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

/**
 * Asterion Projection — Board #30
 *
 * Asterion's website-facing query surface, separate from Sara.
 *
 * Sara interprets. Asterion verifies. Two distinct surfaces, same source.
 *
 * Asterion responses are:
 *   - grounded in the canonical MD spec corpus (Archvie/sa-core/docs/specs/)
 *   - cite specific files (and excerpts) by name
 *   - refuse to speculate beyond the source
 *   - return "no canonical reference found" when corpus does not contain the answer
 *
 * No write capability anywhere. Read-only by construction.
 *
 * Architecture:
 *   - REST endpoint /sa-orch/v1/asterion/query
 *   - Keyword search across spec corpus + LLM-framed citation answer
 *   - Reuses SA_Orch_Asterion_Explorer::spec_root() and validate_relative_path()
 *   - Reuses LLM provider stack (SA_Orch_LLM_Settings, wp_remote_post)
 *   - Reuses wp_sa_token_log (Board #16) for usage accounting
 *   - Distinct system prompt (librarian role; structurally different shape from Sara)
 *
 * Front-end: assets/asterion-bubble.js + assets/asterion-bubble.css (separate
 * floating button, top-right, distinct visual identity from Sara).
 */
class SA_Orch_Asterion_Projection {

    const HANDLE_JS  = 'sa-orch-asterion-bubble';
    const HANDLE_CSS = 'sa-orch-asterion-bubble';
    const REQUEST_TIMEOUT = 30;

    /** Number of excerpts to return from corpus search. */
    const TOP_K = 5;

    /** Max chars per excerpt window included in the LLM prompt.
     *  Wide enough to give the LLM real context around the match — file headers and
     *  one-paragraph blurbs aren't enough to ground a Truth-Class-style answer. */
    const EXCERPT_CHARS = 1800;

    /* -------------------- Hooks -------------------- */

    public static function register_hooks() {
        add_action( 'admin_enqueue_scripts', [ __CLASS__, 'maybe_enqueue' ] );
    }

    public static function register_routes() {
        register_rest_route( 'sa-orch/v1', '/asterion/query', [
            'methods'             => 'POST',
            'callback'            => [ __CLASS__, 'rest_query' ],
            'permission_callback' => function () {
                return current_user_can( 'manage_options' );
            },
            'args' => [
                'query'         => [ 'type' => 'string', 'required' => true ],
                'asterion_file' => [ 'type' => 'string', 'required' => false ],
            ],
        ] );
    }

    public static function maybe_enqueue( $hook ) {
        if ( ! current_user_can( 'manage_options' ) ) return;

        $page = isset( $_GET['page'] ) ? sanitize_text_field( wp_unslash( $_GET['page'] ) ) : '';

        // Asterion bubble: any SA-Orchestration admin page (the Explorer is a subpage,
        // but Asterion is also useful from Demand Trace / Acceptance Events).
        if ( strpos( $page, 'sa-orchestration' ) !== 0 ) return;

        wp_enqueue_style(
            self::HANDLE_CSS,
            SA_ORCH_URL . 'assets/asterion-bubble.css',
            [],
            SA_ORCH_VERSION
        );

        wp_enqueue_script(
            self::HANDLE_JS,
            SA_ORCH_URL . 'assets/asterion-bubble.js',
            [],
            SA_ORCH_VERSION,
            true
        );

        wp_localize_script( self::HANDLE_JS, 'SA_ORCH_ASTERION', [
            'rest_url' => esc_url_raw( rest_url( 'sa-orch/v1/asterion/query' ) ),
            'nonce'    => wp_create_nonce( 'wp_rest' ),
            'page'     => $page,
        ] );
    }

    /* -------------------- REST handler -------------------- */

    public static function rest_query( WP_REST_Request $request ) {
        $query         = (string) $request->get_param( 'query' );
        $asterion_file = sanitize_text_field( (string) $request->get_param( 'asterion_file' ) );

        if ( trim( $query ) === '' ) {
            return new WP_REST_Response( [
                'error'   => 'empty_query',
                'message' => 'query is required',
            ], 400 );
        }

