/* Copyright 2017 Andrew Dawson
 *
 * This file is a part of Tusky.
 *
 * This program is free software; you can redistribute it and/or modify it under the terms of the
 * GNU General Public License as published by the Free Software Foundation; either version 3 of the
 * License, or (at your option) any later version.
 *
 * Tusky is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even
 * the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
 * Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along with Tusky; if not,
 * see <http://www.gnu.org/licenses>. */

package com.keylesspalace.tusky

import android.content.ActivityNotFoundException
import android.content.Context
import android.content.Intent
import android.content.SharedPreferences
import android.net.Uri
import android.os.Bundle
import android.text.method.LinkMovementMethod
import android.util.Log
import android.view.View
import android.widget.TextView
import androidx.appcompat.app.AlertDialog
import androidx.browser.customtabs.CustomTabColorSchemeParams
import androidx.browser.customtabs.CustomTabsIntent
import com.bumptech.glide.Glide
import com.keylesspalace.tusky.databinding.ActivityLoginBinding
import com.keylesspalace.tusky.di.Injectable
import com.keylesspalace.tusky.entity.AccessToken
import com.keylesspalace.tusky.entity.AppCredentials
import com.keylesspalace.tusky.network.MastodonApi
import com.keylesspalace.tusky.util.ThemeUtils
import com.keylesspalace.tusky.util.getNonNullString
import com.keylesspalace.tusky.util.viewBinding
import okhttp3.HttpUrl
import retrofit2.Call
import retrofit2.Callback
import retrofit2.Response
import javax.inject.Inject

class LoginActivity : BaseActivity(), Injectable {

    @Inject
    lateinit var mastodonApi: MastodonApi

    private val binding by viewBinding(ActivityLoginBinding::inflate)

    private lateinit var preferences: SharedPreferences

    private val oauthRedirectUri: String
        get() {
            val scheme = getString(R.string.oauth_scheme)
            val host = BuildConfig.APPLICATION_ID
            return "$scheme://$host/"
        }

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        setContentView(binding.root)

        if (savedInstanceState == null && BuildConfig.CUSTOM_INSTANCE.isNotBlank() && !isAdditionalLogin()) {
            binding.domainEditText.setText(BuildConfig.CUSTOM_INSTANCE)
            binding.domainEditText.setSelection(BuildConfig.CUSTOM_INSTANCE.length)
        }

        if (BuildConfig.CUSTOM_LOGO_URL.isNotBlank()) {
            Glide.with(binding.loginLogo)
                .load(BuildConfig.CUSTOM_LOGO_URL)
                .placeholder(null)
                .into(binding.loginLogo)
        }

        preferences = getSharedPreferences(
            getString(R.string.preferences_file_key), Context.MODE_PRIVATE
        )

        binding.loginButton.setOnClickListener { onButtonClick() }

        binding.whatsAnInstanceTextView.setOnClickListener {
            val dialog = AlertDialog.Builder(this)
                .setMessage(R.string.dialog_whats_an_instance)
                .setPositiveButton(R.string.action_close, null)
                .show()
            val textView = dialog.findViewById<TextView>(android.R.id.message)
            textView?.movementMethod = LinkMovementMethod.getInstance()
        }

        if (isAdditionalLogin()) {
            setSupportActionBar(binding.toolbar)
            supportActionBar?.setDisplayHomeAsUpEnabled(true)
            supportActionBar?.setDisplayShowTitleEnabled(false)
        } else {
            binding.toolbar.visibility = View.GONE
        }
    }

    override fun requiresLogin(): Boolean {
        return false
    }

    override fun finish() {
        super.finish()
        if (isAdditionalLogin()) {
            overridePendingTransition(R.anim.slide_from_left, R.anim.slide_to_right)
        }
    }

