import { createHash, randomUUID } from 'node:crypto';
import { chmod, lstat, mkdir, readFile, rename, unlink, writeFile } from 'node:fs/promises';
import { homedir } from 'node:os';
import { dirname, join, resolve } from 'node:path';
import { compareCodePoints } from './deterministic-order.js';

export type AgentEnvironmentKind = 'generated' | 'local';

export interface AgentEnvironmentDiagnostic {
  readonly code: string;
  readonly key: string;
  readonly sha256: string;
}

export interface AgentEnvironmentProjectionOptions {
  readonly mosaicHome: string;
  readonly agentEnvDir: string;
  readonly agentName: string;
  readonly generated: Readonly<Record<string, string>>;
}

export interface AgentGeneratedProjectionDeletionOptions {
  readonly mosaicHome: string;
  readonly agentEnvDir: string;
  readonly agentName: string;
}

export interface AgentEnvironmentProjectionResult {
  readonly generatedPath: string;
  readonly localPath: string;
  readonly quarantinePath?: string;
  readonly diagnostics: readonly AgentEnvironmentDiagnostic[];
}

/** Sanitized, non-mutating projection evidence safe for migration output. */
export interface AgentEnvironmentProjectionPreview {
  readonly agentName: string;
  readonly generated: 'rebuild';
  readonly legacy: 'absent' | 'regenerate-only' | 'relocate-local' | 'quarantine';
  readonly relocatedKeys: readonly string[];
  readonly diagnostics: readonly AgentEnvironmentDiagnostic[];
}

/** A projection fully validated without changing managed files. */
export interface PreparedAgentEnvironmentProjection {
  readonly mosaicHome: string;
  readonly agentEnvDir: string;
  readonly generatedPath: string;
  readonly localPath: string;
  readonly legacyPath: string;
  readonly generated: string;
  readonly local: string;
  readonly legacy?: string;
  readonly legacyRelocatedKeys: readonly string[];
  readonly quarantinePath?: string;
  readonly diagnostics: readonly AgentEnvironmentDiagnostic[];
}

export class AgentEnvBoundaryError extends Error {
  readonly diagnostic: AgentEnvironmentDiagnostic;

  constructor(code: string, key: string, value: string) {
    const diagnostic: AgentEnvironmentDiagnostic = {
      code,
      key,
      sha256: hashValue(value),
    };
    super(`Agent environment rejected: code=${code} key=${key} sha256=${diagnostic.sha256}`);
    this.name = 'AgentEnvBoundaryError';
    this.diagnostic = diagnostic;
  }
}

export const GENERATED_AGENT_ENV_KEYS = [
  'MOSAIC_AGENT_NAME',
  'MOSAIC_AGENT_CLASS',
  'MOSAIC_AGENT_RUNTIME',
  'MOSAIC_AGENT_MODEL',
  'MOSAIC_AGENT_REASONING',
  'MOSAIC_AGENT_TOOL_POLICY',
  'MOSAIC_AGENT_WORKDIR',
  'MOSAIC_TMUX_SOCKET',
] as const;

export const LOCAL_AGENT_ENV_KEYS = [
  'MOSAIC_RUNTIME_BIN',
  'MOSAIC_HEARTBEAT_RUN_DIR',
  'MOSAIC_HEARTBEAT_INTERVAL',
  'MOSAIC_CLAUDE_JSON',
  'CLAUDE_CONFIG_DIR',
] as const;

const GENERATED_KEY_SET = new Set<string>(GENERATED_AGENT_ENV_KEYS);
const LOCAL_KEY_SET = new Set<string>(LOCAL_AGENT_ENV_KEYS);
const SENSITIVE_KEY = /(?:API[_-]?KEY|AUTH|CREDENTIAL|PASSWORD|PRIVATE|SECRET|TOKEN)/i;
const AGENT_NAME = /^[A-Za-z0-9][A-Za-z0-9_.-]*$/;
const POLICY_NAME = /^[a-z][a-z0-9-]*$/;
const TMUX_SOCKET = /^[A-Za-z0-9_.-]*$/;
const MODEL = /^[A-Za-z0-9._/:+-]*$/;
/** Runtime launchers supported by the generated environment contract. */
export const GENERATED_AGENT_ENV_SUPPORTED_RUNTIMES = [
  'claude',
  'codex',
  'opencode',
  'pi',
] as const;

const SUPPORTED_RUNTIMES = new Set<string>(GENERATED_AGENT_ENV_SUPPORTED_RUNTIMES);
const REASONING = new Set(['', 'low', 'medium', 'high']);

