package ingestion

import (
	"log/slog"
	"net/http"
	"net/url"
	"strconv"
	"strings"
	"time"
)

// NormalizeImageURL rewrites known CDN thumbnail URLs to a higher-resolution
// variant. Currently handles Guardian's i.guim.co.uk, whose RSS feeds hand out
// 140-px-wide thumbnails by default. Unrecognized hosts pass through unchanged.
func NormalizeImageURL(raw string) string {
	if raw == "" {
		return raw
	}
	u, err := url.Parse(raw)
	if err != nil || u.Host != "i.guim.co.uk" {
		return raw
	}
	q := u.Query()
	if q.Get("width") == "" {
		return raw
	}
	// The Guardian signs each (width, quality, fit, …) combination with `s=`.
	// Changing width without re-signing yields a 401 "invalid signature",
	// so leave signed URLs alone — the parser is now responsible for picking
	// the widest media:content variant up front.
	if q.Get("s") != "" {
		return raw
	}
	q.Set("width", "1200")
	u.RawQuery = q.Encode()
	return u.String()
}

var imageClient = &http.Client{
	Timeout: 10 * time.Second,
	CheckRedirect: func(req *http.Request, via []*http.Request) error {
		if len(via) >= 3 {
			return http.ErrUseLastResponse
		}
		return nil
	},
}

// ValidateImageURL checks that an image URL returns a valid image response.
// Returns false (with no error) on any failure — story posts without image.
func ValidateImageURL(url string) bool {
	if url == "" {
		return false
	}

	req, err := http.NewRequest("HEAD", url, nil)
	if err != nil {
		slog.Debug("image validation: bad url", "url", url, "err", err)
		return false
	}
	req.Header.Set("User-Agent", userAgent)

	resp, err := imageClient.Do(req)
	if err != nil {
		slog.Warn("image validation: request failed", "url", url, "err", err)
		return false
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		slog.Warn("image validation: bad status", "url", url, "status", resp.StatusCode)
		return false
	}

	contentType := resp.Header.Get("Content-Type")
	if !strings.HasPrefix(contentType, "image/") {
		slog.Warn("image validation: not an image", "url", url, "content_type", contentType)
		return false
	}

	// Filter tracking pixels: Content-Length must be > 5KB if present
	if cl := resp.Header.Get("Content-Length"); cl != "" {
		size, err := strconv.ParseInt(cl, 10, 64)
		if err == nil && size <= 5120 {
			slog.Warn("image validation: small image (≤5KB), skipping", "url", url, "size", size)
			return false
		}
	}

	return true
}