package service

import (
	"bytes"
	"context"
	"crypto/rand"
	"encoding/json"
	"fmt"
	"image"
	"image/color"
	"image/png"
	"io"
	"log"
	"net/http"
	"strings"
	"time"

	"gen2d/internal/config"
)

// imgCfg 保存文生图配置，由 main 通过 InitImageGenConfig 注入。
var imgCfg config.ImageGenConfig

// InitImageGenConfig 注入文生图配置。
func InitImageGenConfig(cfg config.ImageGenConfig) {
	imgCfg = cfg
}

// ======================== GPT Image 2 API 类型 ========================

// genSubmitReq 提交生图任务请求体。
type genSubmitReq struct {
	Prompt          string   `json:"prompt"`
	AspectRatio     string   `json:"aspect_ratio,omitempty"`
	ReferenceImages []string `json:"reference_images,omitempty"`
	XChannel        string   `json:"x_channel,omitempty"`
}

// genSubmitResp 提交生图任务响应体。
type genSubmitResp struct {
	Code    int    `json:"code"`
	Message string `json:"message"`
	Data    struct {
		TaskID string `json:"task_id"`
		Status string `json:"status"`
	} `json:"data"`
}

// genStatusReq 查询任务状态请求体。
type genStatusReq struct {
	TaskID string `json:"task_id"`
}

// genStatusResp 查询任务状态响应体。
type genStatusResp struct {
	Code    int    `json:"code"`
	Message string `json:"message"`
	Data    struct {
		TaskID         string `json:"task_id"`
		Status         string `json:"status"`
		Progress       int    `json:"progress"`
		ResultImageURL string `json:"result_image_url"`
		ErrorMessage   string `json:"error_message"`
	} `json:"data"`
}

// ======================== 文生图 ========================

// GenerateImages 通过 GPT Image 2 异步 API 生成图片，未配置 key 时回退到 mock。
func GenerateImages(ctx context.Context, prompt string, params AssetParams) ([]GeneratedImage, error) {
	count := 1
	if params.Frames.Directions > 0 && params.Frames.FramesPerDirection > 0 {
		count = params.Frames.Directions * params.Frames.FramesPerDirection
	}

	if imgCfg.APIKey != "" {
		log.Println("[inference] using image gen async API")
		return generateAsync(ctx, prompt, count, nil)
	}

	size := params.Resolution
	if size <= 0 {
		size = 64
	}
	log.Println("[inference] image API key not configured, using mock")
	return generateMockImages(size, count)
}

// ======================== 图片编辑 ========================

// EditImages 图片编辑接口，以参考图模式提交 GPT Image 2 编辑任务。
func EditImages(ctx context.Context, imageData []byte, prompt string, count int) ([]GeneratedImage, error) {
	if imgCfg.APIKey == "" {
		return nil, fmt.Errorf("image API key not configured")
	}
	log.Println("[inference] using image gen async API for edit")
	// 暂不支持参考图 URL 模式，提示用户
	return nil, fmt.Errorf("image edit with reference image: not yet implemented for async API")
}

// ======================== 异步核心 ========================

// generateAsync 并行提交 count 个任务，轮询完成后下载图片。
func generateAsync(ctx context.Context, prompt string, count int, refImages []string) ([]GeneratedImage, error) {
	type submitResult struct {
		index  int
		taskID string
		err    error
	}
	results := make(chan submitResult, count)
	for i := 0; i < count; i++ {
		go func(idx int) {
			taskID, err := submitTask(ctx, prompt, refImages)
			results <- submitResult{index: idx, taskID: taskID, err: err}
		}(i)
	}

	taskIDs := make([]string, count)
	for i := 0; i < count; i++ {
		r := <-results
		if r.err != nil {
			return nil, fmt.Errorf("submit task %d: %w", r.index, r.err)
		}
		taskIDs[r.index] = r.taskID
	}

	type imageResult struct {
		index int
		image GeneratedImage
		err   error
	}
	imgResults := make(chan imageResult, count)
	for i, tid := range taskIDs {
		go func(idx int, taskID string) {
			img, err := pollAndDownload(ctx, taskID)
			imgResults <- imageResult{index: idx, image: img, err: err}
		}(i, tid)
	}

	images := make([]GeneratedImage, count)
	for i := 0; i < count; i++ {
		r := <-imgResults
		if r.err != nil {
			return nil, fmt.Errorf("task %d: %w", r.index, r.err)
		}
		images[r.index] = r.image
	}

	return images, nil
}

// submitTask 提交生图任务，返回 taskID。
func submitTask(ctx context.Context, prompt string, refImages []string) (string, error) {
	reqBody := genSubmitReq{
		Prompt:          prompt,
		AspectRatio:     imgCfg.AspectRatio,
		ReferenceImages: refImages,
		XChannel:        imgCfg.XChannel,
	}

	body, err := json.Marshal(reqBody)
	if err != nil {
		return "", fmt.Errorf("marshal: %w", err)
	}

	url := strings.TrimRight(imgCfg.BaseURL, "/") + "/gpt-image2/generate"
	req, err := http.NewRequestWithContext(ctx, http.MethodPost, url, bytes.NewReader(body))
	if err != nil {
		return "", fmt.Errorf("create request: %w", err)
	}
	req.Header.Set("Content-Type", "application/json")
	req.Header.Set("Authorization", "Bearer "+imgCfg.APIKey)

	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		return "", fmt.Errorf("send: %w", err)
	}
	defer resp.Body.Close()

	var sr genSubmitResp
	if err := json.NewDecoder(resp.Body).Decode(&sr); err != nil {
		return "", fmt.Errorf("decode: %w", err)
	}

	if sr.Code != 200 {
		return "", fmt.Errorf("submit failed: %s", sr.Message)
	}

	log.Printf("[inference] task submitted: %s", sr.Data.TaskID)
	return sr.Data.TaskID, nil
}