/** Parses a strict data-only generated or local environment file without shell evaluation. */
export function parseAgentEnvironment(
  source: string,
  kind: AgentEnvironmentKind,
): Readonly<Record<string, string>> {
  const values: Record<string, string> = {};
  const seen = new Set<string>();

  for (const line of source.split('\n')) {
    if (line === '') continue;
    const match = /^([A-Z][A-Z0-9_]*)=(.*)$/.exec(line);
    if (!match) throw new AgentEnvBoundaryError('malformed-line', '(malformed)', line);

    const [, key, value] = match;
    if (key === undefined || value === undefined) {
      throw new AgentEnvBoundaryError('malformed-line', '(malformed)', line);
    }
    if (seen.has(key)) throw new AgentEnvBoundaryError('duplicate-key', key, value);
    seen.add(key);
    if (SENSITIVE_KEY.test(key)) throw new AgentEnvBoundaryError('sensitive-key', key, value);
    if (containsShellSyntax(value)) throw new AgentEnvBoundaryError('unsafe-value', key, value);

    if (kind === 'generated') {
      if (!GENERATED_KEY_SET.has(key)) throw new AgentEnvBoundaryError('unknown-key', key, value);
    } else {
      if (GENERATED_KEY_SET.has(key))
        throw new AgentEnvBoundaryError('generated-key-shadow', key, value);
      if (!LOCAL_KEY_SET.has(key)) throw new AgentEnvBoundaryError('unknown-key', key, value);
    }
    values[key] = value;
  }

  if (kind === 'generated') assertGeneratedValues(values);
  else assertLocalValues(values);
  return Object.freeze(values);
}

/** Renders the roster-derived generated projection in a stable, complete key order. */
export function renderGeneratedAgentEnvironment(values: Readonly<Record<string, string>>): string {
  const normalized = normalizeGeneratedValues(values);
  return `${GENERATED_AGENT_ENV_KEYS.map((key): string => `${key}=${normalized[key]}`).join('\n')}\n`;
}

/** Validates all deterministic projection inputs and target state without mutation. */
export async function prepareAgentEnvironmentProjection(
  options: AgentEnvironmentProjectionOptions,
): Promise<PreparedAgentEnvironmentProjection> {
  if (!AGENT_NAME.test(options.agentName)) {
    throw new AgentEnvBoundaryError('unsafe-agent-name', 'MOSAIC_AGENT_NAME', options.agentName);
  }

  await validatePrivateProjectionDirectory(options.mosaicHome, options.agentEnvDir);
  const generatedPath = join(options.agentEnvDir, `${options.agentName}.env.generated`);
  const localPath = join(options.agentEnvDir, `${options.agentName}.env.local`);
  const legacyPath = join(options.agentEnvDir, `${options.agentName}.env`);
  const generated = renderGeneratedAgentEnvironment(options.generated);
  await assertPrivateRegularFileIfPresent(generatedPath);
  const currentLocal = await readOptionalPrivateFile(localPath);
  const parsedLocal =
    currentLocal === undefined ? {} : parseAgentEnvironment(currentLocal, 'local');
  const legacy = await readOptionalPrivateFile(legacyPath);
  const legacyDisposition =
    legacy === undefined ? emptyLegacyDisposition() : classifyLegacyEnvironment(legacy);

  for (const [key, value] of Object.entries(legacyDisposition.localValues)) {
    if (parsedLocal[key] !== undefined && parsedLocal[key] !== value) {
      throw new AgentEnvBoundaryError('legacy-local-conflict', key, value);
    }
  }

