DiAL/src/server/checker/expect/http.ts

import type { BodyRule, CheckFailure, HeaderExpect, HttpExpectConfig } from "../types";
import { checkBodyExpect } from "./body";
import { applyOperator } from "./body";
import { mismatchFailure, errorFailure } from "./failure";

export interface HttpObservation {
  statusCode: number;
  headers: Record<string, string>;
  body: string | null;
  durationMs: number;
}

function checkStatus(obs: HttpObservation, allowed: number[]): { matched: boolean; failure: CheckFailure | null } {
  if (!allowed.includes(obs.statusCode)) {
    return {
      matched: false,
      failure: mismatchFailure(
        "status",
        "status",
        allowed,
        obs.statusCode,
        `status ${obs.statusCode} not in [${allowed}]`,
      ),
    };
  }
  return { matched: true, failure: null };
}

function checkDuration(
  obs: HttpObservation,
  maxDurationMs?: number,
): { matched: boolean; failure: CheckFailure | null } {
  if (maxDurationMs === undefined) return { matched: true, failure: null };
  if (obs.durationMs > maxDurationMs) {
    return {
      matched: false,
      failure: mismatchFailure(
        "duration",
        "duration",
        `<=${maxDurationMs}ms`,
        obs.durationMs,
        `duration ${obs.durationMs}ms > ${maxDurationMs}ms`,
      ),
    };
  }
  return { matched: true, failure: null };
}

function checkHeaders(
  obs: HttpObservation,
  headerExpects?: Record<string, HeaderExpect>,
): { matched: boolean; failure: CheckFailure | null } {
  if (!headerExpects) return { matched: true, failure: null };

  for (const [key, expected] of Object.entries(headerExpects)) {
    const actualValue = obs.headers[key.toLowerCase()];
    const path = `headers.${key}`;

    if (typeof expected === "string") {
      if (actualValue !== expected) {
        return {
          matched: false,
          failure: mismatchFailure("headers", path, expected, actualValue, `header ${key} mismatch`),
        };
      }
    } else {
      if (actualValue === undefined) {
        if (expected.exists !== false) {
          return {
            matched: false,
            failure: mismatchFailure("headers", path, "defined", undefined, `header ${key} not found`),
          };
        }
        continue;
      }
      if (!applyOperator(actualValue, expected)) {
        return {
          matched: false,
          failure: mismatchFailure("headers", path, expected, actualValue, `header ${key} mismatch`),
        };
      }
    }
  }

  return { matched: true, failure: null };
}

function checkBody(obs: HttpObservation, bodyRules?: BodyRule[]): { matched: boolean; failure: CheckFailure | null } {
  if (!bodyRules || bodyRules.length === 0) return { matched: true, failure: null };

  if (obs.body === null) {
    return {
      matched: false,
      failure: errorFailure("body", "body", "body is null but body rules are configured"),
    };
  }

  return checkBodyExpect(obs.body, bodyRules);
}

export function checkHttpExpect(
  obs: HttpObservation,
  expect?: HttpExpectConfig,
): { matched: boolean; failure: CheckFailure | null } {
  if (!expect) {
    return checkStatus(obs, [200]);
  }

  const statusResult = checkStatus(obs, expect.status ?? [200]);
  if (!statusResult.matched) return statusResult;

  const durationResult = checkDuration(obs, expect.maxDurationMs);
  if (!durationResult.matched) return durationResult;

  const headersResult = checkHeaders(obs, expect.headers);
  if (!headersResult.matched) return headersResult;

  const bodyResult = checkBody(obs, expect.body);
  if (!bodyResult.matched) return bodyResult;

  return { matched: true, failure: null };
}