package prompt

import (
	"archive/zip"
	"bytes"
	"context"
	"fmt"
	"io"
	"net/http"
	"strings"
	"time"

	"github.com/gogf/gf/v2/frame/g"

	"prompts-core/common/util"
	"prompts-core/service/gateway"
)

const (
	bytesPerKB = 1024
	bytesPerMB = 1024 * 1024
)

// FetchFileTexts 从 URL 列表获取文件内容，支持 zip 内文件
func FetchFileTexts(ctx context.Context, urls []string) map[string]string {
	result := make(map[string]string)

	if len(urls) == 0 {
		return result
	}

	client := createHTTPClient(ctx, "userFiles.httpTimeoutSec", 8)

	for _, rawURL := range urls {
		url := util.SanitizeURL(rawURL)
		if url == "" || util.IsBannedExtension(url) {
			continue
		}

		if util.IsZipExtension(url) {
			mergeMap(result, fetchZipFileTexts(ctx, client, url))
			continue
		}

		if text := fetchAndCleanFileContent(ctx, client, url); text != "" {
			result[url] = text
		}
	}

	return result
}

// mergeMap 合并 map
func mergeMap(dst, src map[string]string) {
	for k, v := range src {
		dst[k] = v
	}
}

// fetchAndCleanFileContent 获取并清理文件内容
func fetchAndCleanFileContent(ctx context.Context, client *http.Client, url string) string {
	text, err := fetchFileContent(ctx, client, url)
	if err != nil || text == "" {
		return ""
	}
	return util.CleanSymbols(text)
}

// fetchZipFileTexts 下载并解压 zip 文件，提取可读文本内容
func fetchZipFileTexts(ctx context.Context, client *http.Client, url string) map[string]string {
	result := make(map[string]string)

	maxSize := int64(g.Cfg().MustGet(ctx, "userFiles.zipMaxSizeMB", 10).Int()) * bytesPerMB
	zipBytes, err := downloadFile(client, url, maxSize)
	if err != nil {
		return result
	}

	reader, err := zip.NewReader(bytes.NewReader(zipBytes), int64(len(zipBytes)))
	if err != nil {
		return result
	}

	entryMaxSize := int64(g.Cfg().MustGet(ctx, "userFiles.zipEntryMaxSizeKB", 500).Int()) * bytesPerKB

	for _, file := range reader.File {
		if shouldSkipZipEntry(file.Name) {
			continue
		}

		if text := extractZipEntryContent(file, entryMaxSize); text != "" {
			result[url+"::"+file.Name] = text
		}
	}

	return result
}

// shouldSkipZipEntry 判断是否应该跳过 zip 条目
func shouldSkipZipEntry(fileName string) bool {
	return util.IsBannedExtension(fileName) || util.IsZipExtension(fileName)
}

// extractZipEntryContent 提取 zip 条目内容
func extractZipEntryContent(file *zip.File, maxSize int64) string {
	rc, err := file.Open()
	if err != nil {
		return ""
	}
	defer rc.Close()

	content, err := io.ReadAll(io.LimitReader(rc, maxSize))
	if err != nil {
		return ""
	}

	if !util.IsReadableContentType(http.DetectContentType(content)) {
		return ""
	}

	text := util.CleanSymbols(string(content))
	if text == "" {
		return ""
	}

	return text
}

// downloadFile 下载文件，限制最大大小
func downloadFile(client *http.Client, url string, maxSize int64) ([]byte, error) {
	req, err := http.NewRequest(http.MethodGet, url, nil)
	if err != nil {
		return nil, fmt.Errorf("创建请求失败: %w", err)
	}

	resp, err := client.Do(req)
	if err != nil {
		return nil, fmt.Errorf("执行请求失败: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
		return nil, fmt.Errorf("HTTP %d", resp.StatusCode)
	}

	body, err := io.ReadAll(io.LimitReader(resp.Body, maxSize))
	if err != nil {
		return nil, fmt.Errorf("读取响应失败: %w", err)
	}

	return body, nil
}

// fetchFileContent 获取单个文本文件内容
func fetchFileContent(ctx context.Context, client *http.Client, url string) (string, error) {
	req, err := http.NewRequest(http.MethodGet, url, nil)
	if err != nil {
		return "", fmt.Errorf("创建请求失败: %w", err)
	}