  const local = renderLocalAgentEnvironment({ ...legacyDisposition.localValues, ...parsedLocal });
  const quarantinePath = legacyDisposition.diagnostics.length
    ? join(options.agentEnvDir, `${options.agentName}.env.quarantine`)
    : undefined;
  if (quarantinePath !== undefined) {
    const existingQuarantine = await readOptionalPrivateFile(quarantinePath);
    if (existingQuarantine !== undefined) {
      throw new AgentEnvBoundaryError('quarantine-exists', '(quarantine)', existingQuarantine);
    }
  }

  return {
    mosaicHome: options.mosaicHome,
    agentEnvDir: options.agentEnvDir,
    generatedPath,
    localPath,
    legacyPath,
    generated,
    local,
    ...(legacy === undefined ? {} : { legacy }),
    legacyRelocatedKeys: Object.keys(legacyDisposition.localValues).sort(compareCodePoints),
    ...(quarantinePath === undefined ? {} : { quarantinePath }),
    diagnostics: legacyDisposition.diagnostics,
  };
}

/**
 * Validates only the exact generated projection eligible for a roster delete.
 * Local overrides, legacy input, and quarantine records are operator-retained and
 * intentionally excluded from delete validation and cleanup.
 */
export async function prepareAgentGeneratedProjectionDeletion(
  options: AgentGeneratedProjectionDeletionOptions,
): Promise<string> {
  if (!AGENT_NAME.test(options.agentName)) {
    throw new AgentEnvBoundaryError('unsafe-agent-name', 'MOSAIC_AGENT_NAME', options.agentName);
  }
  await validatePrivateProjectionDirectory(options.mosaicHome, options.agentEnvDir);
  const generatedPath = join(options.agentEnvDir, `${options.agentName}.env.generated`);
  await assertPrivateRegularFileIfPresent(generatedPath);
  return generatedPath;
}

export async function previewAgentEnvironmentProjection(
  options: AgentEnvironmentProjectionOptions,
): Promise<AgentEnvironmentProjectionPreview> {
  const prepared = await prepareAgentEnvironmentProjection(options);
  const relocatedKeys = prepared.legacyRelocatedKeys;
  const legacy =
    prepared.legacy === undefined
      ? 'absent'
      : prepared.diagnostics.length > 0
        ? 'quarantine'
        : relocatedKeys.length > 0
          ? 'relocate-local'
          : 'regenerate-only';
  return {
    agentName: options.agentName,
    generated: 'rebuild',
    legacy,
    relocatedKeys,
    diagnostics: [...prepared.diagnostics].sort((left, right): number =>
      compareCodePoints(
        `${left.key}:${left.code}:${left.sha256}`,
        `${right.key}:${right.code}:${right.sha256}`,
      ),
    ),
  };
}

/** Applies a previously prepared deterministic projection. */
export async function applyPreparedAgentEnvironmentProjection(
  prepared: PreparedAgentEnvironmentProjection,
): Promise<AgentEnvironmentProjectionResult> {
  await ensurePrivateProjectionDirectory(prepared.mosaicHome, prepared.agentEnvDir);
  await writePrivateAtomically(prepared.generatedPath, prepared.generated);
  if (prepared.local !== '') await writePrivateAtomically(prepared.localPath, prepared.local);
  if (prepared.quarantinePath !== undefined && prepared.legacy !== undefined) {
    await writePrivateAtomically(prepared.quarantinePath, prepared.legacy);
  }
  if (prepared.legacy !== undefined) await unlink(prepared.legacyPath);

  return {
    generatedPath: prepared.generatedPath,
    localPath: prepared.localPath,
    ...(prepared.quarantinePath === undefined ? {} : { quarantinePath: prepared.quarantinePath }),
    diagnostics: prepared.diagnostics,
  };
}

/** Writes deterministic projection files and explicitly removes legacy `.env` authority. */
export async function writeAgentEnvironmentProjection(
  options: AgentEnvironmentProjectionOptions,
): Promise<AgentEnvironmentProjectionResult> {
  return applyPreparedAgentEnvironmentProjection(await prepareAgentEnvironmentProjection(options));
}

