package qyglreport

import (
	"encoding/base64"
	"html/template"
	"mime"
	"os"
	"path/filepath"
	"sync"

	"github.com/gin-gonic/gin"
)

const (
	defaultBannerRel = "resources/qygl-media/banner.jpg"
	defaultFooterRel = "resources/qygl-media/footer.png"
)

var (
	loadOnce   sync.Once
	bannerURL  template.URL
	footerURL  template.URL
)

func loadPosterAssets() {
	bannerURL = dataURLFromFile(resolveMediaFile([]string{
		defaultBannerRel,
		"resources/qygl-media/banner.png",
	}), "/reports/qygl/media/banner.jpg")
	footerURL = dataURLFromFile(defaultFooterRel, "/reports/qygl/media/footer.png")
}

func resolveMediaFile(candidates []string) string {
	for _, p := range candidates {
		if _, err := os.Stat(p); err == nil {
			return p
		}
	}
	if len(candidates) > 0 {
		return candidates[0]
	}
	return ""
}

func dataURLFromFile(path string, httpFallback string) template.URL {
	if path == "" {
		return template.URL(httpFallback)
	}
	data, err := os.ReadFile(path)
	if err != nil {
		return template.URL(httpFallback)
	}
	ext := filepath.Ext(path)
	mimeType := mime.TypeByExtension(ext)
	if mimeType == "" {
		switch ext {
		case ".jpg", ".jpeg":
			mimeType = "image/jpeg"
		case ".png":
			mimeType = "image/png"
		default:
			mimeType = "application/octet-stream"
		}
	}
	encoded := base64.StdEncoding.EncodeToString(data)
	return template.URL("data:" + mimeType + ";base64," + encoded)
}

// PageTemplateData 企业报告 HTML 模板数据（海报内嵌 data URL，PDF 生成不依赖外链）
func PageTemplateData(reportJSON template.JS) gin.H {
	loadOnce.Do(loadPosterAssets)
	return gin.H{
		"ReportJSON":      reportJSON,
		"BannerPosterURL": bannerURL,
		"FooterPosterURL": footerURL,
	}
}