/**
 * Settings Store integration for hot-reloading Tlon plugin config.
 * 
 * Settings are stored in Urbit's %settings agent under:
 *   desk: "moltbot"
 *   bucket: "tlon"
 * 
 * This allows config changes via poke from any Landscape client
 * without requiring a gateway restart.
 */

import type { UrbitSSEClient } from "./urbit/sse-client.js";

export type TlonSettingsStore = {
  groupChannels?: string[];
  dmAllowlist?: string[];
  autoDiscover?: boolean;
  showModelSig?: boolean;
  channelRules?: Record<string, {
    mode?: "restricted" | "open";
    allowedShips?: string[];
  }>;
  defaultAuthorizedShips?: string[];
};

export type TlonSettingsState = {
  current: TlonSettingsStore;
  loaded: boolean;
};

const SETTINGS_DESK = "moltbot";
const SETTINGS_BUCKET = "tlon";

/**
 * Parse channelRules - handles both JSON string and object formats.
 * Settings-store doesn't support nested objects, so we store as JSON string.
 */
function parseChannelRules(
  value: unknown
): Record<string, { mode?: "restricted" | "open"; allowedShips?: string[] }> | undefined {
  if (!value) return undefined;
  
  // If it's a string, try to parse as JSON
  if (typeof value === "string") {
    try {
      const parsed = JSON.parse(value);
      if (isChannelRulesObject(parsed)) return parsed;
    } catch {
      return undefined;
    }
  }
  
  // If it's already an object, use directly
  if (isChannelRulesObject(value)) return value;
  
  return undefined;
}

/**
 * Parse settings from the raw Urbit settings-store response.
 * The response shape is: { [bucket]: { [key]: value } }
 */
function parseSettingsResponse(raw: unknown): TlonSettingsStore {
  if (!raw || typeof raw !== "object") return {};
  
  const desk = raw as Record<string, unknown>;
  const bucket = desk[SETTINGS_BUCKET];
  if (!bucket || typeof bucket !== "object") return {};
  
  const settings = bucket as Record<string, unknown>;
  
  return {
    groupChannels: Array.isArray(settings.groupChannels) 
      ? settings.groupChannels.filter((x): x is string => typeof x === "string")
      : undefined,
    dmAllowlist: Array.isArray(settings.dmAllowlist)
      ? settings.dmAllowlist.filter((x): x is string => typeof x === "string")
      : undefined,
    autoDiscover: typeof settings.autoDiscover === "boolean" 
      ? settings.autoDiscover 
      : undefined,
    showModelSig: typeof settings.showModelSig === "boolean"
      ? settings.showModelSig
      : undefined,
    channelRules: parseChannelRules(settings.channelRules),
    defaultAuthorizedShips: Array.isArray(settings.defaultAuthorizedShips)
      ? settings.defaultAuthorizedShips.filter((x): x is string => typeof x === "string")
      : undefined,
  };
}

function isChannelRulesObject(
  val: unknown
): val is Record<string, { mode?: "restricted" | "open"; allowedShips?: string[] }> {
  if (!val || typeof val !== "object" || Array.isArray(val)) return false;
  for (const [, rule] of Object.entries(val)) {
    if (!rule || typeof rule !== "object") return false;
  }
  return true;
}

/**
 * Parse a single settings entry update event.
 */
function parseSettingsEvent(event: unknown): { key: string; value: unknown } | null {
  if (!event || typeof event !== "object") return null;
  
  const evt = event as Record<string, unknown>;
  
  // Handle put-entry events
  if (evt["put-entry"]) {
    const put = evt["put-entry"] as Record<string, unknown>;
    if (put.desk !== SETTINGS_DESK || put["bucket-key"] !== SETTINGS_BUCKET) {
      return null;
    }
    return {
      key: String(put["entry-key"] ?? ""),
      value: put.value,
    };
  }
  
