<?php
/**
 * Feature flags manager for WPDO module lifecycle states.
 *
 * @package WP_Data_Optimizer
 */

declare(strict_types=1);

if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

/**
 * Feature flags for each WPDO module.
 *
 * Option key: wpdo_features (serialized array)
 *
 * 7-state lifecycle per module (extends HPCT's 4-state model):
 *   idle → dual_write → backfill → verify → cutover → cleanup → complete
 *
 * Any state can roll back to idle.
 */
class TMDO_Feature_Flags {

	/** Option name storing all module states. */
	private const OPTION_KEY = 'wpdo_features';

	/**
	 * Modules driven by AddOn interceptors (WooCommerce commissions, LatePoint).
	 */
	public const ADDON_MODULES = array(
		'wc_orders',
		'latepoint',
	);

	/**
	 * Zone-based modules (new in WPDO).
	 * These modules operate on wpdo_* tables.
	 */
	public const ZONE_MODULES = array(
		'hot_hp_listing',
		'hot_hp_vendor',
		'warm',
		'cold_hp_listing',
		'cold_hp_vendor',
		'archive',
	);

	/** Valid lifecycle states. */
	public const VALID_STATES = array(
		'idle',
		'dual_write',
		'backfill',
		'verify',
		'cutover',
		'cleanup',
		'complete',
	);

	/**
	 * States in which interceptors should capture writes (dual-write active).
	 */
	public const WRITE_ACTIVE_STATES = array(
		'dual_write',
		'backfill',
		'verify',
		'cutover',
	);

	/**
	 * States in which reads come from the custom/zone table.
	 */
	public const READ_CUSTOM_STATES = array(
		'cutover',
		'cleanup',
		'complete',
	);

	/**
	 * States in which query interceptors are active.
	 */
	public const QUERY_ACTIVE_STATES = array(
		'cutover',
		'cleanup',
		'complete',
	);

	/**
	 * Get the state of a single module.
	 *
	 * @param string $module Module name.
	 * @return string One of VALID_STATES, defaults to 'idle'.
	 */
	public static function get( string $module ): string {
		$flags = self::all();
		return $flags[ $module ] ?? 'idle';
	}

	/**
	 * Set the state of a module.
	 *
	 * V2.2.0 M2: gated by TMDO_FSM_Guard — invalid transitions are blocked
	 * (returns false), destructive transitions automatically snapshot first.
	 * Filter `wpdo/fsm_guard/bypass` allows CLI/tests to override.
	 *
	 * @param string $module Module name.
	 * @param string $state  One of VALID_STATES.
	 * @return bool|WP_Error true on success, WP_Error on guard rejection,
	 *                       false on invalid state name.
	 */
	public static function set( string $module, string $state ) {
		if ( ! in_array( $state, self::VALID_STATES, true ) ) {
			return false;
		}

		// FSM Guard: validate transition + auto-snapshot if destructive.
		// Defensive: only invoke when class is loaded AND not explicitly
		// disabled (raw-PHP unit harness sets TMDO_FSM_GUARD_DISABLED).
		// Dedicated FSMGuardTest unsets the constant before its own assertions.
		$guard_active = class_exists( 'TMDO_FSM_Guard' )
			&& ! ( defined( 'TMDO_FSM_GUARD_DISABLED' ) && TMDO_FSM_GUARD_DISABLED );
		if ( $guard_active ) {
			$check = TMDO_FSM_Guard::before_transition( $module, $state );
			if ( is_wp_error( $check ) ) {
				return $check;
			}
		}

		$flags            = self::all();
		$flags[ $module ] = $state;
		update_option( self::OPTION_KEY, $flags );
		self::$cache = null; // Invalidate request-level cache.

		// Record entry timestamp (M2) for downstream verify-gate / wash-period checks.
		if ( $guard_active ) {
			TMDO_FSM_Guard::record_entry( $module, $state );
		}

		return true;
	}

	// ── shadow_read_only sub-flag (PR-4) ────────────────────────────────────
	// Orthogonal to the main 7-state FSM. When enabled for a module that is in
	// the `verify` state, every read fans out to BOTH postmeta and the zone
	// table; divergence is logged to wp_wpdo_shadow_diffs without affecting
	// the served value. Lets ops bake confidence before cutover.