        $result = self::query( $query, $asterion_file );
        if ( is_wp_error( $result ) ) {
            return new WP_REST_Response( [
                'error'   => $result->get_error_code(),
                'message' => $result->get_error_message(),
            ], 502 );
        }

        return new WP_REST_Response( $result, 200 );
    }

    /* -------------------- Core query -------------------- */

    /**
     * Run a corpus query and return a structured Asterion response.
     *
     * Response shape:
     *   {
     *     answer:    string,    // citation-grounded answer or "no canonical reference found"
     *     citations: array,     // [{ file, excerpt }, ...]
     *     scope:     string,    // "single_file:<rel>" | "spec_corpus" | "no_corpus"
     *     usage:     array|null,
     *     log_id:    int|null
     *   }
     */
    public static function query( string $query, string $asterion_file = '' ) {
        if ( ! class_exists( 'SA_Orch_Asterion_Explorer' ) ) {
            return new WP_Error( 'no_corpus', 'Asterion Explorer not loaded.' );
        }

        $root = SA_Orch_Asterion_Explorer::spec_root();
        if ( ! is_dir( $root ) ) {
            return [
                'answer'    => 'no canonical reference found in the spec corpus (corpus root unreachable)',
                'citations' => [],
                'scope'     => 'no_corpus',
                'usage'     => null,
                'log_id'    => null,
            ];
        }

        // Determine search scope.
        $scope    = 'spec_corpus';
        $bound_md = null;
        if ( $asterion_file !== '' ) {
            $resolved = SA_Orch_Asterion_Explorer::validate_relative_path( $asterion_file );
            if ( is_array( $resolved ) ) {
                $bound_md = $resolved;
                $scope    = 'single_file:' . $resolved['relative'];
            }
        }

        // Retrieve excerpts.
        $excerpts = $bound_md
            ? self::search_single_file( $bound_md['absolute'], $bound_md['relative'], $query )
            : self::search_corpus( $root, $query );

        // No matches → refuse to speculate.
        if ( empty( $excerpts ) ) {
            return [
                'answer'    => 'no canonical reference found in the spec corpus',
                'citations' => [],
                'scope'     => $scope,
                'usage'     => null,
                'log_id'    => null,
            ];
        }

        // Frame with LLM (Model B). If LLM is disabled or fails, fall through
        // to raw-excerpt mode so the surface still works.
        $framed = self::frame_with_llm( $query, $excerpts, $scope );
        if ( is_array( $framed ) ) {
            return $framed + [
                'citations' => $excerpts,
                'scope'     => $scope,
            ];
        }

        // Fallback: raw excerpts as the "answer" when LLM unavailable.
        $answer_lines = [ 'Citation-only mode (LLM unavailable). Raw excerpts:' ];
        foreach ( $excerpts as $i => $ex ) {
            $answer_lines[] = sprintf( '[%d] %s', $i + 1, $ex['file'] );
        }
        return [
            'answer'    => implode( "\n", $answer_lines ),
            'citations' => $excerpts,
            'scope'     => $scope,
            'usage'     => null,
            'log_id'    => null,
        ];
    }

    /* -------------------- Search -------------------- */

    /**
     * Search the entire spec corpus for terms in $query.
     * Returns up to TOP_K excerpts ranked by hit score.
     */
    private static function search_corpus( string $root, string $query ): array {
        $terms = self::extract_terms( $query );
        if ( empty( $terms ) ) return [];

        $hits = [];
        self::walk_corpus( $root, '', function ( $abs, $rel ) use ( $terms, &$hits ) {
            $content = @file_get_contents( $abs );
            if ( $content === false ) return;
            $score = 0;
            foreach ( $terms as $t ) {
                $score += substr_count( strtolower( $content ), $t );
            }
            if ( $score > 0 ) {
                $hits[] = [
                    'file'    => $rel,
                    'score'   => $score,
                    'excerpt' => self::best_excerpt( $content, $terms ),
                ];
            }
        } );

        usort( $hits, function ( $a, $b ) { return $b['score'] - $a['score']; } );
        $hits = array_slice( $hits, 0, self::TOP_K );

        $out = [];
        foreach ( $hits as $h ) {
            $out[] = [ 'file' => $h['file'], 'excerpt' => $h['excerpt'] ];
        }
        return $out;
    }

    /**
     * Search a single bound MD file.
     */
    private static function search_single_file( string $abs, string $rel, string $query ): array {
        $content = @file_get_contents( $abs );
        if ( $content === false ) return [];

        $terms = self::extract_terms( $query );
        if ( empty( $terms ) ) return [];

