package controlplane

import (
	"database/sql"
	"encoding/base64"
	"errors"
	"strings"
)

const (
	maxTaskImages     = 10
	maxTaskImageBytes = 12 * 1024 * 1024
)

// TaskImageInput is a browser data URL supplied only when creating a task.
// It is deliberately never copied to task output or audit fields.
type TaskImageInput struct {
	Name    string `json:"name"`
	DataURL string `json:"dataURL"`
}

type taskImage struct {
	Name      string `json:"name"`
	MediaType string `json:"media_type"`
	DataURL   string `json:"data_url"`
}

// TaskAttachment is the deliberately small preview returned only by the local
// task-detail view.  It is never used for audit records, task output, or logs.
// The data URL is needed by the local WebView to render a safe thumbnail.
type TaskAttachment struct {
	Name      string `json:"name"`
	MediaType string `json:"mediaType"`
	DataURL   string `json:"dataURL"`
}

func normalizeTaskImages(inputs []TaskImageInput) ([]taskImage, error) {
	if len(inputs) > maxTaskImages {
		return nil, errors.New("每项任务最多附加 10 张图片")
	}
	images := make([]taskImage, 0, len(inputs))
	total := 0
	for index, input := range inputs {
		parts := strings.SplitN(input.DataURL, ",", 2)
		if len(parts) != 2 || !strings.HasPrefix(parts[0], "data:") || !strings.HasSuffix(parts[0], ";base64") {
			return nil, errors.New("图片格式无效")
		}
		mediaType := strings.TrimSuffix(strings.TrimPrefix(parts[0], "data:"), ";base64")
		if mediaType != "image/png" && mediaType != "image/jpeg" && mediaType != "image/gif" && mediaType != "image/webp" {
			return nil, errors.New("只支持 PNG、JPEG、GIF 或 WebP 图片")
		}
		decoded, err := base64.StdEncoding.DecodeString(parts[1])
		if err != nil || len(decoded) == 0 {
			return nil, errors.New("图片内容无效")
		}
		total += len(decoded)
		if total > maxTaskImageBytes {
			return nil, errors.New("一项任务的图片总大小不能超过 12 MB")
		}
		name := strings.TrimSpace(input.Name)
		if name == "" {
			name = "图片" + stringLine(index+1)
		}
		images = append(images, taskImage{Name: name[:min(len(name), 120)], MediaType: mediaType, DataURL: input.DataURL})
	}
	return images, nil
}

func (c *ControlPlane) taskImages(taskID string) ([]taskImage, error) {
	rows, err := c.db.Query("SELECT name, media_type, data_url FROM task_images WHERE task_id = ? ORDER BY position", taskID)
	if err != nil {
		return nil, errors.New("无法读取任务图片")
	}
	defer rows.Close()
	images := make([]taskImage, 0)
	for rows.Next() {
		var image taskImage
		if err := rows.Scan(&image.Name, &image.MediaType, &image.DataURL); err != nil {
			return nil, errors.New("无法读取任务图片")
		}
		images = append(images, image)
	}
	if err := rows.Err(); err != nil && err != sql.ErrNoRows {
		return nil, errors.New("无法读取任务图片")
	}
	return images, nil
}

func (c *ControlPlane) taskAttachmentPreviews(taskID string) ([]TaskAttachment, error) {
	images, err := c.taskImages(taskID)
	if err != nil {
		return nil, err
	}
	previews := make([]TaskAttachment, 0, len(images))
	for _, image := range images {
		previews = append(previews, TaskAttachment{Name: image.Name, MediaType: image.MediaType, DataURL: image.DataURL})
	}
	return previews, nil
}