	/** Option key storing per-module shadow_read_only flags. */
	private const SHADOW_OPTION_KEY = 'wpdo_features_shadow';

	/**
	 * Request-level cache for shadow flags.
	 *
	 * @var array<string,bool>|null
	 */
	private static ?array $shadow_cache = null;

	/**
	 * Enable shadow_read_only for a module (only meaningful in the verify state).
	 *
	 * @param string $module Module identifier.
	 * @return bool True on success.
	 */
	public static function enable_shadow_read( string $module ): bool {
		$flags            = self::all_shadow();
		$flags[ $module ] = true;
		update_option( self::SHADOW_OPTION_KEY, $flags, false );
		self::$shadow_cache = null;
		return true;
	}

	/**
	 * Disable shadow_read_only for a module.
	 *
	 * @param string $module Module identifier.
	 * @return bool
	 */
	public static function disable_shadow_read( string $module ): bool {
		$flags = self::all_shadow();
		unset( $flags[ $module ] );
		update_option( self::SHADOW_OPTION_KEY, $flags, false );
		self::$shadow_cache = null;
		return true;
	}

	/**
	 * Whether shadow_read_only is currently active for a module.
	 *
	 * Returns true only when:
	 *   - Module is in the `verify` state, AND
	 *   - Shadow flag has been explicitly enabled.
	 *
	 * @param string $module Module identifier.
	 * @return bool
	 */
	public static function is_shadow_read_active( string $module ): bool {
		if ( 'verify' !== self::get( $module ) ) {
			return false;
		}
		$flags = self::all_shadow();
		return ! empty( $flags[ $module ] );
	}

	/**
	 * Return all shadow flags.
	 *
	 * @return array<string,bool>
	 */
	public static function all_shadow(): array {
		if ( null !== self::$shadow_cache ) {
			return self::$shadow_cache;
		}
		$saved = get_option( self::SHADOW_OPTION_KEY, array() );
		if ( ! is_array( $saved ) ) {
			$saved = array();
		}
		self::$shadow_cache = $saved;
		return $saved;
	}

	/**
	 * Check if a module is fully complete (reads and writes on custom table only).
	 *
	 * @param string $module Module identifier.
	 * @return bool True if module state is 'complete'.
	 */
	public static function is_complete( string $module ): bool {
		return 'complete' === self::get( $module );
	}

	/**
	 * Check if dual-write is active for a module.
	 *
	 * @param string $module Module identifier.
	 * @return bool True if module is in a write-active state.
	 */
	public static function is_write_active( string $module ): bool {
		return in_array( self::get( $module ), self::WRITE_ACTIVE_STATES, true );
	}

	/**
	 * Check if reads should come from the custom/zone table.
	 *
	 * @param string $module Module identifier.
	 * @return bool True if module is in a read-custom state.
	 */
	public static function is_read_custom( string $module ): bool {
		return in_array( self::get( $module ), self::READ_CUSTOM_STATES, true );
	}

	/**
	 * Check if query interceptors should be active.
	 *
	 * @param string $module Module identifier.
	 * @return bool True if module is in a query-active state.
	 */
	public static function is_query_active( string $module ): bool {
		return in_array( self::get( $module ), self::QUERY_ACTIVE_STATES, true );
	}

	/**
	 * Reset a module to idle (rollback).
	 *
	 * @param string $module Module identifier.
	 * @return void
	 */
	public static function reset( string $module ): void {
		self::set( $module, 'idle' );
		self::$cache = null; // Invalidate request-level cache.
	}

	/**
	 * Request-level cache for all() to avoid repeated get_option() calls.
	 *
	 * @var array|null
	 */
	private static ?array $cache = null;

	/**
	 * Return all module states.
	 *
	 * @return array<string, string>
	 */
	public static function all(): array {
		if ( null !== self::$cache ) {
			return self::$cache;
		}

		$saved = get_option( self::OPTION_KEY, array() );
		if ( ! is_array( $saved ) ) {
			$saved = array();
		}

		$all_modules = array_merge( self::ADDON_MODULES, self::ZONE_MODULES );
		$defaults    = array_fill_keys( $all_modules, 'idle' );

		self::$cache = array_merge( $defaults, $saved );
		return self::$cache;
	}

	/**
	 * Return only AddOn module states.
	 *
	 * @return array<string, string>
	 */
	public static function addon_modules(): array {
		$all = self::all();
		return array_intersect_key( $all, array_flip( self::ADDON_MODULES ) );
	}

	/**
	 * Return only zone module states.
	 *
	 * @return array<string, string>
	 */
	public static function zone_modules(): array {
		$all = self::all();
		return array_intersect_key( $all, array_flip( self::ZONE_MODULES ) );
	}
}