conventionschedule-android/app/src/main/java/com/adlerosn/brasilfurfest/schedule/managers/CacheManager.kt

package com.adlerosn.brasilfurfest.schedule.managers

import android.content.Context
import com.adlerosn.brasilfurfest.helper.joinFile
import com.adlerosn.brasilfurfest.helper.lastPathPart
import java.io.File
import java.io.InputStream
import java.io.Serializable

class CacheManager(context: Context): Serializable {
    private val cacheLocation = File(context.filesDir, "cache_data")
            .also {
                if (!it.isDirectory) {
                    it.mkdirs()
                }
            }
    private val cacheStamps = File(context.filesDir, "cache_stamps")
            .also {
                if (!it.isDirectory) {
                    it.mkdirs()
                }
            }

    init {
        sanitize()
    }

    fun getStamp(file: String): String?{
        knownNeeded?.add(file)
        val cachedFile = cacheLocation.joinFile(file)
        val cachedData = cacheStamps.joinFile(file)
        if(!cachedFile.exists() || !cachedData.exists()) return null
        return cachedData.readText().let { if(it.isBlank()) null else it }
    }

    operator fun get(file: String): Pair<InputStream, String>?{
        knownNeeded?.add(file)
        val cachedFile = cacheLocation.joinFile(file)
        val cachedData = cacheStamps.joinFile(file)
        if(!cachedFile.exists() || !cachedData.exists()) return null
        val stamp = cachedData.readText()
        if(stamp.isBlank()) return null
        return Pair(
                cachedFile.inputStream(),
                stamp
        )
    }

    operator fun set(file: String, requestResult: Pair<ByteArray, String>){
        if (requestResult.second.isBlank()) return
        knownNeeded?.add(file)
        val cachedFile = cacheLocation.joinFile(file)
        val cachedData = cacheStamps.joinFile(file)
        cachedData.writeText(requestResult.second)
        cachedFile.writeBytes(requestResult.first)
    }

    fun delete(file: String): Boolean {
        val cachedFile = cacheLocation.joinFile(file)
        val cachedData = cacheStamps.joinFile(file)
        return (if (cachedFile.exists()) cachedFile.delete() else false) and (if (cachedData.exists()) cachedData.delete() else false)
    }

    fun sanitize(): Int{
        val datas = cacheLocation.listFiles().toList().map { it.absolutePath.lastPathPart() }
        val stmps = cacheStamps.listFiles().toList().map { it.absolutePath.lastPathPart() }
        val unreliableEntries = (datas-stmps) + (stmps-datas)
        return unreliableEntries.map { delete(it) }.size
    }

    val files: Set<String>
        get() {
            val datas = cacheLocation.listFiles().toList().map { it.absolutePath.lastPathPart() }
            val stmps = cacheStamps.listFiles().toList().map { it.absolutePath.lastPathPart() }
            return datas.intersect(stmps)
        }

    private var knownNeeded: MutableList<String>? = null
    fun startMonitoringNeededFiles(){ knownNeeded = mutableListOf() }
    fun removeNotNeededFiles(): Int{
        sanitize()
        if(knownNeeded==null) return 0
        val notNeeded = files - knownNeeded!!
        knownNeeded = null
        return notNeeded.map { delete(it) }.size
    }
}