package io.oxygenhub.android.runner

import android.content.Context

import android.content.Intent

import android.net.ConnectivityManager

import android.net.NetworkCapabilities

import android.os.BatteryManager

import android.os.Build

import androidx.core.content.ContextCompat

import io.oxygenhub.android.api.HubApi

import kotlinx.coroutines.Dispatchers

import kotlinx.coroutines.flow.MutableStateFlow

import kotlinx.coroutines.flow.StateFlow

import kotlinx.coroutines.flow.asStateFlow

import kotlinx.coroutines.withContext

import uniffi.rust_core.runnerIsRegistered

import uniffi.rust_core.runnerRegister

import uniffi.rust_core.runnerStop

import java.io.File

/**

 * The phone as an OxygenFlow runner (#8): OxygenFlow's own runner, built

 * into the app through rust-core, offering the WASM tier. It runs in

 * [RunnerService] only while the phone is on charge and on an unmetered

 * network (Wi-Fi), and drains when either stops: it claims nothing more

 * and finishes what it holds.

 */

object PhoneRunner {

    sealed interface State {

        data object Unregistered : State

        /** Registered, not running. */

        data object Stopped : State

        /** Not allowed to run now, and why (off charge, off Wi-Fi). */

        data class Waiting(val why: String) : State

        data object Running : State

        /** Told to stop: finishing what it holds. */

        data class Draining(val why: String) : State

        data class Failed(val message: String) : State

    }

    private val _state = MutableStateFlow<State>(State.Unregistered)

    val state: StateFlow<State> = _state.asStateFlow()

    internal fun set(state: State) {

        _state.value = state

    }

    /** Where the runner keeps its credential and its jobs' files. */

    fun home(context: Context): File = File(context.filesDir, "flow").also { it.mkdirs() }

    /** Called when the app starts and the service ends: what the runner is, as far as this process knows. */

    fun refresh(context: Context) {

        val now = _state.value

        if (now is State.Running || now is State.Draining) return

        _state.value = if (runnerIsRegistered(home(context).path)) {

            if (now is State.Waiting || now is State.Failed) now else State.Stopped

        } else {

            State.Unregistered

        }

    }

    /** The runner's name on the hub: the phone's model, as runner names are written. */

    fun name(): String =

        "android-" + Build.MODEL.lowercase().replace(Regex("[^a-z0-9]+"), "-").trim('-').ifEmpty { "phone" }

    /** Ask the hub for a token and register this phone as a runner for the account's repositories. */

    suspend fun register(context: Context, api: HubApi, hub: String): String {

        val token = api.runnerToken()

        val name = withContext(Dispatchers.IO) { runnerRegister(home(context).path, hub, token.token, name()) }

        _state.value = State.Stopped

        return name

    }

    /** Why the runner may not run now, or null when it may: on charge and on Wi-Fi. */

    fun blockedBy(context: Context): String? {

        val battery = context.getSystemService(BatteryManager::class.java)

        if (battery != null && !battery.isCharging) return "the phone is not on charge"

        val net = context.getSystemService(ConnectivityManager::class.java)

        val caps = net?.activeNetwork?.let { net.getNetworkCapabilities(it) }

        if (caps == null || !caps.hasCapability(NetworkCapabilities.NET_CAPABILITY_NOT_METERED)) {

            return "the phone is not on Wi-Fi (or another unmetered network)"

        }

        return null

    }

    fun start(context: Context) {

        ContextCompat.startForegroundService(context, Intent(context, RunnerService::class.java))

    }

    /** Drain: claim nothing more, finish and report what it holds, then stop. */

    fun drain(why: String) {

        if (_state.value == State.Running) {

            _state.value = State.Draining(why)

            runnerStop()

        }

    }

}