// pollAndDownload 轮询任务直到完成，下载图片。
func pollAndDownload(ctx context.Context, taskID string) (GeneratedImage, error) {
	pollInterval := imgCfg.PollInterval
	if pollInterval <= 0 {
		pollInterval = 3
	}
	maxWait := imgCfg.PollMaxWait
	if maxWait <= 0 {
		maxWait = 120
	}

	deadline := time.Now().Add(time.Duration(maxWait) * time.Second)
	ticker := time.NewTicker(time.Duration(pollInterval) * time.Second)
	defer ticker.Stop()

	for {
		select {
		case <-ctx.Done():
			return GeneratedImage{}, ctx.Err()
		case <-ticker.C:
			st, err := queryStatus(ctx, taskID)
			if err != nil {
				return GeneratedImage{}, fmt.Errorf("query status: %w", err)
			}

			switch st.Data.Status {
			case "completed":
				log.Printf("[inference] task %s completed, downloading", taskID)
				data, err := downloadResult(ctx, st.Data.ResultImageURL)
				if err != nil {
					return GeneratedImage{}, fmt.Errorf("download: %w", err)
				}
				return GeneratedImage{Data: data, Format: "png"}, nil

			case "failed":
				errMsg := st.Data.ErrorMessage
				if errMsg == "" {
					errMsg = "unknown error"
				}
				return GeneratedImage{}, fmt.Errorf("generation failed: %s", errMsg)

			default:
				log.Printf("[inference] task %s status=%s progress=%d", taskID, st.Data.Status, st.Data.Progress)
			}

			if time.Now().After(deadline) {
				return GeneratedImage{}, fmt.Errorf("poll timeout after %ds", maxWait)
			}
		}
	}
}

// queryStatus 查询任务状态。
func queryStatus(ctx context.Context, taskID string) (*genStatusResp, error) {
	body, err := json.Marshal(genStatusReq{TaskID: taskID})
	if err != nil {
		return nil, fmt.Errorf("marshal: %w", err)
	}

	url := strings.TrimRight(imgCfg.BaseURL, "/") + "/gpt-image2/status"
	req, err := http.NewRequestWithContext(ctx, http.MethodPost, url, bytes.NewReader(body))
	if err != nil {
		return nil, fmt.Errorf("create request: %w", err)
	}
	req.Header.Set("Content-Type", "application/json")
	req.Header.Set("Authorization", "Bearer "+imgCfg.APIKey)

	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		return nil, fmt.Errorf("send: %w", err)
	}
	defer resp.Body.Close()

	var sr genStatusResp
	if err := json.NewDecoder(resp.Body).Decode(&sr); err != nil {
		return nil, fmt.Errorf("decode: %w", err)
	}

	if sr.Code != 200 {
		return nil, fmt.Errorf("status query failed: %s", sr.Message)
	}

	return &sr, nil
}

// downloadResult 下载生成的图片。
func downloadResult(ctx context.Context, imageURL string) ([]byte, error) {
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, imageURL, nil)
	if err != nil {
		return nil, fmt.Errorf("create download request: %w", err)
	}

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

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

	return io.ReadAll(resp.Body)
}

// ======================== 质检 ========================

// QualityChecker 质检函数，可替换用于测试。
var QualityChecker = defaultCheckQuality

// CheckQuality 调用当前 QualityChecker。
func CheckQuality(ctx context.Context, images []GeneratedImage, style map[string]string) (bool, string, error) {
	return QualityChecker(ctx, images, style)
}

func defaultCheckQuality(ctx context.Context, images []GeneratedImage, style map[string]string) (bool, string, error) {
	return true, "", nil
}

func NewCountedQualityChecker(passOnRetry int) func(context.Context, []GeneratedImage, map[string]string) (bool, string, error) {
	var callCount int
	return func(_ context.Context, _ []GeneratedImage, _ map[string]string) (bool, string, error) {
		callCount++
		if callCount >= passOnRetry {
			return true, "", nil
		}
		return false, fmt.Sprintf("style inconsistent (attempt %d)", callCount), nil
	}
}

func AlwaysFailQualityChecker() func(context.Context, []GeneratedImage, map[string]string) (bool, string, error) {
	return func(_ context.Context, _ []GeneratedImage, _ map[string]string) (bool, string, error) {
		return false, "style inconsistent", nil
	}
}

// ======================== Mock 回退 ========================

func generateMockImages(size, count int) ([]GeneratedImage, error) {
	images := make([]GeneratedImage, count)
	for i := 0; i < count; i++ {
		data, err := generateMockImage(size, i)
		if err != nil {
			return nil, fmt.Errorf("generate mock image %d: %w", i, err)
		}
		images[i] = GeneratedImage{Data: data, Width: size, Height: size, Format: "png"}
	}
	return images, nil
}

func generateMockImage(size int, seed int) ([]byte, error) {
	img := image.NewRGBA(image.Rect(0, 0, size, size))
	r := uint8((seed*47 + 13) % 256)
	g := uint8((seed*83 + 37) % 256)
	b := uint8((seed*61 + 71) % 256)
	for y := 0; y < size; y++ {
		for x := 0; x < size; x++ {
			img.Set(x, y, color.RGBA{R: r, G: g, B: b, A: 255})
		}
	}
	var buf bytes.Buffer
	if err := png.Encode(&buf, img); err != nil {
		return nil, err
	}
	return buf.Bytes(), nil
}

func generateRandomBytes(n int) ([]byte, error) {
	b := make([]byte, n)
	_, err := rand.Read(b)
	return b, err
}