import type * as cloudwatch from "@distilled.cloud/aws/cloudwatch";
import * as Effect from "effect/Effect";
import * as Layer from "effect/Layer";
import * as Binding from "../../Binding.ts";
import { makeBatchedSink } from "../internal/BatchedSink.ts";
import { isBindingHost } from "../Lambda/Function.ts";
import {
  MetricSink,
  type MetricSinkDatum,
  type MetricSinkProps,
} from "./MetricSink.ts";
import { PutMetricData } from "./PutMetricData.ts";

const encoder = new TextEncoder();

/**
 * PutMetricData accepts up to 1 MB per POST; approximate each datum's wire
 * size by its JSON encoding and leave headroom for the request envelope
 * (`Action`, `Namespace`, form-encoding overhead).
 */
const MAX_BYTES = 1_000_000;

export const MetricSinkHttp = Layer.effect(
  MetricSink,
  Effect.gen(function* () {
    const putMetricData = yield* PutMetricData;

    return Effect.fn(function* (props: MetricSinkProps) {
      if (!globalThis.__ALCHEMY_RUNTIME__) {
        const host = yield* Binding.Host;
        if (isBindingHost(host)) {
          yield* host.bind`Allow(${host}, AWS.CloudWatch.MetricSink(${props.Namespace}))`(
            {
              policyStatements: [
                {
                  Effect: "Allow",
                  // PutMetricData does not support resource-level permissions.
                  Action: ["cloudwatch:PutMetricData"],
                  Resource: ["*"],
                },
              ],
            },
          );
        }
      }
      const put = yield* putMetricData();
      return makeBatchedSink<
        MetricSinkDatum,
        cloudwatch.PutMetricDataResponse,
        cloudwatch.PutMetricDataError
      >({
        maxRecords: 1000,
        maxBytes: MAX_BYTES,
        sizeOf: (datum) => encoder.encode(JSON.stringify(datum)).length,
        send: (batch) =>
          put({
            Namespace: props.Namespace,
            MetricData: [...batch],
          }),
        // PutMetricData is all-or-nothing — no per-datum partial failures to
        // extract, so there is no `unprocessed`/`rejected` handling here.
      });
    });
  }),
);