// Command probe performs a dry run of the YouTube discovery + date-resolution
// logic for one or more channel/playlist URLs. It resolves every video's
// upload date and reports how many fall before/after a start date, without
// downloading anything.
//
// Usage:
//
//	probe <start-date YYYY-MM-DD> <url> [url ...]
package main

import (
	"context"
	"fmt"
	"os"
	"time"

	"rssd/ytdlp"
)

func main() {
	if len(os.Args) < 3 {
		fmt.Fprintln(os.Stderr, "usage: probe <start-date YYYY-MM-DD> <url> [url ...]")
		os.Exit(2)
	}
	start, err := time.Parse("2006-01-02", os.Args[1])
	if err != nil {
		fmt.Fprintln(os.Stderr, "bad start date:", err)
		os.Exit(2)
	}

	ctx, cancel := context.WithTimeout(context.Background(), 3*time.Hour)
	defer cancel()
	s := ytdlp.Settings{}

	for _, u := range os.Args[2:] {
		probeOne(ctx, s, u, start)
	}
}

func probeOne(ctx context.Context, s ytdlp.Settings, url string, start time.Time) {
	fmt.Printf("\n=== %s ===\n", url)
	vids, err := ytdlp.Discovery(ctx, s, url)
	if err != nil {
		fmt.Fprintf(os.Stderr, "  discovery error: %v\n", err)
		return
	}
	fmt.Printf("  discovered %d videos\n", len(vids))

	newestFirst := true
	for _, tok := range []string{"list="} {
		if contains(url, tok) {
			newestFirst = false
		}
	}
	fmt.Printf("  assumed newest-first: %v\n", newestFirst)

	total := 0
	inRange, beforeStart, noDate, failed := 0, 0, 0, 0
	var oldest, newest time.Time
	for _, v := range vids {
		total++
		info, err := ytdlp.Info(ctx, s, v.ID)
		if err != nil {
			failed++
			if failed <= 5 {
				fmt.Fprintf(os.Stderr, "  resolve warn %s: %v\n", v.ID, err)
			}
			continue
		}
		if info.UploadDate.IsZero() {
			noDate++
			continue
		}
		if oldest.IsZero() || info.UploadDate.Before(oldest) {
			oldest = info.UploadDate
		}
		if info.UploadDate.After(newest) {
			newest = info.UploadDate
		}
		if info.UploadDate.Before(start) {
			beforeStart++
			if newestFirst {
				// Channel is newest-first: everything after this is older, so stop.
				fmt.Printf("  reached pre-start-date boundary, stopping\n")
				break
			}
			continue
		}
		inRange++
		if inRange <= 5 {
			fmt.Printf("    IN  %s  %s  (%s)\n", info.UploadDate.Format("2006-01-02"), v.ID, trunc(v.Title, 60))
		}
	}
	fmt.Printf("  resolved=%d  inRange(>=%s)=%d  beforeStart=%d  noDate=%d  failed=%d\n",
		total, start.Format("2006-01-02"), inRange, beforeStart, noDate, failed)
	fmt.Printf("  oldest=%s  newest=%s\n", fmtDate(oldest), fmtDate(newest))
}

func contains(s, sub string) bool {
	for i := 0; i+len(sub) <= len(s); i++ {
		if s[i:i+len(sub)] == sub {
			return true
		}
	}
	return false
}

func trunc(s string, n int) string {
	if len(s) <= n {
		return s
	}
	return s[:n] + "…"
}

func fmtDate(t time.Time) string {
	if t.IsZero() {
		return "-"
	}
	return t.Format("2006-01-02")
}