import type Database from 'better-sqlite3';

const historyTables = ['beta_servers', 'deployment_servers', 'server_deployments', 'leaderboard_matches', 'watchdog_incidents', 'maintenance_jobs'];
const now = "strftime('%Y-%m-%dT%H:%M:%fZ','now')";

/** Detach durable beta records without dropping their evidence, indexes, or activity triggers. */
function detachBetaHistory(handle: Database.Database): void {
    for (const name of ['beta_servers', 'beta_test_runs', 'beta_server_scripts']) {
        const { sql } = handle.prepare("SELECT sql FROM sqlite_master WHERE type = 'table' AND name = ?").get(name) as { sql: string };
        const replacement = sql.replace(/server\s+TEXT NOT NULL REFERENCES servers\(name\)/, 'server TEXT NOT NULL');
        if (replacement === sql) continue;
        const dependents = handle.prepare("SELECT sql FROM sqlite_master WHERE tbl_name = ? AND type IN ('index','trigger') AND sql IS NOT NULL")
            .all(name) as { sql: string }[];
        const columns = (handle.prepare(`PRAGMA table_info(${name})`).all() as { name: string }[]).map(col => col.name).join(', ');
        handle.pragma('foreign_keys = OFF');
        try {
            handle.transaction(() => {
                handle.exec(replacement.replace(name, name + '_history_new'));
                handle.exec(`INSERT INTO ${name}_history_new (rowid, ${columns}) SELECT rowid, ${columns} FROM ${name};
                    DROP TABLE ${name}; ALTER TABLE ${name}_history_new RENAME TO ${name};`);
                for (const dependent of dependents) handle.exec(dependent.sql);
                if ((handle.pragma('foreign_key_check') as unknown[]).length) throw new Error('Server history migration found broken references');
            })();
        } finally { handle.pragma('foreign_keys = ON'); }
    }
}

// A rebuild owns the replacement instance. Only its current operation and the
// Watchdog records observing it cross the deliberate gap in the live registry.
const removingRebuild = `SELECT d.id FROM server_deployments d
    JOIN server_rebuild_jobs r ON r.deployment_id = d.id
    WHERE d.server = OLD.name AND d.server_deleted_at IS NULL AND d.action = 'rebuild'
        AND d.state IN ('waiting','running','failed','interrupted')
        AND d.stage = 'Removing server files and registry' AND r.removed_at IS NULL
        AND NOT EXISTS (SELECT 1 FROM server_deployments newer WHERE newer.server = d.server
            AND newer.rowid > d.rowid)`;