	resp, err := client.Do(req)
	if err != nil {
		return "", fmt.Errorf("执行请求失败: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
		return "", fmt.Errorf("HTTP %d", resp.StatusCode)
	}

	contentType := resp.Header.Get("Content-Type")
	if !util.IsReadableContentType(contentType) {
		return "", fmt.Errorf("不可读的内容类型: %s", contentType)
	}

	maxSize := int64(g.Cfg().MustGet(ctx, "userFiles.textFileMaxSizeKB", 500).Int()) * bytesPerKB
	body, err := io.ReadAll(io.LimitReader(resp.Body, maxSize))
	if err != nil {
		return "", fmt.Errorf("读取响应失败: %w", err)
	}

	return strings.TrimSpace(string(body)), nil
}

// SkillMdContent 根据 skillName 获取 zip 内所有 md 文件拼接内容
func SkillMdContent(ctx context.Context, skillName string) string {
	skillResp, err := gateway.GetSkillUser(ctx, skillName)
	if err != nil {
		return ""
	}

	fullUrl := skillResp.ImgAddressPrefix + skillResp.FileUrl

	client := createHTTPClient(ctx, "skillFiles.httpTimeoutSec", 30)
	maxSize := int64(g.Cfg().MustGet(ctx, "skillFiles.zipMaxSizeMB", 10).Int()) * bytesPerMB

	zipBytes, err := downloadFile(client, fullUrl, maxSize)
	if err != nil {
		return ""
	}

	mdContents, err := extractMdFiles(ctx, zipBytes)
	if err != nil || len(mdContents) == 0 {
		return ""
	}

	return buildSkillMarkdown(skillResp, mdContents)
}

// buildSkillMarkdown 构建技能 Markdown 内容
func buildSkillMarkdown(skillResp *gateway.SkillUserVO, mdContents map[string]string) string {
	var builder strings.Builder

	builder.WriteString(fmt.Sprintf("# Skill: %s\n\n", skillResp.Name))
	if skillResp.Description != "" {
		builder.WriteString(fmt.Sprintf("> %s\n\n", skillResp.Description))
	}

	for fileName, content := range mdContents {
		builder.WriteString(fmt.Sprintf("## %s\n\n", fileName))
		builder.WriteString(content)
		builder.WriteString("\n\n---\n\n")
	}

	return strings.TrimSpace(builder.String())
}

// extractMdFiles 解压 zip 并提取所有 .md 文件内容
func extractMdFiles(ctx context.Context, zipBytes []byte) (map[string]string, error) {
	result := make(map[string]string)

	reader, err := zip.NewReader(bytes.NewReader(zipBytes), int64(len(zipBytes)))
	if err != nil {
		return nil, fmt.Errorf("创建 zip 阅读器失败: %w", err)
	}

	entryMaxSize := int64(g.Cfg().MustGet(ctx, "skillFiles.mdMaxSizeKB", 500).Int()) * bytesPerKB

	for _, file := range reader.File {
		if file.FileInfo().IsDir() || !isMarkdownFile(file.Name) {
			continue
		}

		if content := readMarkdownFileContent(file, entryMaxSize); content != "" {
			result[file.Name] = content
		}
	}

	return result, nil
}

// isMarkdownFile 判断是否为 Markdown 文件
func isMarkdownFile(fileName string) bool {
	return strings.HasSuffix(strings.ToLower(fileName), ".md")
}

// readMarkdownFileContent 读取 Markdown 文件内容
func readMarkdownFileContent(file *zip.File, maxSize int64) string {
	rc, err := file.Open()
	if err != nil {
		return ""
	}
	defer rc.Close()

	content, err := io.ReadAll(io.LimitReader(rc, maxSize))
	if err != nil {
		return ""
	}

	if len(content) == 0 {
		return ""
	}

	return strings.TrimSpace(string(content))
}

// createHTTPClient 创建 HTTP 客户端
func createHTTPClient(ctx context.Context, configKey string, defaultSeconds int) *http.Client {
	timeout := time.Duration(g.Cfg().MustGet(ctx, configKey, defaultSeconds).Int()) * time.Second
	return &http.Client{
		Timeout: timeout,
	}
}