import * as Sentry from "@sentry/nextjs"
import deepmerge from "deepmerge"
import { flatten } from "flat"

import { logger } from "../logger"

import type { ZodError } from "zod"

/**
 * Sanitizes an input object, ensuring its values are valid OpenTelemetry
 * `AttributeValue` or `JSON.stringify()` representations as a fallback.
 * It recursively processes nested objects and flattens the final object to one
 * level deep with dot delimited keys for nested values.
 *
 * @param data The input object to sanitize.
 * @returns The resulting object.
 *
 * @example
 * ```typescript
 *
 * const input = {
 *   key1: "Example",
 *   key2: 10,
 *   nested: {
 *     nestedKey1: "Value",
 *     nestedKey2: {
 *       nestedKey2Key1: true,
 *     },
 *   },
 * };
 *
 * const sanitized = sanitize(input);
 * logger.log(sanitized);
 * // {
 * //   key1: "Example",
 * //   key2: 10,
 * //   "nested.nestedKey1": "Value",
 * //   "nested.nestedKey2.nestedKey2Key1": true,
 * // }
 * ```
 */
export function sanitize(data: any): Record<string, string | number | boolean> {
  if (!data) return {}
  if (typeof data === "string") {
    return { value: data }
  }
  return flatten(data)
}

/**
 * Creates an object that holds three OpenTelemetry counter instruments. One
 * that represents the counter itself, one for the success and one for any fail.
 * The object contains an `init method that acts as a factory to create the a
 * final object that holds methods to record different types of events one the
 * appropriate counter.
 *
 * @param meterName The name of the OpenTelemetry meter to create.
 * @param counterName The name of the counter instrument to create.
 * @returns An object with an `init` method that returns an object
 * with methods for recording counter events.
 *
 * @example
 *
 * See the codebase for reference usage.
 */

export function createCounter(meterName: string) {
  return {
    /**
     * Initializes the counter event handlers with a set of base attributes.
     * These attributes will be included in all recorded events.
     *
     * @param baseAttrs - The base attributes to associate with the counter. Defaults to an empty object.
     * @returns An object with methods to record specific counter events.
     */
    init(baseAttrs: object = {}) {
      return {
        /**
         * Records an event for the main counter.
         *
         * @param attrs - Additional attributes specific to this 'start' event. Defaults to an empty object.
         */
        start(attrs: object | undefined = undefined) {
          logger.debug(`[${meterName}] start`, attrs)
        },

        /**
         * Records an event for the success counter.
         *
         * @param attrs - Additional attributes specific to this 'success' event. Defaults to an empty object.
         */
        success(attrs: object = {}) {
          const mergedAttrs = deepmerge.all<object>([baseAttrs, attrs])
          const finalAttrs = sanitize(mergedAttrs)
          Sentry.metrics.count(meterName, 1, {
            attributes: { ...finalAttrs, status: "success" },
          })
          logger.debug(`[${meterName}] success`, mergedAttrs)
        },

        /**
         * Records an event of type `data_error` for the fail counter.
         * Used when some dependent data could not be resolved during the
         * operation. Note that "no data" also exists and might be more
         * appropriate in certain situations.
         *
         * @param errorMsg - A message describing the data error.
         * @param attrs - Additional attributes specific to this 'dataError' event. Defaults to an empty object.
         */
        dataError(errorMsg: string, attrs: object = {}) {
          const mergedAttrs = deepmerge.all<object>([
            baseAttrs,
            attrs,
            {
              error_type: "data_error",
              error: errorMsg,
            },
          ])
          const finalAttrs = sanitize(mergedAttrs)

          Sentry.metrics.count(meterName, 1, {
            attributes: { ...finalAttrs, status: "error" },
          })
          logger.error(`[${meterName}] dataError: ${errorMsg}`, mergedAttrs)
        },

        /**
         * Records an event of type `not_found` for the fail counter.
         * Used when some dependent data could not be found during the operation.
         * Note that when there is an error resolving the data, the
         * `dataError` method might be more appropriate.
         *
         * @param attrs - Additional attributes specific to this 'noDataError' event. Defaults to an empty object.
         */
        noDataError(attrs: object = {}) {
          const mergedAttrs = deepmerge.all<object>([
            baseAttrs,
            attrs,
            {
              error_type: "not_found",
            },
          ])
          const finalAttrs = sanitize(mergedAttrs)

          Sentry.metrics.count(meterName, 1, {
            attributes: { ...finalAttrs, status: "error" },
          })
          logger.error(`[${meterName}] noDataError:`, mergedAttrs)
        },

        /**
         * Records an event of type `validation_error` for the fail counter.
         * Used when a Zod schema fails validation.
         *
         * @param zodError - The {@link ZodError} object representing the validation error.
         */
        validationError(zodError: ZodError) {
          const mergedAttrs = deepmerge.all<object>([
            baseAttrs,
            {
              error_type: "validation_error",
              ...sanitize(zodError.format()),
            },
          ])
          const finalAttrs = sanitize(mergedAttrs)

          Sentry.metrics.count(meterName, 1, {
            attributes: { ...finalAttrs, status: "error" },
          })
          logger.error(`[${meterName}] validationError`, mergedAttrs)
        },

        /**
         * Records an event of type `http_error` for the fail counter.
         * Used when a `fetch(...)` call fails. **Note**: This method must be
         * `await`ed as it is asynchronous!
         * The given {@link Response} must be unprocessed and will be cloned
         * to avoid interfering with its consumption outside this function.
         *
         * @param response - The HTTP {@link Response} object.
         */
        async httpError(response: Response) {
          const res = response.clone()
          const text = await res.text()

          const mergedAttrs = deepmerge.all<object>([
            baseAttrs,
            {
              error_type: "http_error",
              "error.status": res.status,
              "error.statusText": res.statusText,
              "error.text": text,
              url: res.url,
            },
          ])
          const finalAttrs = sanitize(mergedAttrs)

          Sentry.metrics.count(meterName, 1, {
            attributes: { ...finalAttrs, status: "error" },
          })
          logger.error(
            `[${meterName}] httpError ${res.status}, ${res.statusText}:`,
            mergedAttrs
          )
        },

        /**
         * Records an event of type `error` for the fail counter.
         * Used when an error is thrown or an exception is caught, or as a
         * general-purpose way to record an 'error' on the fail counter.
         *
         * @param err - An optional error object or message associated with the
         * failure. Usually an instance of {@link Error} or a string.
         */
        fail(err?: unknown) {
          let msg = "unknown"

          if (err && err instanceof Error) {
            msg = err.message
          } else if (typeof err === "string") {
            msg = err
          }

          const mergedAttrs = deepmerge.all<object>([
            baseAttrs,
            {
              error_type: "error",
              error: msg,
            },
          ])
          const finalAttrs = sanitize(mergedAttrs)

          Sentry.metrics.count(meterName, 1, {
            attributes: { ...finalAttrs, status: "error" },
          })
          logger.error(`[${meterName}] fail message: ${msg}`, mergedAttrs)
        },
      }
    },
  }
}