import * as checks from "./checks.js"
import * as o from "oauth4webapi"
import {
  OAuthCallbackError,
  OAuthProfileParseError,
} from "../../../../errors.js"

import type {
  Account,
  InternalOptions,
  LoggerInstance,
  Profile,
  RequestInternal,
  TokenSet,
  User,
} from "../../../../types.js"
import { type OAuthConfigInternal } from "../../../../providers/index.js"
import type { Cookie } from "../../../utils/cookie.js"
import { isOIDCProvider } from "../../../utils/providers.js"
import { conformInternal, customFetch } from "../../../symbols.js"
import { decodeJwt } from "jose"

function formUrlEncode(token: string) {
  return encodeURIComponent(token).replace(/%20/g, "+")
}

/**
 * Formats client_id and client_secret as an HTTP Basic Authentication header as per the OAuth 2.0
 * specified in RFC6749.
 */
function clientSecretBasic(clientId: string, clientSecret: string) {
  const username = formUrlEncode(clientId)
  const password = formUrlEncode(clientSecret)
  const credentials = btoa(`${username}:${password}`)
  return `Basic ${credentials}`
}

/**
 * Handles the following OAuth steps.
 * https://www.rfc-editor.org/rfc/rfc6749#section-4.1.1
 * https://www.rfc-editor.org/rfc/rfc6749#section-4.1.3
 * https://openid.net/specs/openid-connect-core-1_0.html#UserInfoRequest
 *
 * @note Although requesting userinfo is not required by the OAuth2.0 spec,
 * we fetch it anyway. This is because we always want a user profile.
 */
export async function handleOAuth(
  params: RequestInternal["query"],
  cookies: RequestInternal["cookies"],
  options: InternalOptions<"oauth" | "oidc">
) {
  const { logger, provider } = options

  let as: o.AuthorizationServer

  const { token, userinfo } = provider
  // Falls back to authjs.dev if the user only passed params
  if (
    (!token?.url || token.url.host === "authjs.dev") &&
    (!userinfo?.url || userinfo.url.host === "authjs.dev")
  ) {
    // We assume that issuer is always defined as this has been asserted earlier

    const issuer = new URL(provider.issuer!)
    const discoveryResponse = await o.discoveryRequest(issuer, {
      [o.allowInsecureRequests]: true,
      [o.customFetch]: provider[customFetch],
    })
    as = await o.processDiscoveryResponse(issuer, discoveryResponse)

    if (!as.token_endpoint)
      throw new TypeError(
        "TODO: Authorization server did not provide a token endpoint."
      )

    if (!as.userinfo_endpoint)
      throw new TypeError(
        "TODO: Authorization server did not provide a userinfo endpoint."
      )
  } else {
    as = {
      issuer: provider.issuer ?? "https://authjs.dev", // TODO: review fallback issuer
      token_endpoint: token?.url.toString(),
      userinfo_endpoint: userinfo?.url.toString(),
    }
  }

  const client: o.Client = {
    client_id: provider.clientId,
    ...provider.client,
  }

  let clientAuth: o.ClientAuth

  switch (client.token_endpoint_auth_method) {
    // TODO: in the next breaking major version have undefined be `client_secret_post`
    case undefined:
    case "client_secret_basic":
      // TODO: in the next breaking major version use o.ClientSecretBasic() here
      clientAuth = (_as, _client, _body, headers) => {
        headers.set(
          "authorization",
          clientSecretBasic(provider.clientId, provider.clientSecret!)
        )
      }
      break
    case "client_secret_post":
      clientAuth = o.ClientSecretPost(provider.clientSecret!)
      break
    case "client_secret_jwt":
      clientAuth = o.ClientSecretJwt(provider.clientSecret!)
      break
    case "private_key_jwt":
      clientAuth = o.PrivateKeyJwt(provider.token!.clientPrivateKey!, {
        // TODO: review in the next breaking change
        [o.modifyAssertion](_header, payload) {
          payload.aud = [as.issuer, as.token_endpoint!]
        },
      })
      break
    case "none":
      clientAuth = o.None()
      break
    default:
      throw new Error("unsupported client authentication method")
  }

  const resCookies: Cookie[] = []

  const state = await checks.state.use(cookies, resCookies, options)

  let codeGrantParams: URLSearchParams
  try {
    codeGrantParams = o.validateAuthResponse(
      as,
      client,
      new URLSearchParams(params),
      provider.checks.includes("state") ? state : o.skipStateCheck
    )
  } catch (err) {
    if (err instanceof o.AuthorizationResponseError) {
      const cause = {
        providerId: provider.id,
        ...Object.fromEntries(err.cause.entries()),
      }
      logger.debug("OAuthCallbackError", cause)
      throw new OAuthCallbackError("OAuth Provider returned an error", cause)
    }
    throw err
  }

  const codeVerifier = await checks.pkce.use(cookies, resCookies, options)

  let redirect_uri = provider.callbackUrl
  if (!options.isOnRedirectProxy && provider.redirectProxyUrl) {
    redirect_uri = provider.redirectProxyUrl
  }

