/// Struct containing everything
use std::cell::{Cell, RefCell};
use std::rc::Rc;

use bincode;
use serde::{Deserialize, Serialize};

use super::arm7tdmi;
use super::cartridge::Cartridge;
use super::dma::DmaController;
use super::gpu::*;
use super::interrupt::*;
use super::iodev::*;
use super::sched::{EventHandler, EventType, Scheduler, SharedScheduler};
use super::sound::SoundController;
use super::sysbus::SysBus;
use super::timer::Timers;
use super::util::Shared;

#[cfg(not(feature = "no_video_interface"))]
use super::VideoInterface;
use super::{AudioInterface, InputInterface};

pub struct GameBoyAdvance {
    pub cpu: arm7tdmi::Core,
    pub sysbus: Box<SysBus>,
    io_devs: Shared<IoDevices>,

    #[cfg(not(feature = "no_video_interface"))]
    pub video_device: Rc<RefCell<dyn VideoInterface>>,
    pub audio_device: Rc<RefCell<dyn AudioInterface>>,
    pub input_device: Rc<RefCell<dyn InputInterface>>,

    pub cycles_to_next_event: usize,

    scheduler: SharedScheduler,

    overshoot_cycles: usize,
    interrupt_flags: SharedInterruptFlags,
}

#[derive(Serialize, Deserialize)]
struct SaveState {
    scheduler: Scheduler,
    io_devs: IoDevices,
    cartridge: Cartridge,
    ewram: Box<[u8]>,
    iwram: Box<[u8]>,
    interrupt_flags: u16,
    cpu: arm7tdmi::Core,
}

/// Checks if the bios provided is the real one
fn check_real_bios(bios: &[u8]) -> bool {
    use sha2::{Digest, Sha256};

    let mut hasher = Sha256::new();
    hasher.input(bios);
    let digest = hasher.result();

    let expected_hash = hex!("fd2547724b505f487e6dcb29ec2ecff3af35a841a77ab2e85fd87350abd36570");

    digest.as_slice() == &expected_hash[..]
}

impl GameBoyAdvance {
    pub fn new(
        bios_rom: Box<[u8]>,
        gamepak: Cartridge,
        #[cfg(not(feature = "no_video_interface"))] video_device: Rc<RefCell<dyn VideoInterface>>,
        audio_device: Rc<RefCell<dyn AudioInterface>>,
        input_device: Rc<RefCell<dyn InputInterface>>,
    ) -> GameBoyAdvance {
        // Warn the user if the bios is not the real one
        match check_real_bios(&bios_rom) {
            true => info!("Verified bios rom"),
            false => warn!("This is not the real bios rom, some games may not be compatible"),
        };

        let interrupt_flags = Rc::new(Cell::new(IrqBitmask(0)));
        let scheduler = Scheduler::new_shared();

        let intc = InterruptController::new(interrupt_flags.clone());
        let gpu = Box::new(Gpu::new(scheduler.clone(), interrupt_flags.clone()));
        let dmac = DmaController::new(interrupt_flags.clone(), scheduler.clone());
        let timers = Timers::new(interrupt_flags.clone());
        let sound_controller = Box::new(SoundController::new(
            scheduler.clone(),
            audio_device.borrow().get_sample_rate() as f32,
        ));
        let io_devs = Shared::new(IoDevices::new(intc, gpu, dmac, timers, sound_controller));
        let sysbus = Box::new(SysBus::new(
            scheduler.clone(),
            io_devs.clone(),
            bios_rom,
            gamepak,
        ));

        let cpu = arm7tdmi::Core::new();

        let mut gba = GameBoyAdvance {
            cpu,
            sysbus,
            io_devs,

            #[cfg(not(feature = "no_video_interface"))]
            video_device: video_device,
            audio_device: audio_device,
            input_device: input_device,

            scheduler: scheduler,

            cycles_to_next_event: 1,
            overshoot_cycles: 0,
            interrupt_flags: interrupt_flags,
        };

        gba.sysbus.created();

        gba
    }

    pub fn from_saved_state(
        savestate: &[u8],
        bios: Box<[u8]>,
        rom: Box<[u8]>,
        #[cfg(not(feature = "no_video_interface"))] video_device: Rc<RefCell<dyn VideoInterface>>,
        audio_device: Rc<RefCell<dyn AudioInterface>>,
        input_device: Rc<RefCell<dyn InputInterface>>,
    ) -> bincode::Result<GameBoyAdvance> {
        let decoded: Box<SaveState> = bincode::deserialize_from(savestate)?;

        let arm7tdmi = decoded.cpu;
        let interrupts = Rc::new(Cell::new(IrqBitmask(decoded.interrupt_flags)));
        let scheduler = decoded.scheduler.make_shared();
        let mut io_devs = Shared::new(decoded.io_devs);
        let mut cartridge = decoded.cartridge;
        cartridge.set_rom_bytes(rom);
        io_devs.connect_irq(interrupts.clone());
        io_devs.gpu.set_scheduler(scheduler.clone());
        io_devs.sound.set_scheduler(scheduler.clone());

        let sysbus = Box::new(SysBus::new_with_memories(
            scheduler.clone(),
            io_devs.clone(),
            cartridge,
            bios,
            decoded.ewram,
            decoded.iwram,
        ));