        $score = 0;
        foreach ( $terms as $t ) {
            $score += substr_count( strtolower( $content ), $t );
        }
        if ( $score === 0 ) return [];

        return [ [
            'file'    => $rel,
            'excerpt' => self::best_excerpt( $content, $terms ),
        ] ];
    }

    private static function walk_corpus( string $abs, string $rel_prefix, callable $cb ) {
        $entries = @scandir( $abs );
        if ( $entries === false ) return;
        foreach ( $entries as $e ) {
            if ( $e === '.' || $e === '..' ) continue;
            $a = $abs . '/' . $e;
            $r = $rel_prefix === '' ? $e : $rel_prefix . '/' . $e;
            if ( is_dir( $a ) ) {
                self::walk_corpus( $a, $r, $cb );
            } elseif ( is_file( $a ) && substr( strtolower( $e ), -3 ) === '.md' ) {
                $cb( $a, $r );
            }
        }
    }

    /**
     * Extract lowercased search terms from the query.
     * Strips stopwords/punctuation; minimum 3-char tokens.
     */
    private static function extract_terms( string $query ): array {
        $q = strtolower( $query );
        $q = preg_replace( '/[^a-z0-9_\-\s]/', ' ', $q );
        $tokens = preg_split( '/\s+/', $q, -1, PREG_SPLIT_NO_EMPTY );
        $stop = [ 'the','and','but','for','are','was','were','have','has','had','will',
                  'with','this','that','from','what','which','about','they','them',
                  'their','our','your','his','her','its','some','any','all','can',
                  'how','why','when','where','who','whom','does','did','done','not',
                  'into','onto','off','out','only','also','each','more','less','very',
                  'such','than','then','than','these','those','say','says','said' ];
        $out = [];
        foreach ( $tokens as $t ) {
            if ( strlen( $t ) < 3 ) continue;
            if ( in_array( $t, $stop, true ) ) continue;
            $out[ $t ] = true;
        }
        return array_keys( $out );
    }

    /**
     * Find the best excerpt window in $content given $terms.
     *
     * Strategy: pick the position with the highest local term-density across a
     * sliding window — not just the first match. File headers and credit blurbs
     * often contain isolated keyword hits; the actual definition is further down.
     * Windowing on density beats first-match for citation quality.
     */
    private static function best_excerpt( string $content, array $terms ): string {
        $lower    = strtolower( $content );
        $len      = strlen( $lower );
        if ( $len === 0 ) return '';

        // Collect all match positions for any term.
        $positions = [];
        foreach ( $terms as $t ) {
            $off = 0;
            while ( ( $p = strpos( $lower, $t, $off ) ) !== false ) {
                $positions[] = $p;
                $off = $p + max( 1, strlen( $t ) );
            }
        }
        if ( empty( $positions ) ) {
            // No match — fall back to first chars
            return function_exists( 'mb_substr' )
                ? mb_substr( $content, 0, self::EXCERPT_CHARS )
                : substr( $content, 0, self::EXCERPT_CHARS );
        }
        sort( $positions );

        // Slide a window across positions; pick the position whose window
        // contains the most match positions (density).
        $window = self::EXCERPT_CHARS;
        $best_pos   = $positions[0];
        $best_count = 0;
        foreach ( $positions as $p ) {
            $count = 0;
            foreach ( $positions as $q ) {
                if ( $q >= $p && $q < $p + $window ) $count++;
                if ( $q >= $p + $window ) break;
            }
            if ( $count > $best_count ) {
                $best_count = $count;
                $best_pos   = $p;
            }
        }

        // Center window on best_pos (back off slightly so match isn't at edge)
        $half  = (int) ( $window / 4 ); // back off 25%, not 50% — anchor near top of window
        $start = max( 0, $best_pos - $half );
        $exc   = function_exists( 'mb_substr' )
            ? mb_substr( $content, $start, $window )
            : substr( $content, $start, $window );
        if ( $start > 0 )                       $exc = '… ' . $exc;
        if ( $start + $window < strlen( $content ) ) $exc .= ' …';
        return $exc;
    }

    /* -------------------- LLM framing -------------------- */

    /**
     * Frame the excerpts as a librarian-tone, citation-grounded answer.
     * Returns array { answer, usage, log_id } on success, null on failure.
     */
    private static function frame_with_llm( string $query, array $excerpts, string $scope ) {
        if ( ! class_exists( 'SA_Orch_LLM_Settings' ) ) return null;
        $settings = SA_Orch_LLM_Settings::get();
        if ( empty( $settings['enabled'] ) || empty( $settings['api_token'] )
             || empty( $settings['api_base_url'] ) || empty( $settings['model'] ) ) {
            return null;
        }

        $url = rtrim( (string) $settings['api_base_url'], '/' ) . '/chat/completions';

