// kbblock.ts — TypeScript mirror of HarborForge.PlexumPlugin's
// internal/kbblock package. Per-session storage of HarborForge KB
// facts the agent has cached, rendered as <kb-fact id=N kb=<code>
// source=topic:<slug>>content</kb-fact> per DESIGN-DYNAMIC-BLOCK.md
// §3.3 / §4.4.
//
// Storage location:
//
//   <OPENCLAW_PATH>/agents/<agentId>/sessions/<sessionId>/plugins/
//   harbor-forge/kb-block.json
//
// Fade NOT applied in v1 (§9 #3 placeholder; defer until prod data).
// Cross-runtime aligned with Plexum kbblock.

import * as fs from 'node:fs';
import * as os from 'node:os';
import * as path from 'node:path';

export interface Entry {
  id: number;          // HF backend DB primary key
  kb_code: string;     // e.g. "KB-PAYROT"
  source_topic: string; // human slug from HF, e.g. "debugging"
  content: string;
  insert_seq: number;
  added_at_turn: number;
  last_refresh_at_turn: number;
}

interface BlockShape {
  version: number;
  next_seq: number;
  entries: Entry[];
}

const FILE_NAME = 'kb-block.json';
const VERSION = 1;

function openclawRoot(): string {
  const env = process.env.OPENCLAW_PATH;
  if (env) return env;
  const home = process.env.HOME || os.homedir();
  return path.join(home, '.openclaw');
}

/** sessions/<sid>/plugins/harbor-forge path under openclaw profile. */
export function sessionDir(agentId: string, sessionId: string): string {
  return path.join(openclawRoot(), 'agents', agentId, 'sessions', sessionId, 'plugins', 'harbor-forge');
}

export function blockPath(agentId: string, sessionId: string): string {
  return path.join(sessionDir(agentId, sessionId), FILE_NAME);
}

/** Block is the in-memory representation. Cheap to Open + Save per call. */
export class Block {
  private readonly path: string;
  next_seq: number = 1;
  entries: Entry[] = [];

  private constructor(blockPath: string) { this.path = blockPath; }

  /** Open from disk (missing file → empty block). Throws on parse error. */
  static open(agentId: string, sessionId: string): Block {
    if (!agentId || !sessionId) {
      throw new Error('kbblock.open: agentId + sessionId required');
    }
    const b = new Block(blockPath(agentId, sessionId));
    try {
      const raw = fs.readFileSync(b.path, 'utf8');
      if (raw.trim().length === 0) return b;
      const data = JSON.parse(raw) as Partial<BlockShape>;
      if (data.next_seq && data.next_seq > 0) b.next_seq = data.next_seq;
      if (Array.isArray(data.entries)) b.entries = data.entries;
    } catch (err: any) {
      if (err?.code === 'ENOENT') return b;
      throw err;
    }
    return b;
  }

  len(): number { return this.entries.length; }

  has(id: number): boolean {
    return this.entries.some((e) => e.id === id);
  }

  /** Add new entry. Returns it; null on duplicate (silent no-op per §9 #4). */
  add(id: number, kb_code: string, source_topic: string, content: string, at_turn: number): Entry | null {
    if (this.has(id)) return null;
    const e: Entry = {
      id, kb_code, source_topic, content,
      insert_seq: this.next_seq,
      added_at_turn: at_turn,
      last_refresh_at_turn: at_turn,
    };
    this.next_seq += 1;
    this.entries.push(e);
    return e;
  }

  /** Remove given IDs. Returns IDs actually removed. */
  remove(ids: number[]): number[] {
    const want = new Set(ids);
    const removed: number[] = [];
    this.entries = this.entries.filter((e) => {
      if (want.has(e.id)) {
        removed.push(e.id);
        return false;
      }
      return true;
    });
    return removed;
  }

  lookup(id: number): Entry | undefined {
    return this.entries.find((e) => e.id === id);
  }

  /** Atomic save (tmp+rename, 0600). Empty block with no prior file = no-op. */
  save(): void {
    if (this.entries.length === 0) {
      if (!fs.existsSync(this.path)) return;
    }
    fs.mkdirSync(path.dirname(this.path), { recursive: true });
    const payload: BlockShape = {
      version: VERSION,
      next_seq: this.next_seq,
      entries: this.entries,
    };
    const tmp = this.path + '.tmp';
    fs.writeFileSync(tmp, JSON.stringify(payload, null, 2), { mode: 0o600 });
    fs.renameSync(tmp, this.path);
  }

  /**
   * Render the <kb-block> inner body — flat sequence of
   * <kb-fact id=N kb=<code> source=topic:<slug>>content</kb-fact>
   * ordered by insert_seq (§9 #4). Empty block → "".
   */
  render(): string {
    if (this.entries.length === 0) return '';
    const ordered = [...this.entries].sort((a, b) => a.insert_seq - b.insert_seq);
    const lines: string[] = [];
    ordered.forEach((e, i) => {
      if (i > 0) lines.push('');
      let head = `<kb-fact id=${e.id} kb=${e.kb_code}`;
      if (e.source_topic) head += ` source=topic:${e.source_topic}`;
      head += '>';
      lines.push(head);
      lines.push(e.content);
      lines.push('</kb-fact>');
    });
    return lines.join('\n') + '\n';
  }
}