package main

import (
	"context"
	"time"

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

type HostRow struct {
	ID               int64
	Hostname         string
	Protocol         string
	HtmlTitle        string
	IframeAllowed    bool
	BestIconHash     string
	RandomOrder      float64
	IconDownloadedAt *time.Time
}

// fetchHostsPage gets a page of hosts with titles, ordered by icon_downloaded_at for disk locality.
// Icons written to disk at similar times are physically adjacent — reading in write order
// maximizes OS readahead cache hits. Hosts without icons come last (no disk reads needed).
// random_order is included for bundle bucket assignment (randomized bundles).
func fetchHostsPage(ctx context.Context, pool *pgxpool.Pool, lastDownloaded *time.Time, lastID int64, limit int) ([]HostRow, error) {
	rows, err := pool.Query(ctx, `
		SELECT id, hostname, protocol, html_title, COALESCE(iframe_allowed, true), COALESCE(best_icon_hash, ''), random_order, icon_downloaded_at
		FROM hosts
		WHERE html_title IS NOT NULL
		  AND (icon_downloaded_at, id) > ($1, $2)
		ORDER BY icon_downloaded_at NULLS LAST, id
		LIMIT $3
	`, lastDownloaded, lastID, limit)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	var hosts []HostRow
	for rows.Next() {
		var h HostRow
		if err := rows.Scan(&h.ID, &h.Hostname, &h.Protocol, &h.HtmlTitle, &h.IframeAllowed, &h.BestIconHash, &h.RandomOrder, &h.IconDownloadedAt); err != nil {
			return nil, err
		}
		hosts = append(hosts, h)
	}
	return hosts, rows.Err()
}