import {
  parseClientConfiguration,
  serializeClientConfiguration,
  clientServerPath,
  legacyClientServerPath,
  withClientServers,
  type ClientConfigurationDocument,
} from "./ClientConfigurationDocument.js";
import { copyFile, lstat, readFile, realpath, rm } from "node:fs/promises";
import { homedir } from "node:os";
import { join } from "node:path";

import writeFileAtomic from "write-file-atomic";
import { z } from "zod";

import { PRODUCT_IDENTITY } from "../identity.js";
import { isOwnedClientRegistrationCommand } from "./ClientRegistrationIdentity.js";
import { resolveClientConfigTransactionPath } from "./ClientConfigPath.js";
import {
  manualRegistrationRemediation,
  supportedClients,
  type SetupClient,
} from "./SupportedClients.js";

interface ManagedPathStats {
  readonly uid?: number;
  isFile?(): boolean;
  isSymbolicLink(): boolean;
}

/** Injectable filesystem operations used to prove uninstall failure recovery. */
export interface UninstallFileSystem {
  readText(path: string): Promise<string>;
  copy(source: string, destination: string): Promise<void>;
  writeText(path: string, contents: string): Promise<void>;
  stat(path: string): Promise<ManagedPathStats>;
  realpath?(path: string): Promise<string>;
  remove(path: string): Promise<void>;
}

const systemFileSystem: UninstallFileSystem = {
  readText: (path) => readFile(path, "utf8"),
  copy: (source, destination) => copyFile(source, destination),
  writeText: (path, contents) =>
    writeFileAtomic(path, contents, { encoding: "utf8" }),
  stat: (path) => lstat(path),
  realpath: (path) => realpath(path),
  remove: (path) => rm(path, { recursive: true }),
};

/** One explicitly classified uninstall action. */
export interface UninstallItem {
  readonly name: string;
  readonly status: "removed" | "retained" | "skipped" | "failed";
  readonly detail: string;
}

/** Structured, idempotent result of removing REA-owned state. */
export interface UninstallResult {
  readonly status: "complete" | "failed";
  readonly items: readonly UninstallItem[];
}

/** Whether any requested REA-owned uninstall action failed. */
export const isUninstallFailure = (result: UninstallResult): boolean => {
  const status = result.status;
  switch (status) {
    case "complete":
      return false;
    case "failed":
      return true;
    default: {
      const exhaustive: never = status;
      throw new TypeError(
        `Unhandled uninstall result status: ${String(exhaustive)}`,
      );
    }
  }
};

/** Filesystem boundary used by the contained uninstall workflow. */
export interface UninstallHost {
  clients(): Promise<readonly SetupClient[]>;
  /** Report a configuration that cannot be read safely, before any removal. */
  inspectClient(client: SetupClient): Promise<UninstallItem | undefined>;
  removeClient(client: SetupClient): Promise<UninstallItem>;
  removeSkill(): Promise<UninstallItem>;
  purgeData(): Promise<readonly UninstallItem[]>;
}

/**
 * Remove only REA-owned registrations and managed files, optionally including
 * local state. A client configuration that cannot be read safely stops the
 * operation before anything is removed; one that fails during removal stops
 * the remaining removals.
 */
export const runUninstall = async (
  purgeData: boolean,
  host: UninstallHost = systemUninstallHost(),
): Promise<UninstallResult> => {
  const clients = await host.clients();
  const blocked: UninstallItem[] = [];
  for (const client of clients) {
    const blocking = await host.inspectClient(client);
    if (blocking !== undefined) blocked.push(blocking);
  }
  const items: UninstallItem[] =
    blocked.length > 0
      ? [
          ...blocked,
          item(
            "uninstall",
            "skipped",
            "No REA registration, skill, or data was removed. Repair each failed configuration, then rerun uninstall.",
          ),
        ]
      : await removeAll(clients, purgeData, host);
  items.push({
    name: "analysis_engine",
    status: "retained",
    detail: "Hopper is not owned by REA uninstall.",
  });
  return {
    status: items.some(({ status }) => status === "failed")
      ? "failed"
      : "complete",
    items,
  };
};

