package main

import (
	"context"
	"flag"
	"fmt"
	"log"
	"os"
	"sync"
	"sync/atomic"
	"time"

	"github.com/jackc/pgx/v5/pgxpool"
)

type Config struct {
	DBUrl       string
	BatchSize   int
	Concurrency int
	WriteBatch  int
	Limit       int
	DryRun      bool
	LogFile     string
	LogErrors   bool
}

type Stats struct {
	Processed     atomic.Int64
	TitlesFound   atomic.Int64
	NoTitle       atomic.Int64
	IconsFound    atomic.Int64
	IframeBlocked atomic.Int64
	ParseErrors   atomic.Int64
	FetchErrors   atomic.Int64
	DBErrors      atomic.Int64
	Panics        atomic.Int64
	StartedAt     time.Time
}

func main() {
	cfg := Config{}
	flag.StringVar(&cfg.DBUrl, "db", "", "Postgres connection string (required)")
	flag.IntVar(&cfg.BatchSize, "batch-size", 5000, "Rows to fetch per batch")
	flag.IntVar(&cfg.Concurrency, "concurrency", 500, "Number of concurrent goroutines")
	flag.IntVar(&cfg.WriteBatch, "write-batch", 1000, "Results to batch per DB write")
	flag.IntVar(&cfg.Limit, "limit", 0, "Max rows to process (0 = all)")
	flag.BoolVar(&cfg.DryRun, "dry-run", false, "Print results without writing to DB")
	flag.StringVar(&cfg.LogFile, "log-file", "", "Mirror log lines to this file")
	flag.BoolVar(&cfg.LogErrors, "log-errors-only", false, "Only write errors to log file")
	flag.Parse()

	if cfg.DBUrl == "" {
		fmt.Println("Usage: warc_parse --db DATABASE_URL [OPTIONS]")
		flag.PrintDefaults()
		os.Exit(1)
	}

	ctx := context.Background()

	// Init S3 client
	if err := initS3(); err != nil {
		log.Fatalf("Failed to init S3: %v", err)
	}

	pool, err := pgxpool.New(ctx, cfg.DBUrl)
	if err != nil {
		log.Fatalf("Failed to connect to database: %v", err)
	}
	defer pool.Close()

	fmt.Printf("=== WARC Parser ===\n")
	fmt.Printf("Concurrency: %d\n", cfg.Concurrency)
	fmt.Printf("Batch size: %d\n", cfg.BatchSize)
	fmt.Printf("Write batch: %d\n", cfg.WriteBatch)
	if cfg.Limit > 0 {
		fmt.Printf("Limit: %d\n", cfg.Limit)
	}
	fmt.Printf("Dry run: %v\n\n", cfg.DryRun)

	// Setup log file
	var logWriter *LogWriter
	if cfg.LogFile != "" {
		logWriter, err = NewLogWriter(cfg.LogFile, cfg.LogErrors)
		if err != nil {
			log.Fatalf("Failed to open log file: %v", err)
		}
		defer logWriter.Close()
	}

	// Disable autovacuum during heavy writes — it competes for disk I/O
	// and causes writer stalls. Re-enabled + manual VACUUM at end.
	if !cfg.DryRun {
		fmt.Println("Disabling autovacuum on hosts and icons tables...")
		pool.Exec(ctx, "ALTER TABLE hosts SET (autovacuum_enabled = false)")
		pool.Exec(ctx, "ALTER TABLE icons SET (autovacuum_enabled = false)")
	}

	stats := &Stats{StartedAt: time.Now()}

	// Three-stage pipeline:
	//   [DB fetcher] → hostCh → [N workers] → resultCh → [DB writer]
	// Workers do S3 fetch + parsing (I/O-bound). Writer batches DB writes.

	hostCh := make(chan Host, 20000)
	resultCh := make(chan WorkResult, 1000)

	// Stage 1: DB fetcher — continuously fetches pages into hostCh
	go func() {
		defer close(hostCh)
		var lastID int64
		fetched := 0
		for {
			limit := cfg.BatchSize
			if cfg.Limit > 0 {
				remaining := cfg.Limit - fetched
				if remaining <= 0 {
					break
				}
				if limit > remaining {
					limit = remaining
				}
			}
			fetchStart := time.Now()
			hosts, err := fetchBatch(ctx, pool, lastID, limit)
			if err != nil {
				log.Fatalf("Failed to fetch batch: %v", err)
			}
			if len(hosts) == 0 {
				break
			}
			lastID = hosts[len(hosts)-1].ID
			fmt.Printf("[fetcher] %d hosts in %dms (hostCh: %d/%d)\n",
				len(hosts), time.Since(fetchStart).Milliseconds(), len(hostCh), cap(hostCh))
			for _, h := range hosts {
				hostCh <- h
			}
			fetched += len(hosts)
		}
	}()