/** Creates the canonical managed roster path with private fresh-chain permissions. */
export async function writeManagedFleetRoster(
  mosaicHome: string,
  rosterPath: string,
  content: string,
): Promise<void> {
  const fleetDir = join(mosaicHome, 'fleet');
  const expectedRosterPath = join(fleetDir, 'roster.yaml');
  if (resolve(rosterPath) !== resolve(expectedRosterPath)) {
    throw new AgentEnvBoundaryError('unsafe-file', '(roster)', rosterPath);
  }
  await ensureManagedDirectory(mosaicHome, false);
  await ensureManagedDirectory(fleetDir, false);
  await writePrivateAtomically(rosterPath, content);
}

/** Ensures the private install-derived identity used to own a named tmux server. */
export async function ensureFleetHolderIdentity(mosaicHome: string): Promise<string> {
  const fleetDir = join(mosaicHome, 'fleet');
  const runDir = join(fleetDir, 'run');
  const identityPath = join(runDir, 'holder-owner');
  await ensureManagedDirectory(mosaicHome, false);
  await ensureManagedDirectory(fleetDir, false);
  await ensureManagedDirectory(runDir, true);
  const existing = await readOptionalPrivateFile(identityPath);
  if (existing !== undefined) {
    const identity = existing.trim();
    if (!/^[a-f0-9-]{36}$/.test(identity)) {
      throw new AgentEnvBoundaryError('unsafe-owner-identity', '(holder-owner)', existing);
    }
    return identity;
  }
  const identity = randomUUID();
  await writePrivateAtomically(identityPath, `${identity}\n`);
  return identity;
}

function normalizeGeneratedValues(
  values: Readonly<Record<string, string>>,
): Readonly<Record<string, string>> {
  const normalized: Record<string, string> = {};
  for (const key of GENERATED_AGENT_ENV_KEYS) {
    const value = values[key];
    if (value === undefined) throw new AgentEnvBoundaryError('missing-key', key, '');
    normalized[key] = key === 'MOSAIC_AGENT_WORKDIR' ? expandHomeDirectory(value) : value;
  }
  for (const [key, value] of Object.entries(values)) {
    if (!GENERATED_KEY_SET.has(key)) throw new AgentEnvBoundaryError('unknown-key', key, value);
  }
  assertGeneratedValues(normalized);
  return Object.freeze(normalized);
}

function expandHomeDirectory(path: string): string {
  if (path === '~') return homedir();
  if (!path.startsWith('~/') || path.split('/').includes('..')) return path;
  return join(homedir(), path.slice(2));
}

function renderLocalAgentEnvironment(values: Readonly<Record<string, string>>): string {
  if (Object.keys(values).length === 0) return '';
  const parsed = parseAgentEnvironment(
    Object.entries(values)
      .sort(([left], [right]): number => compareCodePoints(left, right))
      .map(([key, value]): string => `${key}=${value}`)
      .join('\n'),
    'local',
  );
  return `${Object.entries(parsed)
    .sort(([left], [right]): number => compareCodePoints(left, right))
    .map(([key, value]): string => `${key}=${value}`)
    .join('\n')}\n`;
}

function assertGeneratedValues(values: Readonly<Record<string, string>>): void {
  for (const key of GENERATED_AGENT_ENV_KEYS) {
    const value = values[key];
    if (value === undefined) throw new AgentEnvBoundaryError('missing-key', key, '');
  }
  const name = requiredGeneratedValue(values, 'MOSAIC_AGENT_NAME');
  const className = requiredGeneratedValue(values, 'MOSAIC_AGENT_CLASS');
  const runtime = requiredGeneratedValue(values, 'MOSAIC_AGENT_RUNTIME');
  const model = requiredGeneratedValue(values, 'MOSAIC_AGENT_MODEL');
  const reasoning = requiredGeneratedValue(values, 'MOSAIC_AGENT_REASONING');
  const toolPolicy = requiredGeneratedValue(values, 'MOSAIC_AGENT_TOOL_POLICY');
  const workingDirectory = requiredGeneratedValue(values, 'MOSAIC_AGENT_WORKDIR');
  const socket = requiredGeneratedValue(values, 'MOSAIC_TMUX_SOCKET');

