<?php
defined( 'ABSPATH' ) || exit;

class SA_Orch_Arbitration {

    /**
     * Write an arbitration record + optional plan_link rows.
     *
     * Required:
     *   - demand_surface  (string)  e.g. 'fluent-support'
     *   - demand_ref      (string)  e.g. 'ticket#12'
     *   - rationale       (non-empty string)
     *   - projection_type (string)  e.g. 'scope-direct-no-plan'
     *
     * Optional:
     *   - actor_user_id  (int; default current user)
     *   - correlation_id (string; default UUID v4)
     *   - causation_id   (string|null)
     *   - truth_class    (string; default 'canonical')
     *   - plan_refs      (array of [ surface, ref, link_kind? ])
     *
     * Returns array on success, WP_Error on failure.
     */
    public static function write( array $args ) {
        global $wpdb;

        $demand_surface  = isset( $args['demand_surface'] )  ? trim( (string) $args['demand_surface'] )  : '';
        $demand_ref      = isset( $args['demand_ref'] )      ? trim( (string) $args['demand_ref'] )      : '';
        $rationale       = isset( $args['rationale'] )       ? trim( (string) $args['rationale'] )       : '';
        $projection_type = isset( $args['projection_type'] ) ? trim( (string) $args['projection_type'] ) : '';

        if ( $demand_surface === '' || $demand_ref === '' ) {
            return new WP_Error( 'missing_demand', 'demand_surface and demand_ref are required' );
        }
        if ( $rationale === '' ) {
            return new WP_Error( 'missing_rationale', 'rationale is required (mandatory per SARA discipline)' );
        }
        if ( $projection_type === '' ) {
            return new WP_Error( 'missing_projection_type', 'projection_type is required' );
        }
        if ( ! in_array( $demand_surface, SA_Orch_Bridge_Fluent::known_surfaces(), true ) ) {
            return new WP_Error( 'unknown_surface', "demand_surface '$demand_surface' is not in known surface vocabulary" );
        }
        if ( ! SA_Orch_Bridge_Fluent::validate( $demand_surface, $demand_ref ) ) {
            return new WP_Error( 'invalid_demand_ref', "demand_ref does not resolve: {$demand_surface}/{$demand_ref}" );
        }

        $actor_user_id = isset( $args['actor_user_id'] ) ? (int) $args['actor_user_id'] : get_current_user_id();
        if ( $actor_user_id === 0 ) { $actor_user_id = null; }

        $correlation_id = isset( $args['correlation_id'] ) && $args['correlation_id'] !== ''
            ? (string) $args['correlation_id']
            : wp_generate_uuid4();
        $causation_id   = isset( $args['causation_id'] ) && $args['causation_id'] !== ''
            ? (string) $args['causation_id']
            : null;
        $truth_class    = isset( $args['truth_class'] ) && $args['truth_class'] !== ''
            ? (string) $args['truth_class']
            : 'canonical';

        $plan_refs = isset( $args['plan_refs'] ) && is_array( $args['plan_refs'] ) ? $args['plan_refs'] : [];

        // Validate plan_refs each
        foreach ( $plan_refs as $i => $pr ) {
            $ps  = isset( $pr['surface'] ) ? trim( (string) $pr['surface'] ) : '';
            $prr = isset( $pr['ref'] )     ? trim( (string) $pr['ref'] )     : '';
            if ( $ps === '' || $prr === '' ) {
                return new WP_Error( 'invalid_plan_ref', "plan_refs[$i] missing surface or ref" );
            }
            if ( ! in_array( $ps, SA_Orch_Bridge_Fluent::known_surfaces(), true ) ) {
                return new WP_Error( 'unknown_surface', "plan_refs[$i].surface '$ps' is not known" );
            }
            if ( ! SA_Orch_Bridge_Fluent::validate( $ps, $prr ) ) {
                return new WP_Error( 'invalid_plan_ref', "plan_refs[$i] does not resolve: $ps/$prr" );
            }
        }

        $created_at = current_time( 'mysql', true );
        $hash       = self::compute_hash( $demand_surface, $demand_ref, $created_at, $actor_user_id, $correlation_id );

        // Asterion-first: ledger entry written before any DB row.
        $frontmatter = [
            'kind'            => 'arbitration',
            'hash'            => $hash,
            'demand_surface'  => $demand_surface,
            'demand_ref'      => $demand_ref,
            'projection_type' => $projection_type,
            'actor_user_id'   => $actor_user_id,
            'correlation_id'  => $correlation_id,
            'causation_id'    => $causation_id,
            'truth_class'     => $truth_class,
            'plan_refs'       => array_map( function ( $pr ) {
                return ( $pr['surface'] ?? '' ) . ':' . ( $pr['ref'] ?? '' );
            }, $plan_refs ),
            'created_at'      => $created_at,
        ];

        $body = "## Rationale\n\n" . $rationale . "\n";

        $rel_path = SA_Orch_Asterion::write( 'arbitration', $hash, $frontmatter, $body );
        if ( is_wp_error( $rel_path ) ) {
            return $rel_path;
        }

        // Now insert the runtime cache row.
        $table = $wpdb->prefix . SA_ORCH_DB_PREFIX . 'arbitration';
        $ok = $wpdb->insert( $table, [
            'hash'            => $hash,
            'demand_surface'  => $demand_surface,
            'demand_ref'      => $demand_ref,
            'rationale'       => $rationale,
            'projection_type' => $projection_type,
            'actor_user_id'   => $actor_user_id,
            'correlation_id'  => $correlation_id,
            'causation_id'    => $causation_id,
            'truth_class'     => $truth_class,
            'asterion_path'   => $rel_path,
            'created_at'      => $created_at,
        ] );

        if ( $ok === false ) {
            return new WP_Error( 'db_insert_failed', $wpdb->last_error, [ 'asterion_path' => $rel_path ] );
        }

        $arbitration_id = (int) $wpdb->insert_id;

        $link_ids = [];
        foreach ( $plan_refs as $pr ) {
            $link_id = SA_Orch_Link::write( [
                'arbitration_id' => $arbitration_id,
                'plan_surface'   => $pr['surface'],
                'plan_ref'       => $pr['ref'],
                'link_kind'      => $pr['link_kind'] ?? 'derived',
            ] );
            if ( is_wp_error( $link_id ) ) {
                return $link_id;
            }
            $link_ids[] = $link_id;
        }

        // v0.6.0: notify projection / side-effect listeners. Decoupled — listeners
        // (e.g. SA_Orch_Projection_Fluent_Support) react via WordPress action hooks.
        do_action( 'sa_orch_arbitration_written', [
            'id'              => $arbitration_id,
            'hash'            => $hash,
            'demand_surface'  => $demand_surface,
            'demand_ref'      => $demand_ref,
            'projection_type' => $projection_type,
            'truth_class'     => $truth_class,
            'plan_link_ids'   => $link_ids,
            'correlation_id'  => $correlation_id,
            'asterion_path'   => $rel_path,
        ] );

        return [
            'id'             => $arbitration_id,
            'hash'           => $hash,
            'asterion_path'  => $rel_path,
            'plan_link_ids'  => $link_ids,
            'correlation_id' => $correlation_id,
        ];
    }

    private static function compute_hash( $demand_surface, $demand_ref, $created_at, $actor_user_id, $correlation_id ) {
        $material = implode( '|', [
            $demand_surface,
            $demand_ref,
            $created_at,
            (int) $actor_user_id,
            $correlation_id,
        ] );
        return substr( hash( 'sha256', $material ), 0, 32 );
    }
}