import Fastify from "fastify"

import type { GatewayConfig } from "./config.js"
import { proxyToUpstream } from "./proxy.js"

export function createGatewayServer(config: GatewayConfig) {
  const app = Fastify({
    logger: true,
  })

  app.get("/health", async () => ({
    service: "image-platform-gateway",
    status: "ok",
  }))

  app.get<{ Params: ImageParams; Querystring: ImageQuery }>(
    "/images/:assetId/:version/:preset",
    async (request, reply) => {
      const version = parseVersionParam(request.params.version)

      if (version === null) {
        return reply.code(400).send({
          message: "image version must use v{number} format",
          statusCode: 400,
        })
      }

      const width = parseOptionalInteger(request.query.w)
      const quality = parseOptionalInteger(request.query.q)
      const format = request.query.f ?? "auto"

      return reply.code(501).header("cache-control", "no-store").send({
        assetId: request.params.assetId,
        format,
        message: "image gateway read-through pipeline is not implemented yet",
        preset: request.params.preset,
        quality,
        status: "not_implemented",
        version,
        width,
      })
    },
  )

  app.all("/api/*", async (request, reply) => proxyToUpstream(request, reply, config.backendUpstream))
  app.all("/docs", async (request, reply) => proxyToUpstream(request, reply, config.backendUpstream))
  app.all("/docs/*", async (request, reply) => proxyToUpstream(request, reply, config.backendUpstream))
  app.all("/docs-json", async (request, reply) => proxyToUpstream(request, reply, config.backendUpstream))

  app.setNotFoundHandler(async (_request, reply) => {
    return reply.code(404).send({
      message: "route not found",
      statusCode: 404,
    })
  })

  return app
}

type ImageQuery = {
  f?: string
  q?: string
  w?: string
}

type ImageParams = {
  assetId: string
  preset: string
  version: string
}

function parseVersionParam(value: string) {
  if (!value.startsWith("v")) {
    return null
  }

  const parsed = Number.parseInt(value.slice(1), 10)

  return Number.isSafeInteger(parsed) && parsed > 0 ? parsed : null
}

function parseOptionalInteger(value: string | undefined) {
  if (!value) {
    return null
  }

  const parsed = Number.parseInt(value, 10)

  return Number.isFinite(parsed) ? parsed : null
}