import { Injectable, Logger } from "@nestjs/common";
import { InjectModel } from "@nestjs/mongoose";
import { isAxiosError, type AxiosResponse } from "axios";
import { randomBytes } from "node:crypto";
import { Model, Types } from "mongoose";
import {
  FanavaranAuditLog,
  FanavaranAuditLogDocument,
  FanavaranAuditStatus,
  FanavaranAuditStep,
} from "./schema/fanavaran-audit-log.schema";
import type { FanavaranAuditSession } from "./fanavaran-audit.types";

export interface RecordFanavaranAuditStepInput {
  session: FanavaranAuditSession;
  step: FanavaranAuditStep;
  status: FanavaranAuditStatus;
  requestUrl?: string;
  requestMethod?: string;
  httpStatus?: number;
  requestHeaders?: Record<string, unknown>;
  requestBody?: unknown;
  requestMeta?: Record<string, unknown>;
  responseHeaders?: Record<string, unknown>;
  responseBody?: unknown;
  responseMeta?: Record<string, unknown>;
  errorMessage?: string;
  errorDetails?: Record<string, unknown>;
  durationMs?: number;
}

export interface FanavaranHttpExchange {
  httpStatus?: number;
  requestHeaders?: Record<string, unknown>;
  responseHeaders?: Record<string, unknown>;
  responseBody?: unknown;
}

@Injectable()
export class FanavaranAuditService {
  private readonly logger = new Logger(FanavaranAuditService.name);

  /** Max serialized chars kept for request/response bodies in audit docs. */
  static readonly BODY_MAX_CHARS = 80_000;

  private static readonly SENSITIVE_HEADER_KEYS = new Set([
    "password",
    "secret",
    "authorization",
    "authenticationtoken",
    "apptoken",
    "app-token",
    "x-api-key",
    "cookie",
    "set-cookie",
  ]);

  private static readonly SENSITIVE_BODY_KEYS = new Set([
    "password",
    "secret",
    "authenticationtoken",
    "apptoken",
    "token",
    "files",
  ]);

  constructor(
    @InjectModel(FanavaranAuditLog.name)
    private readonly auditModel: Model<FanavaranAuditLogDocument>,
  ) {}

  generateTrackingCode(): string {
    const date = new Date().toISOString().slice(0, 10).replace(/-/g, "");
    const suffix = randomBytes(3).toString("hex").toUpperCase();
    return `FNV-${date}-${suffix}`;
  }

  maskNationalCode(nationalCode: string): string {
    const trimmed = nationalCode.trim();
    if (trimmed.length <= 4) {
      return "****";
    }
    return `${trimmed.slice(0, 3)}****${trimmed.slice(-2)}`;
  }

  maskToken(value: string): string {
    const trimmed = value.trim();
    if (trimmed.length <= 8) {
      return "****";
    }
    return `${trimmed.slice(0, 4)}…${trimmed.slice(-4)} (len=${trimmed.length})`;
  }

  sanitizeHeaders(
    headers?: Record<string, unknown> | null,
  ): Record<string, unknown> | undefined {
    if (!headers || typeof headers !== "object") {
      return undefined;
    }
    const out: Record<string, unknown> = {};
    for (const [rawKey, rawValue] of Object.entries(headers)) {
      if (rawValue === undefined) continue;
      const key = String(rawKey);
      const lower = key.toLowerCase();
      if (FanavaranAuditService.SENSITIVE_HEADER_KEYS.has(lower)) {
        out[key] =
          typeof rawValue === "string"
            ? this.maskToken(rawValue)
            : "***";
        continue;
      }
      if (
        typeof rawValue === "string" ||
        typeof rawValue === "number" ||
        typeof rawValue === "boolean" ||
        rawValue === null
      ) {
        out[key] = rawValue;
      } else {
        out[key] = String(rawValue);
      }
    }
    return out;
  }

  sanitizeBody(body: unknown): unknown {
    if (body === undefined) {
      return undefined;
    }
    const masked = this.maskSensitiveDeep(body);
    try {
      const serialized = JSON.stringify(masked);
      if (serialized.length <= FanavaranAuditService.BODY_MAX_CHARS) {
        return masked;
      }
      return {
        _truncated: true,
        maxChars: FanavaranAuditService.BODY_MAX_CHARS,
        preview: serialized.slice(0, FanavaranAuditService.BODY_MAX_CHARS),
      };
    } catch {
      const asString = String(masked);
      return asString.length <= FanavaranAuditService.BODY_MAX_CHARS
        ? asString
        : {
            _truncated: true,
            preview: asString.slice(0, FanavaranAuditService.BODY_MAX_CHARS),
          };
    }
  }

