// Copyright 2025 linux.do
// Copyright 2026 Arctel.net
// SPDX-License-Identifier: Apache-2.0

package task

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"strings"
	"sync"

	"github.com/Rain-kl/Wavelet/internal/apps/upload/filesrv"
	"github.com/Rain-kl/Wavelet/internal/apps/upload/shared"
	"github.com/Rain-kl/Wavelet/internal/infra/task"
	"github.com/Rain-kl/Wavelet/internal/repository"
)

const (
	// WarmImageCacheTask 图片压缩缓存预热任务标识
	WarmImageCacheTask = "upload:warm_image_cache"
	// TaskTypeWarmImageCache 图片压缩缓存预热管理类型
	TaskTypeWarmImageCache = "warm_image_cache"
)

var warmImageCacheMu sync.Mutex

// WarmImageCacheMeta represents the image cache warmup task metadata.
var WarmImageCacheMeta = task.TaskMeta{
	Type:         TaskTypeWarmImageCache,
	AsynqTask:    WarmImageCacheTask,
	Name:         "Warm up compressed image cache",
	Description:  "Sequentially convert managed images to WebP at the specified quality and store them in permanent cache",
	SupportsTime: false,
	MaxRetry:     task.DefaultMaxRetry,
	Queue:        task.QueueDefault,
	Retryable:    true,
	Params: []task.TaskParam{
		{
			Name:        "quality",
			Label:       "Image quality",
			Type:        "string",
			Required:    true,
			Placeholder: "low / medium / high",
			Description: "WebP compression quality; must be low, medium or high",
		},
	},
}

// WarmImageCachePayload is the image cache warmup task payload.
type WarmImageCachePayload struct {
	Quality string `json:"quality"`
}

// WarmImageCacheHandler serially warms compressed image cache entries.
type WarmImageCacheHandler struct{}

// ValidatePayload validates and normalizes image cache warmup parameters.
func (h *WarmImageCacheHandler) ValidatePayload(payload []byte) ([]byte, error) {
	if len(payload) == 0 {
		return nil, errors.New(shared.ErrImageCacheWarmupPayloadRequired)
	}

	var req WarmImageCachePayload
	if err := json.Unmarshal(payload, &req); err != nil {
		return nil, fmt.Errorf(shared.ErrInvalidImageCacheWarmupPayload, err)
	}

	req.Quality = strings.ToLower(strings.TrimSpace(req.Quality))
	if req.Quality != shared.ImageQualityLow &&
		req.Quality != shared.ImageQualityMedium &&
		req.Quality != shared.ImageQualityHigh {
		return nil, errors.New(shared.ErrInvalidImageCacheWarmupQuality)
	}

	return json.Marshal(req)
}

// Execute serially converts all managed images to WebP cache entries.
func (h *WarmImageCacheHandler) Execute(ctx context.Context, payload []byte) (*task.TaskResult, error) {
	normalizedPayload, err := h.ValidatePayload(payload)
	if err != nil {
		task.AppendLog(ctx, "Invalid image cache warmup parameters: %v", err)
		return nil, err
	}

	var req WarmImageCachePayload
	if err := json.Unmarshal(normalizedPayload, &req); err != nil {
		return nil, fmt.Errorf(shared.ErrParseImageCacheWarmupPayload, err)
	}

	task.AppendLog(ctx, "Waiting for image cache warmup lock, quality: %s", req.Quality)
	warmImageCacheMu.Lock()
	defer warmImageCacheMu.Unlock()

	const (
		batchSize      = 50
		maxFailureLogs = 5
	)
	var lastID uint64
	var totalProcessed int
	var totalCached int
	var totalGenerated int
	var totalFailed int

	task.AppendLog(ctx, "Starting sequential compressed image cache warmup, quality: %s, batch size: %d", req.Quality, batchSize)

	for {
		if err := ctx.Err(); err != nil {
			return nil, fmt.Errorf("image cache warmup canceled: %w", err)
		}

		uploads, err := repository.ListActiveImageUploadsAfterID(ctx, lastID, batchSize)
		if err != nil {
			task.AppendLog(ctx, "Failed to query image upload records: %v", err)
			return nil, fmt.Errorf(shared.ErrQueryImagesForCacheWarmup, err)
		}

		if len(uploads) == 0 {
			break
		}

		batchGenerated := 0
		batchCached := 0
		batchFailed := 0
		for i := range uploads {
			if err := ctx.Err(); err != nil {
				return nil, fmt.Errorf("image cache warmup canceled: %w", err)
			}

			upload := &uploads[i]
			totalProcessed++
			lastID = upload.ID

			_, cacheHit, err := filesrv.EnsureCompressedImageCache(ctx, upload, req.Quality)
			if err != nil {
				totalFailed++
				batchFailed++
				if totalFailed <= maxFailureLogs {
					task.AppendLog(ctx, "Failed to process image [ID:%d]: %v", upload.ID, err)
				}
				continue
			}
			if cacheHit {
				totalCached++
				batchCached++
				continue
			}
			totalGenerated++
			batchGenerated++
		}

		task.AppendLog(
			ctx,
			"Batch completed, last ID: %d, generated: %d, hits: %d, failed: %d",
			lastID,
			batchGenerated,
			batchCached,
			batchFailed,
		)
	}

	msg := fmt.Sprintf(
		"Image cache warmup completed; processed %d, generated %d, hits %d, failed %d",
		totalProcessed,
		totalGenerated,
		totalCached,
		totalFailed,
	)
	task.AppendLog(ctx, "%s", msg)
	return &task.TaskResult{Message: msg}, nil
}