    /**
     * Obtain the oauth client credentials for this app. This is only necessary the first time the
     * app is run on a given server instance. So, after the first authentication, they are
     * saved in SharedPreferences and every subsequent run they are simply fetched from there.
     */
    private fun onButtonClick() {

        binding.loginButton.isEnabled = false

        val domain = canonicalizeDomain(binding.domainEditText.text.toString())

        try {
            HttpUrl.Builder().host(domain).scheme("https").build()
        } catch (e: IllegalArgumentException) {
            setLoading(false)
            binding.domainTextInputLayout.error = getString(R.string.error_invalid_domain)
            return
        }

        val callback = object : Callback<AppCredentials> {
            override fun onResponse(
                call: Call<AppCredentials>,
                response: Response<AppCredentials>
            ) {
                if (!response.isSuccessful) {
                    binding.loginButton.isEnabled = true
                    binding.domainTextInputLayout.error = getString(R.string.error_failed_app_registration)
                    setLoading(false)
                    Log.e(TAG, "App authentication failed. " + response.message())
                    return
                }
                val credentials = response.body()
                val clientId = credentials!!.clientId
                val clientSecret = credentials.clientSecret

                preferences.edit()
                    .putString("domain", domain)
                    .putString("clientId", clientId)
                    .putString("clientSecret", clientSecret)
                    .apply()

                redirectUserToAuthorizeAndLogin(domain, clientId)
            }

            override fun onFailure(call: Call<AppCredentials>, t: Throwable) {
                binding.loginButton.isEnabled = true
                binding.domainTextInputLayout.error = getString(R.string.error_failed_app_registration)
                setLoading(false)
                Log.e(TAG, Log.getStackTraceString(t))
            }
        }

        mastodonApi
            .authenticateApp(
                domain, getString(R.string.app_name), oauthRedirectUri,
                OAUTH_SCOPES, getString(R.string.tusky_website)
            )
            .enqueue(callback)
        setLoading(true)
    }

    private fun redirectUserToAuthorizeAndLogin(domain: String, clientId: String) {
        /* To authorize this app and log in it's necessary to redirect to the domain given,
         * login there, and the server will redirect back to the app with its response. */
        val endpoint = MastodonApi.ENDPOINT_AUTHORIZE
        val parameters = mapOf(
            "client_id" to clientId,
            "redirect_uri" to oauthRedirectUri,
            "response_type" to "code",
            "scope" to OAUTH_SCOPES
        )
        val url = "https://" + domain + endpoint + "?" + toQueryString(parameters)
        val uri = Uri.parse(url)
        if (!openInCustomTab(uri, this)) {
            val viewIntent = Intent(Intent.ACTION_VIEW, uri)
            if (viewIntent.resolveActivity(packageManager) != null) {
                startActivity(viewIntent)
            } else {
                binding.domainEditText.error = getString(R.string.error_no_web_browser_found)
                setLoading(false)
            }
        }
    }

    override fun onStart() {
        super.onStart()
        /* Check if we are resuming during authorization by seeing if the intent contains the
         * redirect that was given to the server. If so, its response is here! */
        val uri = intent.data
        val redirectUri = oauthRedirectUri

        if (uri != null && uri.toString().startsWith(redirectUri)) {
            // This should either have returned an authorization code or an error.
            val code = uri.getQueryParameter("code")
            val error = uri.getQueryParameter("error")

            /* restore variables from SharedPreferences */
            val domain = preferences.getNonNullString(DOMAIN, "")
            val clientId = preferences.getNonNullString(CLIENT_ID, "")
            val clientSecret = preferences.getNonNullString(CLIENT_SECRET, "")

            if (code != null && domain.isNotEmpty() && clientId.isNotEmpty() && clientSecret.isNotEmpty()) {

                setLoading(true)
                /* Since authorization has succeeded, the final step to log in is to exchange
                 * the authorization code for an access token. */
                val callback = object : Callback<AccessToken> {
                    override fun onResponse(call: Call<AccessToken>, response: Response<AccessToken>) {
                        if (response.isSuccessful) {
                            onLoginSuccess(response.body()!!.accessToken, domain)
                        } else {
                            setLoading(false)
                            binding.domainTextInputLayout.error = getString(R.string.error_retrieving_oauth_token)
                            Log.e(TAG, "%s %s".format(getString(R.string.error_retrieving_oauth_token), response.message()))
                        }
                    }

                    override fun onFailure(call: Call<AccessToken>, t: Throwable) {
                        setLoading(false)
                        binding.domainTextInputLayout.error = getString(R.string.error_retrieving_oauth_token)
                        Log.e(TAG, "%s %s".format(getString(R.string.error_retrieving_oauth_token), t.message))
                    }
                }

