import type {
  ActivityResult,
  AiDecision,
  ApiError,
  AuditEntry,
  DetailViewResponse,
  FormScreenResponse,
  LoginResponse,
  OcrResult,
  RecordViewParams,
  RecordViewResponse,
  Row,
  User,
} from './types';
import { APP_ID, WORKFLOW } from './config';

const TOKEN_KEY = 'hdfc_loan_desk_token';

/**
 * HTTP client for the Zino gateway.
 *
 * Most routes are app-scoped (`/app/524/...`); login and the AI-employee
 * monitor are not. The JWT persists in localStorage so a refresh does not
 * bounce the operator back to the login screen mid-disruption.
 */
export class ZinoClient {
  readonly baseUrl: string;
  private token: string | null = null;
  private onAuthError?: () => void;

  constructor(baseUrl: string, onAuthError?: () => void) {
    this.baseUrl = baseUrl.replace(/\/+$/, '');
    this.onAuthError = onAuthError;
    if (typeof window !== 'undefined') this.token = localStorage.getItem(TOKEN_KEY);
  }

  setAuthErrorHandler(fn: () => void): void {
    this.onAuthError = fn;
  }

  setToken(token: string | null): void {
    this.token = token;
    if (typeof window === 'undefined') return;
    if (token) localStorage.setItem(TOKEN_KEY, token);
    else localStorage.removeItem(TOKEN_KEY);
  }

  getToken(): string | null {
    return this.token;
  }

  private async request<T>(method: string, path: string, body?: unknown): Promise<T> {
    const headers: Record<string, string> = { 'Content-Type': 'application/json' };
    if (this.token) headers['Authorization'] = `Bearer ${this.token}`;

    const res = await fetch(`${this.baseUrl}${path}`, {
      method,
      headers,
      body: body !== undefined ? JSON.stringify(body) : undefined,
    });

    if (res.status === 401) {
      this.setToken(null);
      this.onAuthError?.();
      throw { status: 401, message: 'Session expired — sign in again' } as ApiError;
    }
    if (!res.ok) {
      let message = res.statusText;
      try {
        const j = (await res.json()) as { error?: string; message?: string };
        message = j.error || j.message || message;
      } catch {
        /* non-JSON body */
      }
      throw { status: res.status, message } as ApiError;
    }
    if (res.status === 204) return undefined as T;
    return (await res.json()) as T;
  }

  // --- Auth ---------------------------------------------------------------

  /** org_id must be a STRING. The gateway rejects a number with
   *  "cannot unmarshal number into Go struct field LoginRequest.org_id". */
  async login(email: string, password: string, orgId: string): Promise<LoginResponse> {
    const res = await this.request<LoginResponse>('POST', '/usr/login', {
      email,
      password,
      org_id: String(orgId),
    });
    this.setToken(res.token);
    return res;
  }

  logout(): void {
    this.setToken(null);
  }

  /** Decode the persisted JWT into a User — no network round trip, so a hard
   *  refresh restores the session without flashing the login screen. */
  currentUser(): User | null {
    if (!this.token) return null;
    try {
      const p = JSON.parse(atob(this.token.split('.')[1]));
      return {
        id: String(p.user_id ?? p.sub ?? ''),
        org_id: String(p.org_id ?? ''),
        name: p.name ?? '',
        email: p.email ?? '',
        roles: p.roles ?? [],
        groups: p.groups ?? [],
      };
    } catch {
      return null;
    }
  }

  // --- Views --------------------------------------------------------------

  async recordView(rvUid: string, params: RecordViewParams = {}): Promise<RecordViewResponse> {
    return this.request<RecordViewResponse>('POST', `/app/${APP_ID}/view/recordview`, {
      rv_template_uid: rvUid,
      search_query: {
        page: params.page ?? 1,
        limit: params.limit ?? 50,
        sort_by: params.sortBy ?? '',
        sort_dir: params.sortDir ?? 'desc',
        search: params.search ?? '',
        filters: (params.filters ?? []).map((f) => ({
          field_key: f.field_key,
          value: f.value,
          value2: '',
          data_type: f.data_type ?? 'string',
        })),
      },
    });
  }

  /** Rows only. The response key differs by source type — workflow views
   *  return `data`, rdbms views have been seen returning `records`. */
  async rows(rvUid: string, params: RecordViewParams = {}): Promise<Row[]> {
    const r = await this.recordView(rvUid, params);
    return r.data ?? r.records ?? [];
  }

  detailView(dvUid: string, instanceId: number | string): Promise<DetailViewResponse> {
    return this.request<DetailViewResponse>(
      'GET',
      `/app/${APP_ID}/view/detailview/${dvUid}?instance_id=${encodeURIComponent(String(instanceId))}`,
    );
  }

  async audit(instanceId: number | string): Promise<AuditEntry[]> {
    const rows = await this.request<AuditEntry[]>(
      'GET',
      `/app/${APP_ID}/view/audit?instance_id=${encodeURIComponent(String(instanceId))}`,
    );
    // One SUBMISSION writes several audit rows: a dispatch record, a
    // trigger-pipeline record, and finally the commit (whose
    // execution_state is the state id, and which carries the badge). The
    // history screen was rendering all of them, so every activity appeared
    // three times with identical text. Only the commit row is the event a
    // person means by "what happened"; the rest are the engine's own
    // bookkeeping, kept in the DB for reconciliation and deliberately not
    // shown. Filtered by prefix because the set of plumbing constants has
    // grown before (TRIGGER_DISPATCHED_POST_COMMIT is historical-only).
    return (rows ?? []).filter((r) => !String(r.execution_state ?? '').startsWith('TRIGGER_'));
  }

