/**
 * API Error Handler Utility
 * Parses server error responses and extracts field-level validation errors.
 * Server text is mapped to safe, user-facing copy — raw messages are not echoed.
 */

import axios, { AxiosError } from "axios";
import { FieldValues, Path, UseFormSetError } from "react-hook-form";

/**
 * Standard API error response structure (and common variants we normalize).
 */
export interface ApiErrorResponse {
  message?: string;
  errors?: Record<string, string | string[] | unknown> | unknown;
  error?: string | ApiNestedError | Record<string, unknown>;
  detail?: string | string[] | Record<string, string[] | unknown> | FastApiDetailItem[];
}

interface ApiNestedError {
  message?: string;
  code?: string;
  errors?: Record<string, unknown>;
  details?: Record<string, unknown>;
}

interface FastApiDetailItem {
  loc?: unknown[];
  msg?: string;
  type?: string;
}

/**
 * Parsed error result
 */
export interface ParsedApiError {
  generalMessage: string;
  fieldErrors: Record<string, string>;
}

const DEFAULT_GENERAL = "Something went wrong. Please try again.";

/** Shown under a field when the server flagged it but we do not expose its raw text. */
const GENERIC_FIELD_MESSAGE =
  "This value could not be accepted. Check for typos and remove any HTML, scripts, or unusual symbols.";

const FIELD_NAME_MAP: Record<string, string> = {
  fullName: "full_name",
  full_name: "full_name",
  email: "email",
  phone: "phone",
  phoneNumber: "phone_number",
  phone_number: "phone_number",
  message: "message",
  companyName: "company_name",
  company_name: "company_name",
  workEmail: "work_email",
  work_email: "work_email",
};

const ERROR_MESSAGES: Record<string, string> = {
  invalid_input:
    "That does not look like valid input. Use plain text only — no HTML or scripts.",
  xss_detected:
    "Invalid content was detected. Remove any HTML tags, scripts, or code-like text.",
  validation_failed: "Please check this field and try again.",
  required: "This field is required.",
  invalid_email: "Please enter a valid email address.",
  invalid_phone: "Please enter a valid phone number using digits and common phone symbols only.",
  too_short: "This value is too short.",
  too_long: "This value is too long.",
  duplicate: "This value is already in use. Try a different one.",
  duplicate_inquiry:
    "You already have a pending inquiry with this email. Please wait for it to be processed.",
};

/**
 * Maps a single server token or short code to a friendly message.
 */
function mapErrorCode(code: string): string | null {
  const key = code.trim().toLowerCase().replace(/[\s-]+/g, "_");
  if (ERROR_MESSAGES[key]) return ERROR_MESSAGES[key];
  const aliases: Record<string, keyof typeof ERROR_MESSAGES> = {
    invalid_email_format: "invalid_email",
    email_invalid: "invalid_email",
    invalid_email: "invalid_email",
    invalid_phone_format: "invalid_phone",
    invalid_phone: "invalid_phone",
    phone_invalid: "invalid_phone",
    xss: "xss_detected",
    xss_detected: "xss_detected",
    malicious_content: "xss_detected",
    validation_error: "validation_failed",
    validation_failed: "validation_failed",
    duplicate_inquiry: "duplicate_inquiry",
    duplicate: "duplicate",
  };
  const mappedKey = aliases[key];
  return mappedKey ? ERROR_MESSAGES[mappedKey] : null;
}

/**
 * Infers a safe message from server hint text without echoing the full string.
 */
function inferMessageFromHint(hint: string): string {
  const h = hint.toLowerCase();
  if (/(xss|script|html|tag|malicious|injection)/i.test(hint)) {
    return ERROR_MESSAGES.xss_detected;
  }
  if (/email/.test(h)) return ERROR_MESSAGES.invalid_email;
  if (/phone|tel|mobile/.test(h)) return ERROR_MESSAGES.invalid_phone;
  if (/company|organization|organisation/.test(h)) {
    return "Please use a valid company name (plain text, no HTML or scripts).";
  }
  if (/name|full/.test(h)) {
    return "Please enter a valid name using letters and common characters only.";
  }
  if (/required|missing|empty/.test(h)) return ERROR_MESSAGES.required;
  if (/long|length|exceed/.test(h)) return ERROR_MESSAGES.too_long;
  if (/short|minimum/.test(h)) return ERROR_MESSAGES.too_short;
  if (/duplicate|already|exist/.test(h)) return ERROR_MESSAGES.duplicate_inquiry;
  return GENERIC_FIELD_MESSAGE;
}

function normalizeFieldName(fieldName: string): string {
  return FIELD_NAME_MAP[fieldName] || fieldName;
}

function isPlainObject(v: unknown): v is Record<string, unknown> {
  return typeof v === "object" && v !== null && !Array.isArray(v);
}