/**
 * Each client is reread when it is edited, so a concurrent change is never
 * overwritten. A client that fails then still stops the remaining removals.
 */
const removeAll = async (
  clients: readonly SetupClient[],
  purgeData: boolean,
  host: UninstallHost,
): Promise<UninstallItem[]> => {
  const items: UninstallItem[] = [];
  for (const client of clients) {
    const removed = await host.removeClient(client);
    items.push(removed);
    if (removed.status === "failed")
      return [
        ...items,
        item(
          "uninstall",
          "skipped",
          "Uninstall stopped at this failure; the items above report what changed. Repair the failed configuration, then rerun uninstall.",
        ),
      ];
  }
  items.push(await host.removeSkill());
  if (purgeData) items.push(...(await host.purgeData()));
  return items;
};

/** Create uninstall effects contained to detected client configs and REA-owned paths. */
export const systemUninstallHost = (
  home = homedir(),
  fileSystem: UninstallFileSystem = systemFileSystem,
): UninstallHost => ({
  clients: () => Promise.resolve(supportedClients(home)),
  inspectClient: async (client) => {
    const read = await readClientConfiguration(client, fileSystem);
    return read.kind === "item" && read.item.status === "failed"
      ? read.item
      : undefined;
  },
  removeClient: (client) => removeClient(client, fileSystem),
  removeSkill: () => removeManagedSkills(home, fileSystem),
  purgeData: async () => [
    await removeManagedPath(join(home, ".rea/cache"), "cache", fileSystem),
    await removeManagedPath(join(home, ".rea/state"), "state", fileSystem),
  ],
});

type ClientConfigurationRead =
  | { readonly kind: "item"; readonly item: UninstallItem }
  | {
      readonly kind: "configuration";
      readonly transactionPath: string;
      readonly original: string;
      readonly parsed: ClientConfigurationDocument;
    };

const readClientConfiguration = async (
  client: SetupClient,
  fileSystem: UninstallFileSystem,
): Promise<ClientConfigurationRead> => {
  if (client.format === "unsupported")
    return itemRead(
      item(
        client.name,
        "skipped",
        manualRegistrationRemediation(client.name) ??
          "This client has no documented local MCP configuration boundary.",
      ),
    );
  const resolved = await resolveUninstallConfigPath(client, fileSystem);
  if (typeof resolved !== "string") return itemRead(resolved);
  const transactionPath = resolved;
  let original: string;
  try {
    original = await fileSystem.readText(transactionPath);
  } catch (cause: unknown) {
    return itemRead(
      isMissing(cause)
        ? item(client.name, "skipped", "Configuration does not exist.")
        : item(
            client.name,
            "failed",
            "Configuration could not be read. Check file permissions, then rerun uninstall.",
          ),
    );
  }
  try {
    const parsed = parseClientConfiguration(original, client.format);
    return { kind: "configuration", transactionPath, original, parsed };
  } catch (cause: unknown) {
    void cause;
    return itemRead(
      item(
        client.name,
        "failed",
        `Configuration is not valid ${client.format === "toml" || client.format === "grok" ? "TOML" : client.format === "opencode" ? "JSONC" : "JSON"} and was not changed. Repair it, then rerun uninstall.`,
      ),
    );
  }
};

const itemRead = (result: UninstallItem): ClientConfigurationRead => ({
  kind: "item",
  item: result,
});

