %s, got %s", expectedSHA256, actualSHA)}
		}

		// 替换当前二进制
		exePath, err := os.Executable()
		if err != nil {
			os.Remove(tmpPath)
			return UpdateErrorMsg{Err: fmt.Errorf("get executable path failed: %w", err)}
		}

		// 备份旧二进制
		oldPath := exePath + ".old"
		_ = os.Remove(oldPath) // 清理可能残留的旧备份
		if err := os.Rename(exePath, oldPath); err != nil {
			os.Remove(tmpPath)
			return UpdateErrorMsg{Err: fmt.Errorf("rename old binary failed: %w", err)}
		}

		// 复制新二进制到原路径
		if err := copyFile(tmpPath, exePath); err != nil {
			// 回滚：恢复旧二进制
			os.Remove(exePath)
			os.Rename(oldPath, exePath)
			os.Remove(tmpPath)
			return UpdateErrorMsg{Err: fmt.Errorf("copy new binary failed: %w", err)}
		}

		// Linux/macOS: 设置可执行权限
		if runtime.GOOS != "windows" {
			os.Chmod(exePath, 0755)
		}

		// 清理临时文件和旧备份
		os.Remove(tmpPath)
		_ = os.Remove(oldPath)

		return UpdateCompleteMsg{NewVersion: newVersion}
	}
}

// --- 辅助函数 ---

// semverCompare 比较 v1 和 v2，v2 > v1 时返回 true
func semverCompare(v1, v2 string) bool {
	parts1 := strings.Split(v1, ".")
	parts2 := strings.Split(v2, ".")

	maxLen := len(parts1)
	if len(parts2) > maxLen {
		maxLen = len(parts2)
	}

	for i := 0; i < maxLen; i++ {
		var n1, n2 int
		if i < len(parts1) {
			n1 = parseSemverPart(parts1[i])
		}
		if i < len(parts2) {
			n2 = parseSemverPart(parts2[i])
		}
		if n2 > n1 {
			return true
		}
		if n2 < n1 {
			return false
		}
	}
	return false // 版本相同
}

// parseSemverPart 解析语义版本的一段为数字，非数字前缀的部分返回 0
func parseSemverPart(s string) int {
	// 去除可能的前缀字母 (如 "v1" → "1")
	n := 0
	for _, c := range s {
		if c >= '0' && c <= '9' {
			n = n*10 + int(c-'0')
		} else {
			break
		}
	}
	return n
}

// copyFile 复制文件内容
func copyFile(src, dst string) error {
	in, err := os.Open(src)
	if err != nil {
		return err
	}
	defer in.Close()

	out, err := os.Create(dst)
	if err != nil {
		return err
	}
	defer out.Close()

	if _, err := io.Copy(out, in); err != nil {
		return err
	}
	return out.Sync()
}