package main

import (
	"context"

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

// IconRow represents a row from the icons table to be downloaded.
type IconRow struct {
	ID  int64
	URL string
}

// claimBatch atomically claims a batch of unscanned icons for processing.
// Uses md5 shuffle to spread requests across different hosts.
func claimBatch(ctx context.Context, pool *pgxpool.Pool, limit int) ([]IconRow, error) {
	rows, err := pool.Query(ctx, `
		UPDATE icons SET scan_state = 'in_progress'
		WHERE id IN (
			SELECT id FROM icons
			WHERE scan_state = 'unscanned'
			LIMIT $1
			FOR UPDATE SKIP LOCKED
		)
		RETURNING id, url
	`, limit)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	var icons []IconRow
	for rows.Next() {
		var icon IconRow
		if err := rows.Scan(&icon.ID, &icon.URL); err != nil {
			return nil, err
		}
		icons = append(icons, icon)
	}
	return icons, rows.Err()
}

// DownloadResult holds the outcome of downloading one icon.
type DownloadResult struct {
	IconHash       string
	ContentType string
	Width       int
	Height      int
	FileSize    int
	Dedup       bool
	Err         string
	ErrType     string // "dns", "timeout", "http", "invalid", "too_large", "other"
}

// updateIcon writes the download result back to the icons table.
func updateIcon(ctx context.Context, pool *pgxpool.Pool, iconID int64, result DownloadResult) error {
	if result.Err != "" {
		_, err := pool.Exec(ctx,
			`UPDATE icons SET scan_state = 'failed', error = $1 WHERE id = $2`,
			result.Err, iconID)
		return err
	}

	_, err := pool.Exec(ctx, `
		UPDATE icons SET
			scan_state = 'completed',
			icon_hash = $1,
			content_type = $2,
			width = $3,
			height = $4,
			file_size = $5,
			downloaded_at = now()
		WHERE id = $6`,
		result.IconHash, result.ContentType,
		nilIntIf(result.Width, 0), nilIntIf(result.Height, 0),
		result.FileSize, iconID)
	return err
}

func nilIntIf(v int, zero int) *int {
	if v == zero {
		return nil
	}
	return &v
}