  // Handle del-entry events
  if (evt["del-entry"]) {
    const del = evt["del-entry"] as Record<string, unknown>;
    if (del.desk !== SETTINGS_DESK || del["bucket-key"] !== SETTINGS_BUCKET) {
      return null;
    }
    return {
      key: String(del["entry-key"] ?? ""),
      value: undefined,
    };
  }
  
  return null;
}

/**
 * Apply a single settings update to the current state.
 */
function applySettingsUpdate(
  current: TlonSettingsStore,
  key: string,
  value: unknown
): TlonSettingsStore {
  const next = { ...current };
  
  switch (key) {
    case "groupChannels":
      next.groupChannels = Array.isArray(value)
        ? value.filter((x): x is string => typeof x === "string")
        : undefined;
      break;
    case "dmAllowlist":
      next.dmAllowlist = Array.isArray(value)
        ? value.filter((x): x is string => typeof x === "string")
        : undefined;
      break;
    case "autoDiscover":
      next.autoDiscover = typeof value === "boolean" ? value : undefined;
      break;
    case "showModelSig":
      next.showModelSig = typeof value === "boolean" ? value : undefined;
      break;
    case "channelRules":
      next.channelRules = parseChannelRules(value);
      break;
    case "defaultAuthorizedShips":
      next.defaultAuthorizedShips = Array.isArray(value)
        ? value.filter((x): x is string => typeof x === "string")
        : undefined;
      break;
  }
  
  return next;
}

export type SettingsLogger = {
  log?: (msg: string) => void;
  error?: (msg: string) => void;
};

/**
 * Create a settings store subscription manager.
 * 
 * Usage:
 *   const settings = createSettingsManager(api, logger);
 *   await settings.load();
 *   settings.subscribe((newSettings) => { ... });
 */
export function createSettingsManager(
  api: UrbitSSEClient,
  logger?: SettingsLogger
) {
  let state: TlonSettingsState = {
    current: {},
    loaded: false,
  };
  
  const listeners = new Set<(settings: TlonSettingsStore) => void>();
  
  const notify = () => {
    for (const listener of listeners) {
      try {
        listener(state.current);
      } catch (err) {
        logger?.error?.(`[settings] Listener error: ${String(err)}`);
      }
    }
  };
  
  return {
    /**
     * Get current settings (may be empty if not loaded yet).
     */
    get current(): TlonSettingsStore {
      return state.current;
    },
    
    /**
     * Whether initial settings have been loaded.
     */
    get loaded(): boolean {
      return state.loaded;
    },
    
    /**
     * Load initial settings via scry.
     */
    async load(): Promise<TlonSettingsStore> {
      try {
        const raw = await api.scry(`/desk/${SETTINGS_DESK}.json`);
        state.current = parseSettingsResponse(raw);
        state.loaded = true;
        logger?.log?.(`[settings] Loaded: ${JSON.stringify(state.current)}`);
        return state.current;
      } catch (err) {
        // Settings desk may not exist yet - that's fine, use defaults
        logger?.log?.(`[settings] No settings found (using defaults): ${String(err)}`);
        state.current = {};
        state.loaded = true;
        return state.current;
      }
    },
    
    /**
     * Subscribe to settings changes.
     */
    async startSubscription(): Promise<void> {
      await api.subscribe({
        app: "settings",
        path: "/desk/" + SETTINGS_DESK,
        event: (event) => {
          const update = parseSettingsEvent(event);
          if (!update) return;
          
          logger?.log?.(`[settings] Update: ${update.key} = ${JSON.stringify(update.value)}`);
          state.current = applySettingsUpdate(state.current, update.key, update.value);
          notify();
        },
        err: (error) => {
          logger?.error?.(`[settings] Subscription error: ${String(error)}`);
        },
        quit: () => {
          logger?.log?.("[settings] Subscription ended");
        },
      });
      logger?.log?.("[settings] Subscribed to settings updates");
    },
    
    /**
     * Register a listener for settings changes.
     */
    onChange(listener: (settings: TlonSettingsStore) => void): () => void {
      listeners.add(listener);
      return () => listeners.delete(listener);
    },
  };
}