	// Stage 2: Workers — fetch WARC from S3, parse HTML, emit results
	var workerWg sync.WaitGroup
	for i := 0; i < cfg.Concurrency; i++ {
		workerWg.Add(1)
		go func() {
			defer workerWg.Done()
			for host := range hostCh {
				func() {
					defer func() {
						if r := recover(); r != nil {
							stats.Panics.Add(1)
							stats.Processed.Add(1)
							logLine := fmt.Sprintf("PANIC: %s %v", host.Hostname, r)
							fmt.Println(logLine)
							if logWriter != nil {
								logWriter.Write(logLine, true)
							}
						}
					}()

					result := processHost(host)

					// Log
					logLine := formatLogLine(host, result)
					fmt.Println(logLine)
					if logWriter != nil {
						logWriter.Write(logLine, result.Err != nil)
					}

					// Update stats
					stats.Processed.Add(1)
					if result.Err == nil {
						if result.Title != "" {
							stats.TitlesFound.Add(1)
						} else {
							stats.NoTitle.Add(1)
						}
						stats.IconsFound.Add(int64(len(result.Icons) + 1))
						if !result.IframeAllowed {
							stats.IframeBlocked.Add(1)
						}
					} else if result.FetchErr {
						stats.FetchErrors.Add(1)
					} else {
						stats.ParseErrors.Add(1)
					}

					// Send successful results to writer
					if result.Err == nil {
						resultCh <- WorkResult{Host: host, Result: result}
					}
				}()
			}
		}()
	}
	go func() {
		workerWg.Wait()
		close(resultCh)
	}()

	// Stage 3: DB writers — multiple goroutines batch writes for efficiency
	const numWriters = 3
	var writerWg sync.WaitGroup
	if !cfg.DryRun {
		for w := 0; w < numWriters; w++ {
			writerWg.Add(1)
			go func() {
				defer writerWg.Done()
				var buf []WorkResult
				for wr := range resultCh {
					buf = append(buf, wr)
					if len(buf) >= cfg.WriteBatch {
						flushStart := time.Now()
						dbErrs := flushResults(ctx, pool, buf, logWriter)
						stats.DBErrors.Add(int64(dbErrs))
						flushMs := time.Since(flushStart).Milliseconds()
						if flushMs > 100 {
							fmt.Printf("[writer] flushed %d results in %dms (resultCh: %d/%d)\n",
								len(buf), flushMs, len(resultCh), cap(resultCh))
						}
						buf = buf[:0]
					}
				}
				if len(buf) > 0 {
					dbErrs := flushResults(ctx, pool, buf, logWriter)
					stats.DBErrors.Add(int64(dbErrs))
				}
			}()
		}
	} else {
		writerWg.Add(1)
		go func() {
			defer writerWg.Done()
			for range resultCh {
			}
		}()
	}
	writerWg.Wait()

	// Re-enable autovacuum and run manual vacuum
	if !cfg.DryRun {
		fmt.Println("Re-enabling autovacuum and running VACUUM ANALYZE...")
		pool.Exec(ctx, "ALTER TABLE hosts SET (autovacuum_enabled = true)")
		pool.Exec(ctx, "ALTER TABLE icons SET (autovacuum_enabled = true)")
		pool.Exec(ctx, "VACUUM ANALYZE hosts")
		pool.Exec(ctx, "VACUUM ANALYZE icons")
		fmt.Println("VACUUM complete")
	}

	// Print summary
	duration := time.Since(stats.StartedAt)
	fmt.Printf("\n=== Summary ===\n")
	fmt.Printf("Duration: %s\n", duration.Round(time.Second))
	fmt.Printf("Processed: %d\n", stats.Processed.Load())
	fmt.Printf("Titles found: %d\n", stats.TitlesFound.Load())
	fmt.Printf("No title: %d\n", stats.NoTitle.Load())
	fmt.Printf("Icons found: %d\n", stats.IconsFound.Load())
	fmt.Printf("Iframe blocked: %d\n", stats.IframeBlocked.Load())
	fmt.Printf("Fetch errors: %d\n", stats.FetchErrors.Load())
	fmt.Printf("Parse errors: %d\n", stats.ParseErrors.Load())
	fmt.Printf("DB errors: %d\n", stats.DBErrors.Load())
	fmt.Printf("Panics: %d\n", stats.Panics.Load())

	// Write stats JSON
	writeStats(stats, cfg)
}