  if (!AGENT_NAME.test(name))
    throw new AgentEnvBoundaryError('unsafe-agent-name', 'MOSAIC_AGENT_NAME', name);
  if (!POLICY_NAME.test(className)) {
    throw new AgentEnvBoundaryError('unsafe-class', 'MOSAIC_AGENT_CLASS', className);
  }
  if (!SUPPORTED_RUNTIMES.has(runtime)) {
    throw new AgentEnvBoundaryError('unsupported-runtime', 'MOSAIC_AGENT_RUNTIME', runtime);
  }
  if (!MODEL.test(model))
    throw new AgentEnvBoundaryError('unsafe-model', 'MOSAIC_AGENT_MODEL', model);
  if (!REASONING.has(reasoning)) {
    throw new AgentEnvBoundaryError('unsupported-reasoning', 'MOSAIC_AGENT_REASONING', reasoning);
  }
  if (toolPolicy !== '' && !POLICY_NAME.test(toolPolicy)) {
    throw new AgentEnvBoundaryError('unsafe-tool-policy', 'MOSAIC_AGENT_TOOL_POLICY', toolPolicy);
  }
  if (!isSafeAbsolutePath(workingDirectory)) {
    throw new AgentEnvBoundaryError('unsafe-path', 'MOSAIC_AGENT_WORKDIR', workingDirectory);
  }
  if (!TMUX_SOCKET.test(socket)) {
    throw new AgentEnvBoundaryError('unsafe-socket', 'MOSAIC_TMUX_SOCKET', socket);
  }
}

function requiredGeneratedValue(values: Readonly<Record<string, string>>, key: string): string {
  const value = values[key];
  if (value === undefined) throw new AgentEnvBoundaryError('missing-key', key, '');
  return value;
}

function assertLocalValues(values: Readonly<Record<string, string>>): void {
  for (const [key, value] of Object.entries(values)) {
    if (key === 'MOSAIC_HEARTBEAT_INTERVAL') {
      if (!/^[1-9][0-9]*$/.test(value)) {
        throw new AgentEnvBoundaryError('invalid-interval', key, value);
      }
      continue;
    }
    if (!isSafeAbsolutePath(value)) throw new AgentEnvBoundaryError('unsafe-path', key, value);
  }
}

function isSafeAbsolutePath(value: string): boolean {
  return (
    value.startsWith('/') && !value.split('/').includes('..') && !/[\s"'`$\\;&|<>(){}]/.test(value)
  );
}

function containsShellSyntax(value: string): boolean {
  return /["'`$\\;&|<>(){}]/.test(value);
}

interface LegacyDisposition {
  readonly localValues: Readonly<Record<string, string>>;
  readonly diagnostics: readonly AgentEnvironmentDiagnostic[];
}

function emptyLegacyDisposition(): LegacyDisposition {
  return { localValues: {}, diagnostics: [] };
}

function classifyLegacyEnvironment(source: string): LegacyDisposition {
  const localValues: Record<string, string> = {};
  const diagnostics: AgentEnvironmentDiagnostic[] = [];
  const seen = new Set<string>();

  for (const line of source.split('\n')) {
    if (line === '') continue;
    const match = /^([A-Z][A-Z0-9_]*)=(.*)$/.exec(line);
    if (!match || match[1] === undefined || match[2] === undefined) {
      diagnostics.push(diagnostic('malformed-line', '(malformed)', line));
      continue;
    }
    const [, key, value] = match;
    if (seen.has(key)) {
      diagnostics.push(diagnostic('duplicate-key', key, value));
      continue;
    }
    seen.add(key);
    if (GENERATED_KEY_SET.has(key)) continue;
    try {
      parseAgentEnvironment(`${key}=${value}\n`, 'local');
      localValues[key] = value;
    } catch (error: unknown) {
      if (error instanceof AgentEnvBoundaryError) diagnostics.push(error.diagnostic);
      else throw error;
    }
  }

  return { localValues: Object.freeze(localValues), diagnostics: Object.freeze(diagnostics) };
}

function diagnostic(code: string, key: string, value: string): AgentEnvironmentDiagnostic {
  return { code, key, sha256: hashValue(value) };
}

function hashValue(value: string): string {
  return createHash('sha256').update(value).digest('hex');
}