const removeClient = async (
  client: SetupClient,
  fileSystem: UninstallFileSystem,
): Promise<UninstallItem> => {
  const read = await readClientConfiguration(client, fileSystem);
  if (read.kind === "item") return read.item;
  const { transactionPath, original, parsed } = read;
  const name = PRODUCT_IDENTITY.mcpServerKey;
  // Beside a native OpenCode V2 table, OpenCode also loads a V1 `mcp.rea`.
  const legacyPath = legacyClientServerPath(parsed, name);
  const hasNative = Object.hasOwn(parsed.servers, name);
  if (!hasNative && legacyPath === undefined)
    return item(client.name, "skipped", "REA registration is absent.");
  const removeNative =
    hasNative && isOwnedRegistration(parsed.servers[name], client);
  const removeLegacy =
    legacyPath !== undefined &&
    isOwnedRegistration(parsed.legacyServers[name], client);
  if (!removeNative && !removeLegacy)
    return item(
      client.name,
      "retained",
      "The rea-named registration is not REA-owned.",
    );
  const remaining = { ...parsed.servers };
  if (removeNative) delete remaining[name];
  const document = withClientServers(
    parsed,
    remaining,
    removeLegacy ? name : undefined,
  );
  const editedPaths = [
    ...(removeNative ? [clientServerPath(parsed, name)] : []),
    ...(removeLegacy ? [legacyPath] : []),
  ];
  const backupPath = `${client.configPath}.rea.backup`;
  try {
    await fileSystem.copy(transactionPath, backupPath);
  } catch (cause: unknown) {
    void cause;
    return item(
      client.name,
      "failed",
      "Configuration could not be backed up, so no change was made. Check file permissions, then rerun uninstall.",
    );
  }
  try {
    await fileSystem.writeText(
      transactionPath,
      serializeClientConfiguration(
        document,
        client.format,
        original,
        editedPaths,
      ),
    );
    const readback = parseClientConfiguration(
      await fileSystem.readText(transactionPath),
      client.format,
    );
    if (
      (removeNative && Object.hasOwn(readback.servers, name)) ||
      (removeLegacy && Object.hasOwn(readback.legacyServers, name))
    )
      throw new Error("registration readback mismatch");
    return item(
      client.name,
      "removed",
      `Removed registration from ${client.configPath}.`,
    );
  } catch (cause: unknown) {
    // Update failure attempts a restore before reporting; cause is preserved below.
    void cause;
    try {
      await fileSystem.writeText(transactionPath, original);
    } catch (restoreCause: unknown) {
      void restoreCause;
      return item(
        client.name,
        "failed",
        "Configuration could not be updated or restored. Restore its `.rea.backup` manually, then rerun uninstall.",
      );
    }
    return item(
      client.name,
      "failed",
      "Configuration could not be updated. The original was restored and its `.rea.backup` was retained. Repair the configuration or restore the backup, then rerun uninstall.",
    );
  }
};

const resolveUninstallConfigPath = async (
  client: SetupClient,
  fileSystem: UninstallFileSystem,
): Promise<string | UninstallItem> => {
  const path = await resolveClientConfigTransactionPath(
    client.configPath,
    fileSystem.realpath === undefined
      ? { lstat: fileSystem.stat }
      : { lstat: fileSystem.stat, realpath: fileSystem.realpath },
  );
  return (
    path ??
    item(
      client.name,
      "failed",
      "Configuration path could not be safely verified. Check its permissions and, if it is a symbolic link, verify that the link resolves to a regular file owned by the current user, then rerun uninstall.",
    )
  );
};

/** Ownership rule for persistent MCP registrations created by REA setup. */
const isOwnedRegistration = (value: unknown, client: SetupClient): boolean => {
  if (client.format === "opencode") {
    const parsed = z
      .object({ type: z.literal("local"), command: z.array(z.string()).min(1) })
      .passthrough()
      .safeParse(value);
    if (!parsed.success) return false;
    const command = parsed.data.command;
    return isOwnedClientRegistrationCommand(command);
  }
  const parsed = registrationSchema.safeParse(value);
  if (!parsed.success) return false;
  const { command, args } = parsed.data;
  return isOwnedClientRegistrationCommand([command, ...args]);
};

const removeManagedPath = async (
  path: string,
  name: string,
  fileSystem: UninstallFileSystem,
): Promise<UninstallItem> => {
  try {
    const stats = await fileSystem.stat(path);
    if (stats.isSymbolicLink())
      return item(
        name,
        "retained",
        "REA did not remove this item because its managed path is a symbolic link. Verify the link target before removing it manually.",
      );
    await fileSystem.remove(path);
    return item(name, "removed", `Removed ${path}.`);
  } catch (cause: unknown) {
    return isMissing(cause)
      ? item(name, "skipped", `${path} does not exist.`)
      : item(
          name,
          "failed",
          "This item could not be removed. Check file permissions, then rerun uninstall.",
        );
  }
};

const removeManagedSkills = async (
  home: string,
  fileSystem: UninstallFileSystem,
): Promise<UninstallItem> =>
  removeManagedPath(
    join(home, ".agents/skills", PRODUCT_IDENTITY.skillName),
    "skill",
    fileSystem,
  );

const item = (
  name: string,
  status: UninstallItem["status"],
  detail: string,
): UninstallItem => ({ name, status, detail });
const registrationSchema = z
  .object({ command: z.string(), args: z.array(z.string()) })
  .passthrough();
const isMissing = (cause: unknown): boolean =>
  cause instanceof Error && "code" in cause && cause.code === "ENOENT";