import { createServer } from "node:http";
import { randomUUID } from "node:crypto";

import { DEV_ENDPOINT, ENVIRONMENT_DEV, ERROR_CODES } from "../protocol/index.mjs";
import {
  AUDIT_FIELD_NAMES,
  CLOUD_API_SERVICE_ID,
  createAuditRecord
} from "../audit/index.mjs";
import {
  SUPPORTED_RPC_METHODS,
  createErrorEnvelope,
  handleJsonRpcRequest
} from "./json-rpc.mjs";

const DEFAULT_BODY_LIMIT_BYTES = 1024 * 1024;

export function createCloudApiServer(options = {}) {
  return createServer(async (request, response) => {
    try {
      await routeRequest(request, response, options);
    } catch (error) {
      sendJson(response, 500, {
        error: {
          code: "internal_error",
          message: "hwlab-cloud-api request handling failed",
          reason: error.message
        }
      });
    }
  });
}

export function buildHealthPayload() {
  const serviceId = CLOUD_API_SERVICE_ID;
  const commitId = process.env.HWLAB_COMMIT_ID || process.env.HWLAB_GIT_SHA || "unknown";
  const imageReference = process.env.HWLAB_IMAGE || "unknown";
  const imageTag = process.env.HWLAB_IMAGE_TAG || commitId.slice(0, 7) || "unknown";

  return {
    serviceId,
    environment: ENVIRONMENT_DEV,
    status: "ok",
    service: {
      id: serviceId,
      role: "cloud-api",
      healthPath: "/health",
      livePath: "/health/live"
    },
    commit: {
      id: commitId,
      source: process.env.HWLAB_BUILD_SOURCE || "runtime-env"
    },
    image: {
      reference: imageReference,
      tag: imageTag,
      digest: process.env.HWLAB_IMAGE_DIGEST || "unknown"
    },
    endpoint: process.env.HWLAB_PUBLIC_ENDPOINT || DEV_ENDPOINT,
    observedAt: new Date().toISOString(),
    db: {
      connected: false,
      mode: "not_configured"
    }
  };
}

async function routeRequest(request, response, options) {
  const url = new URL(request.url || "/", "http://hwlab-cloud-api.local");

  if (request.method === "GET" && (url.pathname === "/health" || url.pathname === "/health/live")) {
    sendJson(response, 200, buildHealthPayload());
    return;
  }

  if (request.method === "GET" && url.pathname === "/live") {
    sendJson(response, 200, {
      serviceId: CLOUD_API_SERVICE_ID,
      status: "live"
    });
    return;
  }

  if (request.method === "POST" && (url.pathname === "/rpc" || url.pathname === "/json-rpc")) {
    await handleRpcHttpRequest(request, response, options);
    return;
  }

  if (url.pathname === "/v1" || url.pathname.startsWith("/v1/")) {
    await handleRestAdapter(request, response, url, options);
    return;
  }

  sendRestError(request, response, 404, "not_found", "Route is not part of the L1 cloud-api skeleton", {
    operation: `${request.method || "GET"} ${url.pathname}`,
    target: {
      type: "route",
      id: url.pathname
    }
  });
}

async function handleRpcHttpRequest(request, response, options) {
  const body = await readBody(request, options.bodyLimitBytes);
  let envelope;

  try {
    envelope = body ? JSON.parse(body) : {};
  } catch (error) {
    sendJson(
      response,
      400,
      createErrorEnvelope({
        id: "req_unassigned",
        code: ERROR_CODES.parseError,
        message: "Invalid JSON body",
        data: {
          reason: error.message
        },
        context: {
          operation: "json_rpc.parse",
          target: {
            type: "http_route",
            id: request.url || "/rpc"
          },
          result: "rejected"
        }
      })
    );
    return;
  }

  const rpcResponse = await handleJsonRpcRequest(envelope, {
    adapter: "json-rpc"
  });
  sendJson(response, statusForRpcResponse(rpcResponse), rpcResponse);
}

async function handleRestAdapter(request, response, url, options) {
  if (request.method === "GET" && url.pathname === "/v1") {
    sendJson(response, 200, {
      serviceId: CLOUD_API_SERVICE_ID,
      adapter: "rest",
      status: "skeleton",
      rpcBridge: "POST /v1/rpc/{method}",
      methods: SUPPORTED_RPC_METHODS,
      auditFields: AUDIT_FIELD_NAMES,
      db: {
        connected: false,
        mode: "not_configured"
      }
    });
    return;
  }