async function readOptionalPrivateFile(path: string): Promise<string | undefined> {
  try {
    await assertPrivateRegularFile(path);
    return await readFile(path, 'utf8');
  } catch (error: unknown) {
    if (isMissingFile(error)) return undefined;
    throw error;
  }
}

function isMissingFile(error: unknown): boolean {
  return typeof error === 'object' && error !== null && 'code' in error && error.code === 'ENOENT';
}

async function validatePrivateProjectionDirectory(
  mosaicHome: string,
  agentEnvDir: string,
): Promise<void> {
  const fleetDir = join(mosaicHome, 'fleet');
  const expectedAgentEnvDir = join(fleetDir, 'agents');
  if (resolve(agentEnvDir) !== resolve(expectedAgentEnvDir)) {
    throw new AgentEnvBoundaryError('unsafe-directory', '(directory)', agentEnvDir);
  }
  await assertManagedDirectoryIfPresent(mosaicHome, false);
  await assertManagedDirectoryIfPresent(fleetDir, false);
  await assertManagedDirectoryIfPresent(agentEnvDir, true);
}

async function ensurePrivateProjectionDirectory(
  mosaicHome: string,
  agentEnvDir: string,
): Promise<void> {
  await validatePrivateProjectionDirectory(mosaicHome, agentEnvDir);
  const fleetDir = join(mosaicHome, 'fleet');
  await ensureManagedDirectory(mosaicHome, false);
  await ensureManagedDirectory(fleetDir, false);
  await ensureManagedDirectory(agentEnvDir, true);
}

async function ensureManagedDirectory(path: string, privateDirectory: boolean): Promise<void> {
  let created = false;
  try {
    await lstat(path);
  } catch (error: unknown) {
    if (!isMissingFile(error)) throw error;
    try {
      await mkdir(path, { recursive: true, mode: 0o700 });
      created = true;
    } catch (mkdirError: unknown) {
      if (!isAlreadyExists(mkdirError)) throw mkdirError;
    }
  }

  await assertManagedDirectory(path, privateDirectory);
  if (created) {
    await chmod(path, 0o700);
    await assertManagedDirectory(path, privateDirectory);
  }
}

function isAlreadyExists(error: unknown): boolean {
  return typeof error === 'object' && error !== null && 'code' in error && error.code === 'EEXIST';
}

async function assertManagedDirectoryIfPresent(
  path: string,
  privateDirectory: boolean,
): Promise<void> {
  try {
    await assertManagedDirectory(path, privateDirectory);
  } catch (error: unknown) {
    if (isMissingFile(error)) return;
    throw error;
  }
}

async function assertManagedDirectory(path: string, privateDirectory: boolean): Promise<void> {
  const metadata = await lstat(path);
  if (!metadata.isDirectory()) {
    throw new AgentEnvBoundaryError('unsafe-directory', '(directory)', path);
  }
  if ((metadata.mode & 0o022) !== 0 || (privateDirectory && (metadata.mode & 0o077) !== 0)) {
    throw new AgentEnvBoundaryError('unsafe-permissions', '(directory)', path);
  }
}

async function assertPrivateRegularFileIfPresent(path: string): Promise<void> {
  try {
    await assertPrivateRegularFile(path);
  } catch (error: unknown) {
    if (isMissingFile(error)) return;
    throw error;
  }
}

async function assertPrivateRegularFile(path: string): Promise<void> {
  const metadata = await lstat(path);
  if (!metadata.isFile()) throw new AgentEnvBoundaryError('unsafe-file', '(file)', path);
  if ((metadata.mode & 0o077) !== 0) {
    throw new AgentEnvBoundaryError('unsafe-permissions', '(file)', path);
  }
}

async function writePrivateAtomically(path: string, content: string): Promise<void> {
  try {
    await assertPrivateRegularFile(path);
  } catch (error: unknown) {
    if (!isMissingFile(error)) throw error;
  }
  const temporaryPath = join(dirname(path), `.${randomUUID()}.tmp`);
  await writeFile(temporaryPath, content, { encoding: 'utf8', mode: 0o600, flag: 'wx' });
  await rename(temporaryPath, path);
}