  let codeGrantResponse = await o.authorizationCodeGrantRequest(
    as,
    client,
    clientAuth,
    codeGrantParams,
    redirect_uri,
    codeVerifier ?? "decoy",
    {
      // TODO: move away from allowing insecure HTTP requests
      [o.allowInsecureRequests]: true,
      [o.customFetch]: (...args) => {
        if (!provider.checks.includes("pkce")) {
          args[1].body.delete("code_verifier")
        }
        return (provider[customFetch] ?? fetch)(...args)
      },
    }
  )

  if (provider.token?.conform) {
    codeGrantResponse =
      (await provider.token.conform(codeGrantResponse.clone())) ??
      codeGrantResponse
  }

  let profile: Profile = {}

  const requireIdToken = isOIDCProvider(provider)

  if (provider[conformInternal]) {
    switch (provider.id) {
      case "microsoft-entra-id":
      case "azure-ad": {
        /**
         * These providers need the authorization server metadata to be re-processed
         * based on the `id_token`'s `tid` claim
         * @see https://github.com/MicrosoftDocs/azure-docs/issues/113944
         */
        const { tid } = decodeJwt(
          (await codeGrantResponse.clone().json()).id_token
        )
        if (typeof tid === "string") {
          const tenantRe = /microsoftonline\.com\/(\w+)\/v2\.0/
          const tenantId = as.issuer?.match(tenantRe)?.[1] ?? "common"
          const issuer = new URL(as.issuer.replace(tenantId, tid))
          const discoveryResponse = await o.discoveryRequest(issuer, {
            [o.customFetch]: provider[customFetch],
          })
          as = await o.processDiscoveryResponse(issuer, discoveryResponse)
        }
        break
      }
      default:
        break
    }
  }
  const processedCodeResponse = await o.processAuthorizationCodeResponse(
    as,
    client,
    codeGrantResponse,
    {
      expectedNonce: await checks.nonce.use(cookies, resCookies, options),
      requireIdToken,
    }
  )

  const tokens: TokenSet & Pick<Account, "expires_at"> = processedCodeResponse

  if (requireIdToken) {
    const idTokenClaims = o.getValidatedIdTokenClaims(processedCodeResponse)!
    profile = idTokenClaims

    // Apple sends some of the user information in a `user` parameter as a stringified JSON.
    // It also only does so the first time the user consents to share their information.
    if (provider[conformInternal] && provider.id === "apple") {
      try {
        profile.user = JSON.parse(params?.user)
      } catch {}
    }

    if (provider.idToken === false) {
      const userinfoResponse = await o.userInfoRequest(
        as,
        client,
        processedCodeResponse.access_token,
        {
          [o.customFetch]: provider[customFetch],
          // TODO: move away from allowing insecure HTTP requests
          [o.allowInsecureRequests]: true,
        }
      )

      profile = await o.processUserInfoResponse(
        as,
        client,
        idTokenClaims.sub,
        userinfoResponse
      )
    }
  } else {
    if (userinfo?.request) {
      const _profile = await userinfo.request({ tokens, provider })
      if (_profile instanceof Object) profile = _profile
    } else if (userinfo?.url) {
      const userinfoResponse = await o.userInfoRequest(
        as,
        client,
        processedCodeResponse.access_token,
        {
          [o.customFetch]: provider[customFetch],
          // TODO: move away from allowing insecure HTTP requests
          [o.allowInsecureRequests]: true,
        }
      )
      profile = await userinfoResponse.json()
    } else {
      throw new TypeError("No userinfo endpoint configured")
    }
  }

  if (tokens.expires_in) {
    tokens.expires_at =
      Math.floor(Date.now() / 1000) + Number(tokens.expires_in)
  }

  const profileResult = await getUserAndAccount(
    profile,
    provider,
    tokens,
    logger
  )

  return { ...profileResult, profile, cookies: resCookies }
}

/**
 * Returns the user and account that is going to be created in the database.
 * @internal
 */
export async function getUserAndAccount(
  OAuthProfile: Profile,
  provider: OAuthConfigInternal<any>,
  tokens: TokenSet,
  logger: LoggerInstance
) {
  try {
    const userFromProfile = await provider.profile(OAuthProfile, tokens)
    const user = {
      ...userFromProfile,
      // The user's id is intentionally not set based on the profile id, as
      // the user should remain independent of the provider and the profile id
      // is saved on the Account already, as `providerAccountId`.
      id: crypto.randomUUID(),
      email: userFromProfile.email?.toLowerCase(),
    } satisfies User

    return {
      user,
      account: {
        ...tokens,
        provider: provider.id,
        type: provider.type,
        providerAccountId: userFromProfile.id ?? crypto.randomUUID(),
      },
    }
  } catch (e) {
    // If we didn't get a response either there was a problem with the provider
    // response *or* the user cancelled the action with the provider.
    //
    // Unfortunately, we can't tell which - at least not in a way that works for
    // all providers, so we return an empty object; the user should then be
    // redirected back to the sign up page. We log the error to help developers
    // who might be trying to debug this when configuring a new provider.
    logger.debug("getProfile error details", OAuthProfile)
    logger.error(
      new OAuthProfileParseError(e as Error, { provider: provider.id })
    )
  }
}