        Ok(GameBoyAdvance {
            cpu: arm7tdmi,
            sysbus: sysbus,
            io_devs,

            interrupt_flags: interrupts,

            #[cfg(not(feature = "no_video_interface"))]
            video_device: video_device,
            audio_device: audio_device,
            input_device: input_device,

            cycles_to_next_event: 1,

            overshoot_cycles: 0,

            scheduler,
        })
    }

    pub fn save_state(&self) -> bincode::Result<Vec<u8>> {
        let s = SaveState {
            cpu: self.cpu.clone(),
            io_devs: self.io_devs.clone_inner(),
            cartridge: self.sysbus.cartridge.thin_copy(),
            iwram: Box::from(self.sysbus.get_iwram()),
            ewram: Box::from(self.sysbus.get_ewram()),
            interrupt_flags: self.interrupt_flags.get().value(),
            scheduler: self.scheduler.clone_inner(),
        };

        bincode::serialize(&s)
    }

    pub fn restore_state(&mut self, bytes: &[u8], bios: Box<[u8]>) -> bincode::Result<()> {
        let decoded: Box<SaveState> = bincode::deserialize_from(bytes)?;

        self.cpu = decoded.cpu;
        self.scheduler = Scheduler::make_shared(decoded.scheduler);
        self.interrupt_flags = Rc::new(Cell::new(IrqBitmask(decoded.interrupt_flags)));
        self.io_devs = Shared::new(decoded.io_devs);
        // Restore memory state
        self.sysbus.set_bios(bios);
        self.sysbus.set_iwram(decoded.iwram);
        self.sysbus.set_ewram(decoded.ewram);
        // Redistribute shared pointers
        self.io_devs.connect_irq(self.interrupt_flags.clone());
        self.io_devs.gpu.set_scheduler(self.scheduler.clone());
        self.io_devs.sound.set_scheduler(self.scheduler.clone());
        self.sysbus.set_scheduler(self.scheduler.clone());
        self.sysbus.set_io_devices(self.io_devs.clone());
        self.sysbus.cartridge.update_from(decoded.cartridge);
        self.sysbus.created();
        self.cycles_to_next_event = 1;

        Ok(())
    }

    pub fn get_game_title(&self) -> String {
        self.sysbus.cartridge.header.game_title.clone()
    }

    pub fn get_game_code(&self) -> String {
        self.sysbus.cartridge.header.game_code.clone()
    }

    #[inline]
    pub fn key_poll(&mut self) {
        self.sysbus.io.keyinput = self.input_device.borrow_mut().poll();
    }

    pub fn frame(&mut self) {
        self.key_poll();

        let mut scheduler = self.scheduler.clone();

        let mut remaining_cycles = CYCLES_FULL_REFRESH - self.overshoot_cycles;

        while remaining_cycles > 0 {
            let cycles = self.step(&mut scheduler);
            if remaining_cycles >= cycles {
                remaining_cycles -= cycles;
            } else {
                self.overshoot_cycles = cycles - remaining_cycles;
                return;
            }
        }

        self.overshoot_cycles = 0;
    }

    pub fn add_breakpoint(&mut self, addr: u32) -> Option<usize> {
        if !self.cpu.breakpoints.contains(&addr) {
            let new_index = self.cpu.breakpoints.len();
            self.cpu.breakpoints.push(addr);
            Some(new_index)
        } else {
            None
        }
    }

    pub fn check_breakpoint(&self) -> Option<u32> {
        let next_pc = self.cpu.get_next_pc();
        for bp in &self.cpu.breakpoints {
            if (*bp & !1) == next_pc {
                return Some(*bp);
            }
        }

