import { access, mkdir, readFile, stat, writeFile } from 'node:fs/promises';
import { constants } from 'node:fs';
import { join } from 'node:path';
import { listAgentsSnapshot, type AgentSummary } from './agent-config';
import { expandPath, getOpenClawDir } from './paths';

export const AGENT_SYSTEM_DOCUMENTS = [
  {
    kind: 'soul',
    fileName: 'SOUL.md',
  },
  {
    kind: 'identity',
    fileName: 'IDENTITY.md',
  },
  {
    kind: 'user',
    fileName: 'USER.md',
  },
  {
    kind: 'agent',
    fileName: 'AGENTS.md',
  },
  {
    kind: 'tool',
    fileName: 'TOOLS.md',
  },
  {
    kind: 'heartbeat',
    fileName: 'HEARTBEAT.md',
  },
  {
    kind: 'boot',
    fileName: 'BOOT.md',
  },
] as const;

export type AgentSystemDocumentKind = typeof AGENT_SYSTEM_DOCUMENTS[number]['kind'];
export type AgentSystemDocumentSource = 'workspace' | 'template' | 'empty';

export interface AgentSystemDocumentAgent {
  id: string;
  name: string;
  isDefault: boolean;
  workspace: string;
}

export interface AgentSystemDocument {
  kind: AgentSystemDocumentKind;
  fileName: string;
  path: string;
  exists: boolean;
  source: AgentSystemDocumentSource;
  content: string;
  size: number;
  updatedAt: number | null;
  templateAvailable: boolean;
  templatePath: string;
}

export interface AgentSystemDocumentsSnapshot {
  success: true;
  selectedAgentId: string;
  defaultAgentId: string;
  agents: AgentSystemDocumentAgent[];
  documents: AgentSystemDocument[];
  paths: {
    workspace: string;
    templateDir: string;
  };
}

const MAX_DOCUMENT_BYTES = 512 * 1024;

function getDescriptor(kind: string): typeof AGENT_SYSTEM_DOCUMENTS[number] | null {
  return AGENT_SYSTEM_DOCUMENTS.find((document) => document.kind === kind) ?? null;
}

export function isAgentSystemDocumentKind(kind: string): kind is AgentSystemDocumentKind {
  return getDescriptor(kind) !== null;
}

async function fileExists(path: string): Promise<boolean> {
  try {
    await access(path, constants.F_OK);
    return true;
  } catch {
    return false;
  }
}

function resolveTemplateDir(): string {
  return join(getOpenClawDir(), 'docs', 'reference', 'templates');
}

function resolveTemplatePath(fileName: string): string {
  return join(resolveTemplateDir(), fileName);
}

function toDocumentAgent(agent: AgentSummary): AgentSystemDocumentAgent {
  return {
    id: agent.id,
    name: agent.name,
    isDefault: agent.isDefault,
    workspace: agent.workspace,
  };
}

async function resolveAgent(agentId?: string): Promise<{
  selected: AgentSystemDocumentAgent;
  defaultAgentId: string;
  agents: AgentSystemDocumentAgent[];
}> {
  const snapshot = await listAgentsSnapshot();
  const agents = snapshot.agents.map(toDocumentAgent);
  if (agents.length === 0) {
    throw new Error('No OpenClaw agents are configured');
  }

  const requestedAgentId = typeof agentId === 'string' ? agentId.trim() : '';
  const selected = requestedAgentId
    ? agents.find((agent) => agent.id === requestedAgentId)
    : agents.find((agent) => agent.id === snapshot.defaultAgentId) ?? agents[0];

  if (!selected) {
    throw new Error(`Agent "${requestedAgentId}" not found`);
  }

  return {
    selected,
    defaultAgentId: snapshot.defaultAgentId,
    agents,
  };
}

async function readTemplate(fileName: string): Promise<string | null> {
  const templatePath = resolveTemplatePath(fileName);
  if (!(await fileExists(templatePath))) return null;
  return readFile(templatePath, 'utf8');
}

async function readDocument(agent: AgentSystemDocumentAgent, kind: AgentSystemDocumentKind): Promise<AgentSystemDocument> {
  const descriptor = getDescriptor(kind);
  if (!descriptor) {
    throw new Error(`Unsupported system document kind "${kind}"`);
  }

  const workspace = expandPath(agent.workspace);
  const documentPath = join(workspace, descriptor.fileName);
  const templatePath = resolveTemplatePath(descriptor.fileName);
  const template = await readTemplate(descriptor.fileName);

  if (await fileExists(documentPath)) {
    const [content, stats] = await Promise.all([
      readFile(documentPath, 'utf8'),
      stat(documentPath),
    ]);
    return {
      kind,
      fileName: descriptor.fileName,
      path: documentPath,
      exists: true,
      source: 'workspace',
      content,
      size: stats.size,
      updatedAt: stats.mtimeMs,
      templateAvailable: template !== null,
      templatePath,
    };
  }

  const content = template ?? '';
  return {
    kind,
    fileName: descriptor.fileName,
    path: documentPath,
    exists: false,
    source: template === null ? 'empty' : 'template',
    content,
    size: 0,
    updatedAt: null,
    templateAvailable: template !== null,
    templatePath,
  };
}

export async function readAgentSystemDocuments(agentId?: string): Promise<AgentSystemDocumentsSnapshot> {
  const { selected, defaultAgentId, agents } = await resolveAgent(agentId);
  const documents = await Promise.all(
    AGENT_SYSTEM_DOCUMENTS.map((document) => readDocument(selected, document.kind)),
  );
  return {
    success: true,
    selectedAgentId: selected.id,
    defaultAgentId,
    agents,
    documents,
    paths: {
      workspace: expandPath(selected.workspace),
      templateDir: resolveTemplateDir(),
    },
  };
}

export async function saveAgentSystemDocument(
  agentId: string | undefined,
  kind: AgentSystemDocumentKind,
  content: string,
): Promise<AgentSystemDocumentsSnapshot> {
  if (typeof content !== 'string') {
    throw new Error('Document content must be a string');
  }
  const byteLength = Buffer.byteLength(content, 'utf8');
  if (byteLength > MAX_DOCUMENT_BYTES) {
    throw new Error(`Document is too large (${byteLength} bytes, max ${MAX_DOCUMENT_BYTES})`);
  }

  const { selected } = await resolveAgent(agentId);
  const descriptor = getDescriptor(kind);
  if (!descriptor) {
    throw new Error(`Unsupported system document kind "${kind}"`);
  }

  const workspace = expandPath(selected.workspace);
  await mkdir(workspace, { recursive: true });
  await writeFile(join(workspace, descriptor.fileName), content, 'utf8');
  return readAgentSystemDocuments(selected.id);
}

export async function resetAgentSystemDocument(
  agentId: string | undefined,
  kind: AgentSystemDocumentKind,
): Promise<AgentSystemDocumentsSnapshot> {
  const { selected } = await resolveAgent(agentId);
  const descriptor = getDescriptor(kind);
  if (!descriptor) {
    throw new Error(`Unsupported system document kind "${kind}"`);
  }

  const template = await readTemplate(descriptor.fileName);
  if (template === null) {
    throw new Error(`Template for ${descriptor.fileName} is not available`);
  }

  const workspace = expandPath(selected.workspace);
  await mkdir(workspace, { recursive: true });
  await writeFile(join(workspace, descriptor.fileName), template, 'utf8');
  return readAgentSystemDocuments(selected.id);
}