KStarbound/src/main/kotlin/ru/dbotthepony/kstarbound/io/StarboundPak.kt

package ru.dbotthepony.kstarbound.io

import ru.dbotthepony.kstarbound.api.IVFS
import java.io.*
import java.nio.ByteBuffer
import java.nio.channels.Channels
import java.util.*
import kotlin.collections.HashMap

private fun readHeader(reader: RandomAccessFile, required: Int) {
	val read = reader.read()
	require(read == required) { "Bad Starbound Pak header, expected $required, got $read" }
}

class StarboundPakFile(
	val storage: StarboundPak,
	val name: String,
	val offset: Long,
	val length: Long
) {
	val directoryName: String
	val directoryHiearchy: Array<String>
	val fileName: String

	init {
		val split = name.substring(1).split('/').toMutableList()
		fileName = split.last()
		split.removeAt(split.size - 1)
		directoryHiearchy = split.toTypedArray()
		directoryName = split.joinToString("/")
	}

	fun read(): ByteBuffer {
		val buf = ByteBuffer.allocate(length.toInt())
		storage.reader.seek(offset)
		storage.reader.readFully(buf.array())
		return buf
	}

	override fun toString(): String {
		return name
	}

	fun readString(): String {
		return read().array().toString(Charsets.UTF_8)
	}

	companion object {
		fun read(storage: StarboundPak, reader: RandomAccessFile): StarboundPakFile {
			val readLength = reader.read()
			//val name = reader.readASCIIString(readLength).lowercase()
			val name = reader.readASCIIString(readLength)
			require(name[0] == '/') { "$name appears to be not an absolute filename" }
			val offset = reader.readLong()
			val length = reader.readLong()

			return StarboundPakFile(storage, name.intern(), offset, length)
		}

		fun read(storage: StarboundPak, reader: DataInputStream): StarboundPakFile {
			val readLength = reader.readVarInt()
			val name = reader.readASCIIString(readLength)
			require(name[0] == '/') { "$name appears to be not an absolute filename" }
			val offset = reader.readLong()
			val length = reader.readLong()

			return StarboundPakFile(storage, name.intern(), offset, length)
		}
	}
}

class StarboundPakDirectory(val name: String, val parent: StarboundPakDirectory? = null) {
	val files = HashMap<String, StarboundPakFile>()
	val directories = HashMap<String, StarboundPakDirectory>()

	fun resolve(path: Array<String>, level: Int = 0): StarboundPakDirectory {
		if (path.size == level)
			return this

		if (level == 0 && path[0] == "" && name == "/")
			return resolve(path, 1)

		if (directories.containsKey(path[level])) {
			return directories[path[level]]!!.resolve(path, level + 1)
		} else {
			val dir = StarboundPakDirectory(path[level], this)
			directories[path[level]] = dir
			return dir.resolve(path, level + 1)
		}
	}

	fun getFile(name: String) = files[name]
	fun getDirectory(name: String) = directories[name]

	fun listFiles(): Collection<StarboundPakFile> = Collections.unmodifiableCollection(files.values)
	fun listDirectories(): Collection<StarboundPakDirectory> = Collections.unmodifiableCollection(directories.values)

	fun writeFile(file: StarboundPakFile) {
		files[file.name.split('/').last()] = file
	}

	fun fullName(): String {
		var build = name
		var getParent = parent

		while (getParent != null) {
			if (getParent.parent != null) {
				build = "${getParent.name}/$build"
			} else {
				build = "/$build"
				break
			}

			getParent = getParent.parent
		}

		return build
	}

	override fun toString(): String {
		return fullName()
	}
}

class StarboundPak(val path: File, callback: (finished: Boolean, status: String) -> Unit = { _, _ -> }) : Closeable, IVFS {
	val reader = RandomAccessFile(path, "r")

	init {
		readHeader(reader, 0x53) // S
		readHeader(reader, 0x42) // B
		readHeader(reader, 0x41) // A
		readHeader(reader, 0x73) // s
		readHeader(reader, 0x73) // s
		readHeader(reader, 0x65) // e
		readHeader(reader, 0x74) // t
		readHeader(reader, 0x36) // 6
	}

	// Далее идёт 8 байтный long в формате Big Endian, который указывает на offset до INDEX
	// т.е. сделав seek(indexOffset) мы выйдем прямо на INDEX
	private val indexOffset = reader.readLong()

	init {
		reader.seek(indexOffset)

		readHeader(reader, 0x49) // I
		readHeader(reader, 0x4E) // N
		readHeader(reader, 0x44) // D
		readHeader(reader, 0x45) // E
		readHeader(reader, 0x58) // X

		callback(false, "Reading metadata")
	}

	// сразу за INDEX идут метаданные в формате Binary Json
	val metadata = BinaryJson.readObject(reader)

	// сразу за метаданными идёт количество файлов внутри данного pak в формате Big Endian variable int
	val indexNodeCount = reader.readVarLong()

	private val indexNodes = HashMap<String, StarboundPakFile>()
	val root = StarboundPakDirectory("/")

	init {
		// Сразу же за количеством файлов идут сами файлы в формате
		// byte (длинна имени файла)
		// byte[] (utf-8 имя файла)
		// long (offset от начала файла)
		// long (длинна файла)
		val stream = DataInputStream(BufferedInputStream(Channels.newInputStream(reader.channel)))

		for (i in 0 until indexNodeCount) {
			try {
				callback(false, "Reading index node $i")
				val read = StarboundPakFile.read(this, stream)

				if (read.offset > reader.length()) {
					throw IndexOutOfBoundsException("Garbage offset at index $i: ${read.offset}")
				}

				if (read.length > reader.length()) {
					throw IndexOutOfBoundsException("Garbage length at index $i: ${read.length}")
				}

				indexNodes[read.name] = read
				root.resolve(read.directoryHiearchy).writeFile(read)
			} catch (err: Throwable) {
				throw IOException("Reading index node at $i", err)
			}
		}

		callback(true, "Reading indexes finished")
	}

	override fun listFiles(path: String): Collection<String> {
		return root.resolve(path.split("/").toTypedArray()).listFiles().map { it.name }
	}

	override fun listDirectories(path: String): Collection<String> {
		return root.resolve(path.split("/").toTypedArray()).listDirectories().map { it.fullName() }
	}

	override fun pathExists(path: String): Boolean {
		return indexNodes.containsKey(path)
	}

	override fun readOrNull(path: String): ByteBuffer? {
		val node = indexNodes[path] ?: return null
		return node.read()
	}

	override fun close() {
		reader.close()
	}
}