        $excerpt_block = "Excerpts retrieved from the spec corpus (verbatim; do not invent beyond these):\n\n";
        foreach ( $excerpts as $i => $ex ) {
            $n = $i + 1;
            $excerpt_block .= "[CITATION {$n}] file: {$ex['file']}\n";
            $excerpt_block .= "----\n";
            $excerpt_block .= $ex['excerpt'] . "\n";
            $excerpt_block .= "----\n\n";
        }

        $messages = [
            [ 'role' => 'system', 'content' => self::system_prompt() ],
            [ 'role' => 'user',   'content' => $excerpt_block . "User question:\n\n" . $query ],
        ];

        $payload = [
            'model'           => (string) $settings['model'],
            'messages'        => $messages,
            'response_format' => [ 'type' => 'json_object' ],
            'temperature'     => 0.1,
        ];

        $response = wp_remote_post( $url, [
            'headers' => [
                'Authorization' => 'Bearer ' . (string) $settings['api_token'],
                'Content-Type'  => 'application/json',
            ],
            'body'    => wp_json_encode( $payload ),
            'timeout' => self::REQUEST_TIMEOUT,
        ] );

        if ( is_wp_error( $response ) ) return null;
        $code = (int) wp_remote_retrieve_response_code( $response );
        if ( $code < 200 || $code >= 300 ) return null;

        $body     = (string) wp_remote_retrieve_body( $response );
        $envelope = json_decode( $body, true );
        if ( ! is_array( $envelope ) || ! isset( $envelope['choices'][0]['message']['content'] ) ) return null;

        $content = (string) $envelope['choices'][0]['message']['content'];
        $parsed  = json_decode( $content, true );
        if ( ! is_array( $parsed ) ) return null;

        $answer = isset( $parsed['answer'] ) ? (string) $parsed['answer'] : '';
        if ( $answer === '' ) {
            $answer = 'no canonical reference found in the spec corpus';
        }

        // Token log
        $usage  = isset( $envelope['usage'] ) && is_array( $envelope['usage'] ) ? $envelope['usage'] : null;
        $log_id = null;
        if ( $usage !== null && class_exists( 'SA_Orch_Token_Log' ) ) {
            $log_id = SA_Orch_Token_Log::record(
                'asterion',
                (string) $settings['model'],
                $usage,
                (int) get_current_user_id()
            );
            $log_id = $log_id > 0 ? $log_id : null;
        }

        return [
            'answer' => $answer,
            'usage'  => $usage,
            'log_id' => $log_id,
        ];
    }

    /**
     * Asterion's system prompt — librarian role.
     * Structurally distinct from Sara's prompt:
     *   - no interpretation tone, no synthesis, no advice
     *   - citation-grounded, refusal-to-speculate, file-named
     *   - returns { answer: string } JSON; no summary/suggestion/draft/notes
     */
    public static function system_prompt(): string {
        return "ASTERION — canonical librarian for the SA-Core spec corpus.\n"
             . "\n"
             . "You are NOT Sara. You are NOT an interpreter. You are NOT an advisor.\n"
             . "You are the verifier: a strict, citation-grounded surface over\n"
             . "Archvie/sa-core/docs/specs/. Your job is to ground every claim in\n"
             . "specific source excerpts that have been provided to you, and to\n"
             . "refuse if the answer is not present in those excerpts.\n"
             . "\n"
             . "TONE\n"
             . "  - Direct. Citation-led. No interpretive framing. No synthesis tone.\n"
             . "  - No \"I think\", no \"likely\", no \"probably\", no advisory voice.\n"
             . "  - Reference the corpus by file name + section. Use phrases like\n"
             . "    \"per 02-invariants.md, I2 ...\" — name the file and the labeled\n"
             . "    element.\n"
             . "\n"
             . "OUTPUT (strict JSON; no other keys)\n"
             . "  { \"answer\": string }\n"
             . "\n"
             . "RULES\n"
             . "  - If the excerpts contain the answer: state it directly and cite the\n"
             . "    file(s) and labeled elements (I1, I2, R-O-1, named sections). Quote\n"
             . "    short phrases verbatim where it adds verifiability.\n"
             . "  - If the excerpts do NOT contain the answer (the question is off-topic,\n"
             . "    or the corpus is silent): set answer to exactly:\n"
             . "      \"no canonical reference found in the spec corpus\"\n"
             . "    Do not speculate. Do not extrapolate. Do not invent.\n"
             . "  - You may NOT introduce concepts not present in the excerpts.\n"
             . "  - You may NOT advise the user on what to do.\n"
             . "  - You may NOT use Sara's structured 4-key shape. Only { \"answer\" }.\n"
             . "\n"
             . "Sara interprets. You verify. The Human arbitrates.\n";
    }
}