  if (request.method !== "POST" || !url.pathname.startsWith("/v1/rpc/")) {
    sendRestError(request, response, 404, "not_found", "REST route is not implemented in the L1 skeleton", {
      operation: `${request.method || "GET"} ${url.pathname}`,
      target: {
        type: "route",
        id: url.pathname
      }
    });
    return;
  }

  const method = decodeURIComponent(url.pathname.slice("/v1/rpc/".length));
  const body = await readBody(request, options.bodyLimitBytes);
  let params = {};

  try {
    params = body ? JSON.parse(body) : {};
  } catch (error) {
    sendRestError(request, response, 400, "parse_error", "Invalid JSON body", {
      operation: method,
      target: {
        type: "rpc_method",
        id: method
      },
      result: "rejected",
      reason: error.message
    });
    return;
  }

  if (!params || typeof params !== "object" || Array.isArray(params)) {
    sendRestError(request, response, 400, "invalid_params", "REST RPC bridge body must be a JSON object", {
      operation: method,
      target: {
        type: "rpc_method",
        id: method
      },
      result: "rejected"
    });
    return;
  }

  const rpcResponse = await handleJsonRpcRequest(
    {
      jsonrpc: "2.0",
      id: getHeader(request, "x-request-id") || `req_${randomUUID()}`,
      method,
      params,
      meta: {
        traceId: getHeader(request, "x-trace-id") || `trc_${randomUUID()}`,
        actorId: getHeader(request, "x-actor-id"),
        serviceId: getHeader(request, "x-source-service-id") || CLOUD_API_SERVICE_ID,
        environment: ENVIRONMENT_DEV
      }
    },
    {
      adapter: "rest"
    }
  );

  sendJson(response, statusForRpcResponse(rpcResponse), rpcResponse);
}

function sendRestError(request, response, statusCode, code, message, context = {}) {
  const requestId = getHeader(request, "x-request-id") || "req_unassigned";
  sendJson(response, statusCode, {
    error: {
      code,
      message,
      reason: context.reason,
      audit: createAuditRecord({
        requestId,
        actor: {
          type: "user",
          id: getHeader(request, "x-actor-id") || `system_${CLOUD_API_SERVICE_ID}`
        },
        source: {
          serviceId: CLOUD_API_SERVICE_ID,
          environment: ENVIRONMENT_DEV,
          traceId: getHeader(request, "x-trace-id"),
          adapter: "rest"
        },
        operation: context.operation || `${request.method || "GET"} ${request.url || "/"}`,
        target: context.target || {
          type: "route",
          id: request.url || "/"
        },
        result: context.result || "failed"
      })
    }
  });
}

function statusForRpcResponse(rpcResponse) {
  if (!rpcResponse.error) {
    return 200;
  }

  if (rpcResponse.error.code === ERROR_CODES.invalidRequest || rpcResponse.error.code === ERROR_CODES.parseError) {
    return 400;
  }

  if (rpcResponse.error.code === ERROR_CODES.methodNotFound) {
    return 404;
  }

  return 200;
}

function readBody(request, limitBytes = DEFAULT_BODY_LIMIT_BYTES) {
  const limit = Number.isInteger(limitBytes) && limitBytes > 0 ? limitBytes : DEFAULT_BODY_LIMIT_BYTES;

  return new Promise((resolve, reject) => {
    let body = "";
    request.setEncoding("utf8");

    request.on("data", (chunk) => {
      body += chunk;
      if (Buffer.byteLength(body, "utf8") > limit) {
        request.destroy(new Error(`request body exceeds ${limit} bytes`));
      }
    });

    request.on("end", () => resolve(body));
    request.on("error", reject);
  });
}

function sendJson(response, statusCode, body) {
  response.writeHead(statusCode, {
    "content-type": "application/json; charset=utf-8",
    "cache-control": "no-store"
  });
  response.end(`${JSON.stringify(body)}\n`);
}

function getHeader(request, name) {
  const value = request.headers[name.toLowerCase()];
  if (Array.isArray(value)) {
    return value[0];
  }
  return value;
}