//
// Idempotent schema convergence for the scraper tables.
//
// There is no migration framework in this project and no schema file in git,
// so this runs at boot, checks information_schema for each object, and applies
// only what is missing. Dev and prod self-heal, and deploy.sh needs no change.
//
// Portability matters here: dev is MariaDB 11.4 and prod is MySQL 8.
// ADD COLUMN IF NOT EXISTS is MariaDB-only and is deliberately not used -
// every ALTER is guarded by an explicit existence check instead.
//

const db = require('@config/database')

let Schema = module.exports = {}

const SCRAPE_CACHE_TABLE = `
	CREATE TABLE IF NOT EXISTS scrape_cache (
		id            int(10) unsigned NOT NULL AUTO_INCREMENT,
		url_hash      char(64) NOT NULL,
		url           varchar(1000) NOT NULL DEFAULT '',
		canonical_url varchar(1000) DEFAULT NULL,
		status        smallint(6) NOT NULL DEFAULT 0,
		title         varchar(512) DEFAULT NULL,
		site_name     varchar(255) DEFAULT NULL,
		description   mediumtext DEFAULT NULL,
		keywords      varchar(512) DEFAULT NULL,
		search_text   mediumtext DEFAULT NULL,
		image_url     varchar(1000) DEFAULT NULL,
		file_location varchar(500) DEFAULT NULL,
		etag          varchar(255) DEFAULT NULL,
		last_modified varchar(128) DEFAULT NULL,
		content_type  varchar(128) DEFAULT NULL,
		fetch_state   varchar(20) NOT NULL DEFAULT 'pending',
		failure_count int(11) NOT NULL DEFAULT 0,
		last_error    varchar(255) DEFAULT NULL,
		fetched_at    int(11) DEFAULT NULL,
		expires_at    int(11) DEFAULT NULL,
		PRIMARY KEY (id),
		UNIQUE KEY scrape_cache_url_hash (url_hash),
		KEY scrape_cache_expires_at (expires_at),
		KEY scrape_cache_fetch_state (fetch_state)
	) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4
`

// DEFAULT 2 ("done") keeps existing rows out of the boot recovery sweep.
const ATTACHMENT_COLUMNS = [
	{ name: 'scrape_state', ddl: 'ALTER TABLE attachment ADD COLUMN scrape_state tinyint(4) NOT NULL DEFAULT 2' },
	{ name: 'scrape_attempts', ddl: 'ALTER TABLE attachment ADD COLUMN scrape_attempts tinyint(4) NOT NULL DEFAULT 0' },
	{ name: 'enqueued_at', ddl: 'ALTER TABLE attachment ADD COLUMN enqueued_at int(11) DEFAULT NULL' },
]

const ATTACHMENT_INDEXES = [
	{ name: 'attachment_scrape_state', ddl: 'ALTER TABLE attachment ADD KEY attachment_scrape_state (scrape_state, enqueued_at)' },
]

const columnExists = async (table, column) => {
	const [rows] = await db.promise().query(
		`SELECT 1 FROM information_schema.COLUMNS
		 WHERE TABLE_SCHEMA = DATABASE() AND TABLE_NAME = ? AND COLUMN_NAME = ? LIMIT 1`,
		[table, column]
	)
	return rows.length > 0
}

const indexExists = async (table, index) => {
	const [rows] = await db.promise().query(
		`SELECT 1 FROM information_schema.STATISTICS
		 WHERE TABLE_SCHEMA = DATABASE() AND TABLE_NAME = ? AND INDEX_NAME = ? LIMIT 1`,
		[table, index]
	)
	return rows.length > 0
}
Schema.__columnExists = columnExists
Schema.__indexExists = indexExists

//
// Safe to call repeatedly. Returns the list of statements it actually applied,
// so boot logging says something useful on the one run that matters.
//
Schema.ensureScrapeSchema = async () => {
	const applied = []

	await db.promise().query(SCRAPE_CACHE_TABLE)

	for (const column of ATTACHMENT_COLUMNS) {
		if (await columnExists('attachment', column.name)) { continue }
		await db.promise().query(column.ddl)
		applied.push(`attachment.${column.name}`)
	}

	// Index last: it references the columns above.
	for (const index of ATTACHMENT_INDEXES) {
		if (await indexExists('attachment', index.name)) { continue }
		await db.promise().query(index.ddl)
		applied.push(`attachment KEY ${index.name}`)
	}

	if (applied.length) {
		console.log('[schema] applied scrape schema changes:', applied.join(', '))
	}

	return applied
}