        None
    }

    pub fn skip_bios(&mut self) {
        self.cpu.skip_bios();
        self.sysbus.io.gpu.skip_bios();
    }

    pub fn step_cpu(&mut self, io: &mut IoDevices) -> usize {
        if io.intc.irq_pending() {
            self.cpu.irq(&mut self.sysbus);
            io.haltcnt = HaltState::Running;
        }
        let previous_cycles = self.cpu.cycles;
        self.cpu.step(&mut self.sysbus);
        self.cpu.cycles - previous_cycles
    }

    pub fn step(&mut self, scheduler: &mut Scheduler) -> usize {
        // I hate myself for doing this, but rust left me no choice.
        let io = unsafe {
            let ptr = &mut *self.sysbus as *mut SysBus;
            &mut (*ptr).io as &mut IoDevices
        };

        let available_cycles = self.scheduler.get_cycles_to_next_event();
        let mut cycles_left = available_cycles;
        let mut cycles = 0;

        while cycles_left > 0 {
            let _cycles = if !io.dmac.is_active() {
                if HaltState::Running == io.haltcnt {
                    self.step_cpu(io)
                } else {
                    cycles = cycles_left;
                    break;
                }
            } else {
                io.dmac.perform_work(&mut self.sysbus);
                return cycles;
            };

            cycles += _cycles;
            if cycles_left < _cycles {
                break;
            }
            cycles_left -= _cycles;
        }

        io.timers.update(cycles, &mut self.sysbus);

        scheduler.run(cycles, self);

        cycles
    }

    #[cfg(feature = "debugger")]
    /// 'step' function that checks for breakpoints
    /// TODO avoid code duplication
    pub fn step_debugger(&mut self) -> Option<u32> {
        // I hate myself for doing this, but rust left me no choice.
        let io = unsafe {
            let ptr = &mut *self.sysbus as *mut SysBus;
            &mut (*ptr).io as &mut IoDevices
        };

        // clear any pending DMAs
        while io.dmac.is_active() {
            io.dmac.perform_work(&mut self.sysbus);
        }

        let cycles = self.step_cpu(io);
        let breakpoint = self.check_breakpoint();

        io.timers.update(cycles, &mut self.sysbus);

        // update gpu & sound
        let mut scheduler = self.scheduler.clone();
        scheduler.run(cycles, self);

        breakpoint
    }

    /// Query the emulator for the recently drawn framebuffer.
    /// for use with implementations where the VideoInterface is not a viable option.
    pub fn get_frame_buffer(&self) -> &[u32] {
        self.sysbus.io.gpu.get_frame_buffer()
    }

    /// Reset the emulator
    pub fn soft_reset(&mut self) {
        self.cpu.reset(&mut self.sysbus);
    }
}

impl EventHandler for GameBoyAdvance {
    fn handle_event(&mut self, event: EventType, extra_cycles: usize) {
        let io = unsafe {
            let ptr = &mut *self.sysbus as *mut SysBus;
            &mut (*ptr).io as &mut IoDevices
        };
        match event {
            EventType::DmaActivateChannel(channel_id) => io.dmac.activate_channel(channel_id),
            EventType::Gpu(event) => io.gpu.on_event(
                event,
                extra_cycles,
                self.sysbus.as_mut(),
                #[cfg(not(feature = "no_video_interface"))]
                &self.video_device,
            ),
            EventType::Apu(event) => io.sound.on_event(event, extra_cycles, &self.audio_device),
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use std::cell::RefCell;
    use std::rc::Rc;

    use super::super::bus::Bus;
    use super::super::cartridge::GamepakBuilder;

    struct DummyInterface {}

    impl DummyInterface {
        fn new() -> DummyInterface {
            DummyInterface {}
        }
    }

    #[cfg(not(feature = "no_video_interface"))]
    impl VideoInterface for DummyInterface {}
    impl AudioInterface for DummyInterface {}
    impl InputInterface for DummyInterface {}

    fn make_mock_gba(rom: &[u8]) -> GameBoyAdvance {
        let bios = vec![0; 0x4000].into_boxed_slice();
        let cartridge = GamepakBuilder::new()
            .buffer(rom)
            .with_sram()
            .without_backup_to_file()
            .build()
            .unwrap();
        let dummy = Rc::new(RefCell::new(DummyInterface::new()));
        let mut gba = GameBoyAdvance::new(
            bios,
            cartridge,
            #[cfg(not(feature = "no_video_interface"))]
            dummy.clone(),
            dummy.clone(),
            dummy.clone(),
        );
        gba.skip_bios();

        gba
    }

    #[test]
    fn test_arm7tdmi_arm_eggvance() {
        let mut gba = make_mock_gba(include_bytes!("../../external/gba-suite/arm/arm.gba"));

        for _ in 0..10 {
            gba.frame();
        }

        let insn = gba.sysbus.read_32(gba.cpu.pc - 8);
        assert_eq!(insn, 0xeafffffe); // loop
        assert_eq!(0, gba.cpu.gpr[12]);
    }

    #[test]
    fn test_arm7tdmi_thumb_eggvance() {
        let mut gba = make_mock_gba(include_bytes!("../../external/gba-suite/thumb/thumb.gba"));

        for _ in 0..10 {
            gba.frame();
        }

        let insn = gba.sysbus.read_16(gba.cpu.pc - 4);
        assert_eq!(insn, 0xe7fe); // loop
        assert_eq!(0, gba.cpu.gpr[7]);
    }
}