/**
 * Markdown file–backed `MemoryRepository`. Each memory is a `.md` file with
 * YAML-ish frontmatter. Mirrors `apps/infrastructure/src/persistence/cms/memory_repo.rs`.
 */
import * as fs from "node:fs";
import * as path from "node:path";
import { type Memory, type MemoryRepository, memoryPath } from "@zesdex/domain";
import { randomUUID } from "node:crypto";

/** Escape newlines so they do not break line-oriented frontmatter. */
function escapeNewlines(s: string): string {
  return s.replace(/\n/g, "\\n");
}
function unescapeNewlines(s: string): string {
  return s.replace(/\\n/g, "\n");
}

function buildFrontmatter(memory: Memory): string {
  const outcome = memory.outcome ? `outcome: ${escapeNewlines(memory.outcome)}\n` : "";
  const scope = memory.scope ? `scope: ${escapeNewlines(memory.scope)}\n` : "";
  const before = memory.before_snippet ? `before: ${escapeNewlines(memory.before_snippet)}\n` : "";
  const after = memory.after_snippet ? `after: ${escapeNewlines(memory.after_snippet)}\n` : "";
  const prov = memory.provenances.length > 0 ? `provenances: ${memory.provenances.join(", ")}\n` : "";
  return `name: ${memory.name}\ndescription: ${memory.description}\nkind: ${memory.kind}\ncreated_at: ${memory.created_at}\nupdated_at: ${memory.updated_at}\nlifecycle: ${memory.lifecycle}\n${outcome}${scope}${before}${after}${prov}`;
}

function parseFrontmatter(front: string): Record<string, string> {
  const map: Record<string, string> = {};
  for (const line of front.split("\n")) {
    const idx = line.indexOf(":");
    if (idx === -1) continue;
    map[line.slice(0, idx).trim()] = line.slice(idx + 1).trim();
  }
  return map;
}

function parseMemory(content: string): Memory {
  let body = content;
  if (body.startsWith("---\n")) body = body.slice(4);
  const parts = body.split("\n---\n", 2);
  const frontPart = parts[0];
  const mdPart = parts[1];
  if (frontPart === undefined || mdPart === undefined) throw new Error("missing frontmatter");
  const front = parseFrontmatter(frontPart);
  const md = mdPart.trim();

  const prov = front.provenances ?? "";
  return {
    name: front.name ?? "",
    description: front.description ?? "",
    content: md,
    kind: front.kind ?? "reference",
    created_at: Number(front.created_at) || 0,
    updated_at: Number(front.updated_at) || 0,
    outcome: front.outcome ? unescapeNewlines(front.outcome) : undefined,
    lifecycle: front.lifecycle ?? "new",
    scope: front.scope ? unescapeNewlines(front.scope) : undefined,
    before_snippet: front.before ? unescapeNewlines(front.before) : undefined,
    after_snippet: front.after ? unescapeNewlines(front.after) : undefined,
    provenances: prov === "" ? [] : prov.split(", "),
  };
}

/** File-based `MemoryRepository` storing memories as `.md` files. */
export class MarkdownMemoryRepository implements MemoryRepository {
  async list(memoryDir: string): Promise<string[]> {
    let entries: string[];
    try {
      entries = fs.readdirSync(memoryDir);
    } catch {
      return [];
    }
    return entries
      .filter((n) => n.endsWith(".md") && n !== "MEMORY.md")
      .map((n) => n.slice(0, -3));
  }

  async load(memoryDir: string, name: string): Promise<Memory> {
    const file = memoryPath(memoryDir, name);
    const content = fs.readFileSync(file, "utf8");
    try {
      return parseMemory(content);
    } catch (e) {
      throw new Error(`failed to parse memory '${name}': ${(e as Error).message}`);
    }
  }

  async save(memoryDir: string, memory: Memory): Promise<void> {
    const file = memoryPath(memoryDir, memory.name);
    fs.mkdirSync(path.dirname(file), { recursive: true });
    const content = `---\n${buildFrontmatter(memory)}---\n\n${memory.content}`;
    const tmp = path.join(path.dirname(file), `.${randomUUID()}.tmp`);
    const fd = fs.openSync(tmp, "w");
    try {
      fs.writeFileSync(fd, content);
      fs.fsyncSync(fd);
    } finally {
      fs.closeSync(fd);
    }
    fs.renameSync(tmp, file);
  }

  async delete(memoryDir: string, name: string): Promise<void> {
    const file = memoryPath(memoryDir, name);
    if (fs.existsSync(file)) fs.unlinkSync(file);
  }
}