  /**
   * Extract request/response headers + body from an Axios response or Axios
   * error (uses `config.headers` when present). Values are returned raw;
   * `recordStep` applies sanitisation before persistence.
   */
  captureAxiosExchange(
    source: unknown,
    overrideRequestHeaders?: Record<string, unknown>,
  ): FanavaranHttpExchange {
    const toPlainHeaders = (
      headers?: Record<string, unknown> | null,
    ): Record<string, unknown> | undefined => {
      if (!headers || typeof headers !== "object") return undefined;
      const out: Record<string, unknown> = {};
      for (const [key, value] of Object.entries(headers)) {
        if (value === undefined) continue;
        out[key] =
          typeof value === "string" ||
          typeof value === "number" ||
          typeof value === "boolean" ||
          value === null
            ? value
            : String(value);
      }
      return out;
    };

    if (isAxiosError(source)) {
      return {
        httpStatus: source.response?.status,
        requestHeaders: toPlainHeaders(
          overrideRequestHeaders ??
            (source.config?.headers as Record<string, unknown> | undefined),
        ),
        responseHeaders: toPlainHeaders(
          source.response?.headers as Record<string, unknown> | undefined,
        ),
        responseBody: source.response?.data,
      };
    }

    const response = source as AxiosResponse | null;
    if (
      response &&
      typeof response === "object" &&
      "status" in response &&
      "headers" in response
    ) {
      return {
        httpStatus: response.status,
        requestHeaders: toPlainHeaders(
          overrideRequestHeaders ??
            (response.config?.headers as Record<string, unknown> | undefined),
        ),
        responseHeaders: toPlainHeaders(
          response.headers as Record<string, unknown> | undefined,
        ),
        responseBody: response.data,
      };
    }

    return {
      requestHeaders: toPlainHeaders(overrideRequestHeaders),
    };
  }

  sanitizeErrorDetails(error: unknown): Record<string, unknown> {
    if (isAxiosError(error)) {
      const data = error.response?.data;
      return {
        type: "axios",
        status: error.response?.status,
        statusText: error.response?.statusText,
        data: this.sanitizeBody(
          typeof data === "object" && data !== null
            ? data
            : typeof data === "string"
              ? data.slice(0, 2000)
              : data,
        ),
      };
    }
    if (error instanceof Error) {
      return { type: "error", name: error.name, message: error.message };
    }
    return { type: "unknown", value: String(error) };
  }

  extractErrorMessage(error: unknown): string {
    if (isAxiosError(error)) {
      const data = error.response?.data as
        | { Message?: string; message?: string }
        | string
        | undefined;
      if (typeof data === "string") {
        return data;
      }
      return (
        data?.Message ||
        data?.message ||
        error.message ||
        "Fanavaran request failed"
      );
    }
    if (error instanceof Error) {
      return error.message;
    }
    return "Fanavaran request failed";
  }

  formatErrorWithTrackingCode(message: string, trackingCode?: string): string {
    if (!trackingCode) {
      return message;
    }
    return `${message} (trackingCode: ${trackingCode})`;
  }

  async recordStep(input: RecordFanavaranAuditStepInput): Promise<void> {
    try {
      await this.auditModel.create({
        trackingCode: input.session.trackingCode,
        step: input.step,
        status: input.status,
        clientKey: input.session.clientKey,
        source: input.session.source,
        ...(input.session.claimCaseId
          ? { claimCaseId: new Types.ObjectId(input.session.claimCaseId) }
          : {}),
        ...(input.session.claimRequestId
          ? { claimRequestId: new Types.ObjectId(input.session.claimRequestId) }
          : {}),
        requestUrl: input.requestUrl,
        requestMethod: input.requestMethod,
        httpStatus: input.httpStatus,
        requestHeaders: this.sanitizeHeaders(input.requestHeaders),
        requestBody: this.sanitizeBody(input.requestBody),
        requestMeta: input.requestMeta,
        responseHeaders: this.sanitizeHeaders(input.responseHeaders),
        responseBody: this.sanitizeBody(input.responseBody),
        responseMeta: input.responseMeta,
        errorMessage: input.errorMessage,
        errorDetails: input.errorDetails,
        durationMs: input.durationMs,
      });
    } catch (error) {
      this.logger.error(
        `Failed to persist Fanavaran audit step ${input.step} (${input.status})`,
        error,
      );
    }
  }

  async findByTrackingCode(trackingCode: string) {
    return this.auditModel
      .find({ trackingCode })
      .sort({ createdAt: 1 })
      .lean()
      .exec();
  }

  private maskSensitiveDeep(value: unknown, depth = 0): unknown {
    if (depth > 8) {
      return "[max-depth]";
    }
    if (value === null || value === undefined) {
      return value;
    }
    if (Array.isArray(value)) {
      return value.map((item) => this.maskSensitiveDeep(item, depth + 1));
    }
    if (typeof value === "object") {
      const out: Record<string, unknown> = {};
      for (const [key, child] of Object.entries(
        value as Record<string, unknown>,
      )) {
        if (FanavaranAuditService.SENSITIVE_BODY_KEYS.has(key.toLowerCase())) {
          out[key] =
            typeof child === "string" ? this.maskToken(child) : "[redacted]";
          continue;
        }
        out[key] = this.maskSensitiveDeep(child, depth + 1);
      }
      return out;
    }
    return value;
  }
}