                mastodonApi.fetchOAuthToken(
                    domain, clientId, clientSecret, redirectUri, code,
                    "authorization_code"
                ).enqueue(callback)
            } else if (error != null) {
                /* Authorization failed. Put the error response where the user can read it and they
                 * can try again. */
                setLoading(false)
                binding.domainTextInputLayout.error = getString(R.string.error_authorization_denied)
                Log.e(TAG, "%s %s".format(getString(R.string.error_authorization_denied), error))
            } else {
                // This case means a junk response was received somehow.
                setLoading(false)
                binding.domainTextInputLayout.error = getString(R.string.error_authorization_unknown)
            }
        } else {
            // first show or user cancelled login
            setLoading(false)
        }
    }

    private fun setLoading(loadingState: Boolean) {
        if (loadingState) {
            binding.loginLoadingLayout.visibility = View.VISIBLE
            binding.loginInputLayout.visibility = View.GONE
        } else {
            binding.loginLoadingLayout.visibility = View.GONE
            binding.loginInputLayout.visibility = View.VISIBLE
            binding.loginButton.isEnabled = true
        }
    }

    private fun isAdditionalLogin(): Boolean {
        return intent.getBooleanExtra(LOGIN_MODE, false)
    }

    private fun onLoginSuccess(accessToken: String, domain: String) {

        setLoading(true)

        accountManager.addAccount(accessToken, domain)

        val intent = Intent(this, MainActivity::class.java)
        intent.flags = Intent.FLAG_ACTIVITY_NEW_TASK or Intent.FLAG_ACTIVITY_CLEAR_TASK
        startActivity(intent)
        finish()
        overridePendingTransition(R.anim.explode, R.anim.explode)
    }

    companion object {
        private const val TAG = "LoginActivity" // logging tag
        private const val OAUTH_SCOPES = "read write follow"
        private const val LOGIN_MODE = "LOGIN_MODE"
        private const val DOMAIN = "domain"
        private const val CLIENT_ID = "clientId"
        private const val CLIENT_SECRET = "clientSecret"

        @JvmStatic
        fun getIntent(context: Context, mode: Boolean): Intent {
            val loginIntent = Intent(context, LoginActivity::class.java)
            loginIntent.putExtra(LOGIN_MODE, mode)
            return loginIntent
        }

        /** Make sure the user-entered text is just a fully-qualified domain name.  */
        private fun canonicalizeDomain(domain: String): String {
            // Strip any schemes out.
            var s = domain.replaceFirst("http://", "")
            s = s.replaceFirst("https://", "")
            // If a username was included (e.g. username@example.com), just take what's after the '@'.
            val at = s.lastIndexOf('@')
            if (at != -1) {
                s = s.substring(at + 1)
            }
            return s.trim { it <= ' ' }
        }

        /**
         * Chain together the key-value pairs into a query string, for either appending to a URL or
         * as the content of an HTTP request.
         */
        private fun toQueryString(parameters: Map<String, String>): String {
            val s = StringBuilder()
            var between = ""
            for ((key, value) in parameters) {
                s.append(between)
                s.append(Uri.encode(key))
                s.append("=")
                s.append(Uri.encode(value))
                between = "&"
            }
            return s.toString()
        }

        private fun openInCustomTab(uri: Uri, context: Context): Boolean {

            val toolbarColor = ThemeUtils.getColor(context, R.attr.colorSurface)
            val navigationbarColor = ThemeUtils.getColor(context, android.R.attr.navigationBarColor)
            val navigationbarDividerColor = ThemeUtils.getColor(context, R.attr.dividerColor)

            val colorSchemeParams = CustomTabColorSchemeParams.Builder()
                .setToolbarColor(toolbarColor)
                .setNavigationBarColor(navigationbarColor)
                .setNavigationBarDividerColor(navigationbarDividerColor)
                .build()

            val customTabsIntent = CustomTabsIntent.Builder()
                .setDefaultColorSchemeParams(colorSchemeParams)
                .build()

            try {
                customTabsIntent.launchUrl(context, uri)
            } catch (e: ActivityNotFoundException) {
                Log.w(TAG, "Activity was not found for intent $customTabsIntent")
                return false
            }

            return true
        }
    }
}