  /** AI-employee decisions for an instance. Public monitor route. */
  aiDecisions(instanceId: number | string): Promise<AiDecision[]> {
    return this.request<{ decisions: AiDecision[] }>(
      'GET',
      `/monitor/decisions?instance_id=${encodeURIComponent(String(instanceId))}`,
    ).then((r) => r.decisions ?? []);
  }

  // --- Forms --------------------------------------------------------------

  /** The live definition of an activity's form: fields, types, select options
   *  and which are mandatory. Read at open time rather than hardcoded, so a
   *  field added in Studio appears here without a frontend change. */
  formSchema(activityUid: string, instanceId?: number | string): Promise<FormScreenResponse> {
    return this.request<FormScreenResponse>('POST', `/app/${APP_ID}/view/form-screens`, {
      activity_id: activityUid,
      device_type: 'desktop',
      ...(instanceId != null ? { instance_id: numericId(instanceId) } : {}),
    });
  }

  // --- Document intelligence ----------------------------------------------

  /**
   * Run OCR on an uploaded document for an `ocr` field.
   *
   * The extraction contract is NOT sent from here. The endpoint resolves the
   * field's `ocr_config` server-side from the deployed workflow config and
   * ignores anything a client supplies — so which values come back is decided
   * by the field's configuration, and the response keys are exactly that
   * config's `extraction_fields[].key`.
   *
   * `instanceId` is omitted on an INIT activity, where no instance exists yet.
   *
   * This deliberately bypasses `request()`: it must NOT set Content-Type. The
   * browser has to write `multipart/form-data; boundary=…` itself, and setting
   * that header by hand omits the boundary, after which the server rejects the
   * body as malformed multipart.
   */
  async ocrExtract(
    activityUid: string,
    fieldId: string,
    file: File,
    instanceId?: number | string,
  ): Promise<OcrResult> {
    const fd = new FormData();
    fd.append('file', file);
    fd.append('workflow_uuid', WORKFLOW);
    fd.append('activity_id', activityUid);
    fd.append('field_id', fieldId);
    if (instanceId != null && instanceId !== '') {
      fd.append('instance_id', String(numericId(instanceId)));
    }

    const headers: Record<string, string> = {};
    if (this.token) headers['Authorization'] = `Bearer ${this.token}`;

    const res = await fetch(`${this.baseUrl}/app/${APP_ID}/ocr-extract`, {
      method: 'POST',
      headers,
      body: fd,
    });

    if (res.status === 401) {
      this.setToken(null);
      this.onAuthError?.();
      throw { status: 401, message: 'Session expired — sign in again' } as ApiError;
    }
    if (!res.ok) {
      let message = res.statusText;
      try {
        const j = (await res.json()) as { error?: string; message?: string };
        message = j.error || j.message || message;
      } catch {
        /* non-JSON body */
      }
      throw { status: res.status, message } as ApiError;
    }
    return (await res.json()) as OcrResult;
  }

  // --- Workflow execution -------------------------------------------------

  /** Start a new instance (an INIT activity such as Register Flight). */
  startInstance(
    workflowUuid: string,
    activityUid: string,
    data: Record<string, unknown>,
  ): Promise<ActivityResult> {
    return this.request<ActivityResult>('POST', `/app/${APP_ID}/start`, {
      workflow_uuid: workflowUuid,
      activity_id: activityUid,
      data,
    });
  }

  /** Perform an activity on an existing instance. The workflow refuses
   *  anything the current state does not allow — that refusal is a feature,
   *  not an error to paper over. */
  performActivity(
    workflowUuid: string,
    instanceId: number | string,
    activityUid: string,
    data: Record<string, unknown>,
  ): Promise<ActivityResult> {
    return this.request<ActivityResult>('POST', `/app/${APP_ID}/activity`, {
      workflow_uuid: workflowUuid,
      instance_id: numericId(instanceId),
      activity_id: activityUid,
      data,
    });
  }
}

/**
 * Instance ids must go over the wire as JSON NUMBERS.
 *
 * The route params they come from are strings, and view-service decodes
 * `instance_id` into an int64 — so a quoted "9765" fails the decode and the
 * whole request comes back "Invalid request body" with no clue which field
 * was at fault. That is what broke Retry call: the form schema never loaded,
 * because the id had been carried straight through from useParams.
 *
 * performActivity had its own inline coercion and formSchema did not, which
 * is exactly the kind of divergence that survives review. One helper, used by
 * both.
 *
 * A non-numeric id is passed through untouched rather than becoming NaN — if
 * an id ever stops being an integer, the server should say so plainly instead
 * of receiving null.
 */
function numericId(id: number | string): number | string {
  if (typeof id === 'number') return id;
  const n = Number(id);
  return Number.isFinite(n) && id.trim() !== '' ? n : id;
}