/**
 * Turns assorted server error values into a single user-safe string.
 */
function normalizeFieldErrorValue(value: unknown): string {
  if (value === null || value === undefined) return GENERIC_FIELD_MESSAGE;
  if (typeof value === "number" || typeof value === "boolean") {
    return mapErrorCode(String(value)) ?? GENERIC_FIELD_MESSAGE;
  }
  if (typeof value === "string") {
    const trimmed = value.trim();
    if (!trimmed) return GENERIC_FIELD_MESSAGE;
    const byCode = mapErrorCode(trimmed);
    if (byCode) return byCode;
    if (/^[a-z0-9_.]+$/i.test(trimmed) && trimmed.length <= 80) {
      return mapErrorCode(trimmed.replace(/\./g, "_")) ?? GENERIC_FIELD_MESSAGE;
    }
    return inferMessageFromHint(trimmed);
  }
  if (Array.isArray(value)) {
    const parts = value
      .map((v) => normalizeFieldErrorValue(v))
      .filter((s, i, arr) => s && arr.indexOf(s) === i);
    return parts.length ? parts.join(" ") : GENERIC_FIELD_MESSAGE;
  }
  if (isPlainObject(value)) {
    const msg =
      typeof value.message === "string"
        ? value.message
        : typeof value.msg === "string"
          ? value.msg
          : typeof value.detail === "string"
            ? value.detail
            : "";
    if (msg) return inferMessageFromHint(msg);
  }
  return GENERIC_FIELD_MESSAGE;
}

function mergeFieldErrors(
  target: Record<string, string>,
  source: Record<string, string>
): void {
  for (const [k, v] of Object.entries(source)) {
    const key = normalizeFieldName(k);
    target[key] = v;
  }
}

function parseErrorsRecord(record: Record<string, unknown>): Record<string, string> {
  const out: Record<string, string> = {};
  for (const [field, err] of Object.entries(record)) {
    out[field] = normalizeFieldErrorValue(err);
  }
  return out;
}

function parseFastApiDetailArray(items: FastApiDetailItem[]): Record<string, string> {
  const out: Record<string, string> = {};
  for (const item of items) {
    if (!item || typeof item !== "object") continue;
    const loc = Array.isArray(item.loc) ? item.loc : [];
    const rawKey = loc.filter((x): x is string => typeof x === "string").pop();
    const field = rawKey ? normalizeFieldName(rawKey) : "_form";
    const hint = item.msg ?? item.type ?? "";
    out[field] = hint ? inferMessageFromHint(String(hint)) : GENERIC_FIELD_MESSAGE;
  }
  return out;
}

function parseDetail(detail: unknown): Record<string, string> {
  if (!detail) return {};
  if (typeof detail === "string") {
    return { _form: inferMessageFromHint(detail) };
  }
  if (Array.isArray(detail)) {
    if (detail.length && typeof detail[0] === "object" && detail[0] !== null && "loc" in detail[0]) {
      return parseFastApiDetailArray(detail as FastApiDetailItem[]);
    }
    return { _form: normalizeFieldErrorValue(detail) };
  }
  if (isPlainObject(detail)) {
    return parseErrorsRecord(detail as Record<string, unknown>);
  }
  return {};
}

/**
 * Walks common API shapes and collects field errors + optional form-level key.
 */
function extractFieldErrorsFromBody(data: unknown): {
  fieldErrors: Record<string, string>;
  formLevel?: string;
} {
  const fieldErrors: Record<string, string> = {};
  let formLevel: string | undefined;

  if (!data) return { fieldErrors };

  if (typeof data === "string") {
    formLevel = inferMessageFromHint(data);
    return { fieldErrors, formLevel };
  }

  if (!isPlainObject(data)) return { fieldErrors };

  const d = data as Record<string, unknown>;

  if (isPlainObject(d.errors)) {
    mergeFieldErrors(fieldErrors, parseErrorsRecord(d.errors as Record<string, unknown>));
  }