/** Installed after additive migrations so existing databases can boot safely. */
export function migrateServerHistory(handle: Database.Database): void {
    detachBetaHistory(handle);
    handle.transaction(() => {
        for (const table of historyTables) {
            const columns = handle.prepare(`PRAGMA table_info(${table})`).all() as { name: string }[];
            if (!columns.some(column => column.name === 'server_deleted_at')) handle.exec(`ALTER TABLE ${table} ADD COLUMN server_deleted_at TEXT`);
        }
        const collectionColumns = handle.prepare('PRAGMA table_info(server_launch_collections)').all() as { name: string }[];
        if (!collectionColumns.some(column => column.name === 'retained_server_deletions')) {
            handle.exec("ALTER TABLE server_launch_collections ADD COLUMN retained_server_deletions TEXT NOT NULL DEFAULT '{}'");
        }
        // Historical unfinished work cannot claim the next server with this name.
        handle.exec(`DROP INDEX IF EXISTS idx_maintenance_pending;
            CREATE UNIQUE INDEX idx_maintenance_pending ON maintenance_jobs(server)
                WHERE state IN ('queued', 'restarting') AND server_deleted_at IS NULL;
            DROP INDEX IF EXISTS idx_watchdog_active;
            CREATE UNIQUE INDEX idx_watchdog_active ON watchdog_incidents(server,kind)
                WHERE state != 'resolved' AND server_deleted_at IS NULL;
            DROP TRIGGER IF EXISTS preserve_deleted_server_history;
            CREATE TRIGGER preserve_deleted_server_history BEFORE DELETE ON servers
            BEGIN
                UPDATE server_launch_collections SET retained_server_deletions = json_patch(retained_server_deletions, json_object(OLD.name, ${now}))
                    WHERE EXISTS (SELECT 1 FROM json_each(retained_servers) WHERE value = OLD.name)
                        AND NOT EXISTS (SELECT 1 FROM json_each(retained_server_deletions) WHERE key = OLD.name);
                UPDATE beta_servers SET server_deleted_at = ${now} WHERE server = OLD.name AND server_deleted_at IS NULL;
                UPDATE deployment_servers SET server_deleted_at = ${now}
                    WHERE server = OLD.name AND server_deleted_at IS NULL AND deployment_id NOT IN (
                        SELECT campaign_id FROM watchdog_actions WHERE campaign_id IS NOT NULL AND operation_id IN (${removingRebuild}));
                UPDATE watchdog_incidents SET server_deleted_at = ${now}
                    WHERE server = OLD.name AND server_deleted_at IS NULL AND id NOT IN (
                        SELECT incident_id FROM watchdog_actions WHERE operation_id IN (${removingRebuild}));
                UPDATE maintenance_jobs SET server_deleted_at = ${now},
                    finished_at = CASE WHEN state IN ('queued','restarting') THEN ${now} ELSE finished_at END,
                    detail = CASE WHEN state IN ('queued','restarting') THEN COALESCE(detail || '; ', '') || 'Server deleted' ELSE detail END,
                    state = CASE WHEN state IN ('queued','restarting') THEN 'cancelled' ELSE state END
                    WHERE server = OLD.name AND server_deleted_at IS NULL;
                UPDATE leaderboard_matches SET server_deleted_at = ${now},
                    ended_at = CASE WHEN status = 'active' THEN COALESCE(ended_at, ${now}) ELSE ended_at END,
                    status = CASE WHEN status = 'active' THEN 'interrupted' ELSE status END
                    WHERE server = OLD.name AND server_deleted_at IS NULL;
                INSERT INTO server_deployment_events (deployment_id, created_at, message)
                    SELECT id, ${now}, 'Cancelled: server deleted' FROM server_deployments
                    WHERE server = OLD.name AND server_deleted_at IS NULL AND state IN ('queued','waiting','running','awaiting-health')
                        AND id NOT IN (${removingRebuild})
                        AND NOT (action = 'destroy' AND state = 'running' AND stage = 'Removing server files and registry');
                UPDATE server_deployments SET state = 'cancelled', error = 'Server deleted', finished_at = ${now}
                    WHERE server = OLD.name AND server_deleted_at IS NULL AND state IN ('queued','waiting','running','awaiting-health')
                        AND id NOT IN (${removingRebuild})
                        AND NOT (action = 'destroy' AND state = 'running' AND stage = 'Removing server files and registry');
                UPDATE server_deployments SET server_deleted_at = ${now}
                    WHERE server = OLD.name AND server_deleted_at IS NULL AND id NOT IN (${removingRebuild});
            END;`);
        if (!handle.prepare("SELECT 1 FROM settings WHERE key = 'server_history_v1'").get()) {
            // Recover the availability of history already orphaned before this
            // migration. Queued launches and rebuild registry gaps are not deletions.
            const liveRebuilds = `SELECT d.id FROM server_deployments d JOIN server_rebuild_jobs r ON r.deployment_id = d.id
                WHERE d.server_deleted_at IS NULL AND d.action = 'rebuild' AND (d.state IN ('waiting','queued','running','awaiting-health')
                    OR (d.state IN ('failed','interrupted') AND d.stage = 'Removing server files and registry'))
                    AND NOT EXISTS (SELECT 1 FROM server_deployments newer WHERE newer.server = d.server AND newer.rowid > d.rowid)`;
            for (const table of historyTables) {
                const exception = table === 'server_deployments'
                    ? `AND (action != 'create' OR state IN ('done','warning') OR EXISTS (
                            SELECT 1 FROM server_deployments removal WHERE removal.server = server_deployments.server
                                AND removal.rowid > server_deployments.rowid AND removal.action = 'destroy' AND removal.state IN ('done','warning')))
                        AND id NOT IN (${liveRebuilds})`
                    : table === 'deployment_servers'
                        ? `AND deployment_id NOT IN (SELECT campaign_id FROM watchdog_actions WHERE campaign_id IS NOT NULL AND operation_id IN (${liveRebuilds}))`
                        : table === 'watchdog_incidents'
                            ? `AND id NOT IN (SELECT incident_id FROM watchdog_actions WHERE operation_id IN (${liveRebuilds}))` : '';
                handle.exec(`UPDATE ${table} SET server_deleted_at = ${now} WHERE server_deleted_at IS NULL
                    AND NOT EXISTS (SELECT 1 FROM servers WHERE name = ${table}.server AND destroyed_at IS NULL) ${exception}`);
            }
            handle.exec(`UPDATE server_launch_collections SET retained_server_deletions = json_patch(retained_server_deletions,
                (SELECT json_group_object(value, ${now}) FROM json_each(retained_servers) retained
                    WHERE NOT EXISTS (SELECT 1 FROM servers WHERE name = retained.value AND destroyed_at IS NULL)
                        AND NOT EXISTS (SELECT 1 FROM server_deployments d WHERE d.server = retained.value
                            AND d.server_deleted_at IS NULL AND d.action IN ('create','rebuild')
                            AND d.state IN ('queued','running','awaiting-health','waiting'))
                        AND NOT EXISTS (SELECT 1 FROM json_each(retained_server_deletions) WHERE key = retained.value)));`);
            handle.exec(`UPDATE maintenance_jobs SET state = 'cancelled', finished_at = ${now}, detail = COALESCE(detail || '; ', '') || 'Server deleted'
                    WHERE server_deleted_at IS NOT NULL AND state IN ('queued','restarting');
                UPDATE leaderboard_matches SET status = 'interrupted', ended_at = COALESCE(ended_at, server_deleted_at)
                    WHERE server_deleted_at IS NOT NULL AND status = 'active';
                INSERT INTO server_deployment_events (deployment_id, created_at, message)
                    SELECT id, ${now}, 'Cancelled: server deleted' FROM server_deployments
                    WHERE server_deleted_at IS NOT NULL AND state IN ('queued','waiting','running','awaiting-health');
                UPDATE server_deployments SET state = 'cancelled', error = 'Server deleted', finished_at = ${now}
                    WHERE server_deleted_at IS NOT NULL AND state IN ('queued','waiting','running','awaiting-health');
                INSERT INTO settings (key, value) VALUES ('server_history_v1', '1');`);
        }
    })();
}