/*
 * Copyright 2018 Allan Wang
 *
 * 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.
 *
 * This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.
 */
package com.pitchedapps.frost.injectors

import android.webkit.WebView
import com.pitchedapps.frost.utils.L
import com.pitchedapps.frost.web.FrostWebViewClient
import io.reactivex.Single
import io.reactivex.android.schedulers.AndroidSchedulers
import io.reactivex.disposables.Disposable
import io.reactivex.subjects.SingleSubject
import org.apache.commons.text.StringEscapeUtils
import java.util.Locale

class JsBuilder {
    private val css = StringBuilder()
    private val js = StringBuilder()

    private var tag: String? = null

    fun css(css: String): JsBuilder {
        this.css.append(StringEscapeUtils.escapeEcmaScript(css))
        return this
    }

    fun js(content: String): JsBuilder {
        this.js.append(content)
        return this
    }

    fun single(tag: String): JsBuilder {
        this.tag = "_frost_${tag.toLowerCase(Locale.CANADA)}"
        return this
    }

    fun build() = JsInjector(toString())

    override fun toString(): String {
        val tag = this.tag
        val builder = StringBuilder().apply {
            append("!function(){")
            if (css.isNotBlank()) {
                val cssMin = css.replace(Regex("\\s*\n\\s*"), "")
                append("var a=document.createElement('style');")
                append("a.innerHTML='$cssMin';")
                if (tag != null) append("a.id='$tag';")
                append("document.head.appendChild(a);")
            }
            if (js.isNotBlank())
                append(js)
        }
        var content = builder.append("}()").toString()
        if (tag != null) content = singleInjector(tag, content)
        return content
    }

    private fun singleInjector(tag: String, content: String) = StringBuilder().apply {
        append("if (!window.hasOwnProperty(\"$tag\")) {")
        append("console.log(\"Registering $tag\");")
        append("window.$tag = true;")
        append(content)
        append("}")
    }.toString()
}

/**
 * Contract for all injectors to allow it to interact properly with a webview
 */
interface InjectorContract {
    fun inject(webView: WebView) = inject(webView, null)
    fun inject(webView: WebView, callback: (() -> Unit)?)
    /**
     * Toggle the injector (usually through Prefs
     * If false, will fallback to an empty action
     */
    fun maybe(enable: Boolean): InjectorContract = if (enable) this else JsActions.EMPTY
}

/**
 * Helper method to inject multiple functions simultaneously with a single callback
 */
fun WebView.jsInject(vararg injectors: InjectorContract, callback: ((Int) -> Unit)? = null): Disposable? {
    val validInjectors = injectors.filter { it != JsActions.EMPTY }
    if (validInjectors.isEmpty()) {
        callback?.invoke(0)
        return null
    }
    L.d { "Injecting ${validInjectors.size} items" }
    if (callback == null) {
        validInjectors.forEach { it.inject(this) }
        return null
    }
    val observables = Array(validInjectors.size) { SingleSubject.create<Unit>() }
    val disposable = Single.zip<Unit, Int>(observables.asList()) { it.size }
        .observeOn(AndroidSchedulers.mainThread())
        .subscribe { res, _ ->
            callback(res)
        }
    (0 until validInjectors.size).forEach { i ->
        validInjectors[i].inject(this) {
            observables[i].onSuccess(Unit)
        }
    }
    return disposable
}

fun FrostWebViewClient.jsInject(
    vararg injectors: InjectorContract,
    callback: ((Int) -> Unit)? = null
) = web.jsInject(*injectors, callback = callback)

/**
 * Wrapper class to convert a function into an injector
 */
class JsInjector(val function: String) : InjectorContract {
    override fun inject(webView: WebView, callback: (() -> Unit)?) {
        webView.evaluateJavascript(function) { callback?.invoke() }
    }
}