package main

import (
	"context"
	"fmt"

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

// Host represents a row from the hosts table.
type Host struct {
	ID               int64
	Hostname         string
	Protocol         string
	WarcFilename     string
	WarcRecordOffset int64
	WarcRecordLength int
}

// ProcessResult holds everything extracted from one host's WARC record.
type ProcessResult struct {
	Title         string
	IframeAllowed bool
	Icons         []Icon
	Err           error
	FetchErr      bool // true if error was during fetch (vs parse)
}

// fetchBatch gets the next batch of unparsed hosts after lastID.
func fetchBatch(ctx context.Context, pool *pgxpool.Pool, lastID int64, limit int) ([]Host, error) {
	rows, err := pool.Query(ctx,
		`SELECT id, hostname, protocol, warc_filename, warc_record_offset, warc_record_length
		 FROM hosts
		 WHERE parsed = FALSE AND id > $1
		 ORDER BY id
		 LIMIT $2`,
		lastID, limit)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	var hosts []Host
	for rows.Next() {
		var h Host
		err := rows.Scan(&h.ID, &h.Hostname, &h.Protocol, &h.WarcFilename, &h.WarcRecordOffset, &h.WarcRecordLength)
		if err != nil {
			return nil, err
		}
		hosts = append(hosts, h)
	}
	return hosts, rows.Err()
}

// WorkResult pairs a host with its parsed result for the DB writer.
type WorkResult struct {
	Host   Host
	Result ProcessResult
}

// flushResults writes a batch of successful results to the database.
// Host UPDATEs use pgx.Batch. Icon INSERTs use pgx.CopyFrom for bulk throughput.
// Returns the number of DB errors encountered.
func flushResults(ctx context.Context, pool *pgxpool.Pool, results []WorkResult, logWriter *LogWriter) int {
	dbErrors := 0

	// 1. Batch UPDATE hosts (can't COPY an UPDATE)
	batch := &pgx.Batch{}
	for _, wr := range results {
		batch.Queue(
			`UPDATE hosts SET html_title = $1, iframe_allowed = $2, parsed = TRUE WHERE id = $3`,
			nilIfEmpty(wr.Result.Title), wr.Result.IframeAllowed, wr.Host.ID,
		)
	}
	br := pool.SendBatch(ctx, batch)
	for _, wr := range results {
		if _, err := br.Exec(); err != nil {
			dbErrors++
			logLine := fmt.Sprintf("DB_ERROR: %s hosts_update: %v", wr.Host.Hostname, err)
			fmt.Println(logLine)
			if logWriter != nil {
				logWriter.Write(logLine, true)
			}
		}
	}
	br.Close()

	// 2. COPY icons in bulk (much less IOPS than individual INSERTs)
	var iconRows [][]any
	for _, wr := range results {
		// favicon.ico entry
		faviconURL := fmt.Sprintf("%s://%s/favicon.ico", wr.Host.Protocol, wr.Host.Hostname)
		iconRows = append(iconRows, []any{wr.Host.ID, faviconURL, "favicon_ico", nil, nil})
		// link_rel entries
		for _, icon := range wr.Result.Icons {
			iconRows = append(iconRows, []any{wr.Host.ID, icon.URL, icon.Source, nilIfEmpty(icon.RelType), nilIfEmpty(icon.RelSizes)})
		}
	}

	_, err := pool.CopyFrom(ctx,
		pgx.Identifier{"icons"},
		[]string{"host_id", "url", "source", "rel_type", "rel_sizes"},
		pgx.CopyFromRows(iconRows),
	)
	if err != nil {
		dbErrors++
		logLine := fmt.Sprintf("DB_ERROR: icon COPY failed (%d rows): %v", len(iconRows), err)
		fmt.Println(logLine)
		if logWriter != nil {
			logWriter.Write(logLine, true)
		}
	}

	return dbErrors
}

func nilIfEmpty(s string) *string {
	if s == "" {
		return nil
	}
	return &s
}