// Emulator, an NES emulator
// Copyright (C) 2018 Sam Breadman

import Cocoa

struct Rom {
    let prg: [UInt8]
    let chr: [UInt8]
    let sram: [UInt8]
    let mapper: UInt8
    let mirror: UInt8
    let battery: UInt8
}

func loadRom(_ fileName: String) -> (Rom) {

    // Load file data
    let fileUrl = Bundle.main.url(forResource: fileName, withExtension: "nes")
    let fileData = try! Data(contentsOf: fileUrl!)

    // Load mapper type
    let mapper1: UInt8 = fileData[0x6] >> 0x4
    let mapper2: UInt8 = fileData[0x7] >> 0x4
    let mapper: UInt8 = mapper1 | (mapper2 << 0x4)

    // Load mirroring type
    let mirror1: UInt8 = fileData[0x6] & 0x1
    let mirror2: UInt8 = (fileData[0x6] >> 0x3) & 0x1
    let mirror: UInt8 = mirror1 | (mirror2 << 0x1)

    // Load battery type
    let battery: UInt8 = (fileData[0x6] >> 0x1) & 0x1

    // Load PRG-ROM banks
    let prgSize = Int(fileData[0x4]) * 0x4000
    var prg: [UInt8] = Array(repeating: 0x0, count: prgSize)
    for i in 0x0..<prgSize {
        prg[i] = fileData[0x10 + i]
    }

    // Load CHR-ROM banks
    let chrSize = Int(fileData[0x5]) * 0x2000
    var chr: [UInt8] = Array(repeating: 0x0, count: chrSize)
    for i in 0x0..<chrSize {
        chr[i] = fileData[0x10 + prgSize + i]
    }

    // Load SRAM banks
    let sram: [UInt8] = Array(repeating: 0x0, count: 0x1FFF)

    // Return data
    return Rom (
        prg: prg,
        chr: chr,
        sram: sram,
        mapper: mapper,
        mirror: mirror,
        battery: battery
    )

}

var rom = loadRom("rom")