  if (Array.isArray(d.errors)) {
    mergeFieldErrors(fieldErrors, { _form: normalizeFieldErrorValue(d.errors) });
  }

  const detailParsed = parseDetail(d.detail);
  mergeFieldErrors(fieldErrors, detailParsed);
  if (detailParsed._form && !fieldErrors._form) {
    fieldErrors._form = detailParsed._form;
  }

  const err = d.error;
  if (typeof err === "string") {
    formLevel = inferMessageFromHint(err);
  } else if (isPlainObject(err)) {
    const ne = err as ApiNestedError;
    if (typeof ne.message === "string") {
      formLevel = inferMessageFromHint(ne.message);
    }
    if (typeof ne.code === "string") {
      const byCode = mapErrorCode(ne.code);
      if (byCode) formLevel = byCode;
    }
    if (isPlainObject(ne.errors)) {
      mergeFieldErrors(fieldErrors, parseErrorsRecord(ne.errors as Record<string, unknown>));
    }
    if (isPlainObject(ne.details)) {
      mergeFieldErrors(fieldErrors, parseErrorsRecord(ne.details as Record<string, unknown>));
    }
  }

  if (typeof d.message === "string" && !formLevel) {
    formLevel = inferMessageFromHint(d.message);
  }

  return { fieldErrors, formLevel };
}

function getAxiosResponse(error: unknown): AxiosError<ApiErrorResponse>["response"] | undefined {
  if (axios.isAxiosError(error)) {
    return error.response;
  }
  if (error instanceof Error && "isAxiosError" in error && (error as AxiosError).isAxiosError) {
    return (error as AxiosError<ApiErrorResponse>).response;
  }
  return undefined;
}

/**
 * Parses API error response and extracts field-level errors
 */
export function parseApiError(error: unknown): ParsedApiError {
  const result: ParsedApiError = {
    generalMessage: DEFAULT_GENERAL,
    fieldErrors: {},
  };

  const response = getAxiosResponse(error);

  if (!response) {
    if (error instanceof Error) {
      result.generalMessage = "Unable to connect to the server. Check your connection and try again.";
    }
    return result;
  }

  const { status, data } = response;
  const extracted = extractFieldErrorsFromBody(data);
  Object.assign(result.fieldErrors, extracted.fieldErrors);

  const validationSummary =
    "Some information could not be accepted. Please review the highlighted fields below.";

  if (status === 400 || status === 422) {
    result.generalMessage = validationSummary;
    if (extracted.formLevel && Object.keys(result.fieldErrors).length === 0) {
      result.generalMessage = extracted.formLevel;
    }
  } else if (status === 401) {
    result.generalMessage = "Authentication is required. Sign in and try again.";
  } else if (status === 403) {
    result.generalMessage = "You do not have permission to perform this action.";
  } else if (status === 404) {
    result.generalMessage = "The requested resource was not found.";
  } else if (status === 409) {
    result.generalMessage = ERROR_MESSAGES.duplicate_inquiry;
  } else if (status === 429) {
    result.generalMessage = "Too many attempts. Please wait a moment and try again.";
  } else if (status >= 500) {
    result.generalMessage = "The server had a problem. Please try again in a few minutes.";
  } else if (status >= 400 && status < 500) {
    result.generalMessage =
      Object.keys(result.fieldErrors).length > 0
        ? validationSummary
        : extracted.formLevel ?? "We could not complete this request. Please check your input and try again.";
  }

  if (result.fieldErrors._form) {
    const formOnly = result.fieldErrors._form;
    delete result.fieldErrors._form;
    if (Object.keys(result.fieldErrors).length === 0) {
      result.generalMessage = formOnly;
    }
  }

  return result;
}

/**
 * Handles API error and sets form field errors using react-hook-form
 */
export function handleApiError<T extends FieldValues>(
  error: unknown,
  setError: UseFormSetError<T>,
  showToast: (message: string) => void,
  formFields?: string[]
): void {
  const parsedError = parseApiError(error);

  let hasFieldErrors = false;
  Object.entries(parsedError.fieldErrors).forEach(([field, message]) => {
    if (!formFields || formFields.includes(field)) {
      setError(field as Path<T>, {
        type: "server",
        message,
      });
      hasFieldErrors = true;
    }
  });

  showToast(parsedError.generalMessage);
}