use super::*;
use crate::native_core::apu::ApuStateTail;
use crate::native_core::state_io as sio;

const BUS_STATE_CTX: &str = "bus state";

impl NativeBus {
    pub fn save_state(&self, out: &mut Vec<u8>) {
        out.extend_from_slice(&self.cpu_ram);
        self.ppu.save_state(out);
        out.extend_from_slice(self.apu.registers());
        out.push(self.cpu_open_bus);
        out.push(self.joypad_state);
        out.push(self.joypad_shift);
        out.push(self.joypad2_state);
        out.push(self.joypad2_shift);
        out.push(u8::from(self.joypad_strobe));
        out.push(u8::from(self.nmi_pending));
        out.extend_from_slice(&self.ppu_dot.to_le_bytes());
        out.push(u8::from(self.odd_frame));
        out.push(u8::from(self.in_vblank));
        out.push(u8::from(self.mmc3_a12_prev_high));
        out.extend_from_slice(&self.mmc3_a12_low_dots.to_le_bytes());
        out.extend_from_slice(&self.mmc3_last_irq_scanline.to_le_bytes());
        self.apu.save_state_tail(out);

        let mut mapper_state = Vec::new();
        self.mapper.save_state(&mut mapper_state);
        out.extend_from_slice(&(mapper_state.len() as u32).to_le_bytes());
        out.extend_from_slice(&mapper_state);
    }

    pub fn load_state(&mut self, data: &[u8]) -> Result<(), String> {
        let mut cursor = 0usize;

        self.cpu_ram.copy_from_slice(sio::take_exact(
            data,
            &mut cursor,
            CPU_RAM_SIZE,
            BUS_STATE_CTX,
        )?);
        let ppu_consumed = self.ppu.load_state(&data[cursor..])?;
        cursor = cursor.saturating_add(ppu_consumed);
        let mut apu_regs = [0u8; 0x20];
        apu_regs.copy_from_slice(sio::take_exact(data, &mut cursor, 0x20, BUS_STATE_CTX)?);
        self.apu.set_registers(apu_regs);
        self.frame_complete = false;

        self.cpu_open_bus = sio::take_u8(data, &mut cursor, BUS_STATE_CTX)?;
        self.joypad_state = sio::take_u8(data, &mut cursor, BUS_STATE_CTX)?;
        self.joypad_shift = sio::take_u8(data, &mut cursor, BUS_STATE_CTX)?;
        self.joypad2_state = sio::take_u8(data, &mut cursor, BUS_STATE_CTX)?;
        self.joypad2_shift = sio::take_u8(data, &mut cursor, BUS_STATE_CTX)?;
        self.joypad_strobe = sio::take_u8(data, &mut cursor, BUS_STATE_CTX)? != 0;
        self.nmi_pending = sio::take_u8(data, &mut cursor, BUS_STATE_CTX)? != 0;
        self.suppress_vblank_this_frame = false;
        self.ppu_dot = sio::take_u32(data, &mut cursor, BUS_STATE_CTX)?;
        self.ppu_dot %= PPU_DOTS_PER_FRAME;
        self.odd_frame = sio::take_u8(data, &mut cursor, BUS_STATE_CTX)? != 0;
        self.in_vblank = sio::take_u8(data, &mut cursor, BUS_STATE_CTX)? != 0;
        self.mmc3_a12_prev_high = sio::take_u8(data, &mut cursor, BUS_STATE_CTX)? != 0;
        self.mmc3_a12_low_dots = u16::from_le_bytes([
            sio::take_u8(data, &mut cursor, BUS_STATE_CTX)?,
            sio::take_u8(data, &mut cursor, BUS_STATE_CTX)?,
        ]);
        self.mmc3_last_irq_scanline = u32::from_le_bytes([
            sio::take_u8(data, &mut cursor, BUS_STATE_CTX)?,
            sio::take_u8(data, &mut cursor, BUS_STATE_CTX)?,
            sio::take_u8(data, &mut cursor, BUS_STATE_CTX)?,
            sio::take_u8(data, &mut cursor, BUS_STATE_CTX)?,
        ]);
        let frame_cycle = sio::take_u32(data, &mut cursor, BUS_STATE_CTX)?;
        let frame_mode_5step = sio::take_u8(data, &mut cursor, BUS_STATE_CTX)? != 0;
        let frame_irq_inhibit = sio::take_u8(data, &mut cursor, BUS_STATE_CTX)? != 0;
        let frame_irq_pending = sio::take_u8(data, &mut cursor, BUS_STATE_CTX)? != 0;
        let channel_enable_mask = sio::take_u8(data, &mut cursor, BUS_STATE_CTX)?;
        let mut length_counters = [0u8; 4];
        length_counters.copy_from_slice(sio::take_exact(data, &mut cursor, 4, BUS_STATE_CTX)?);
        let dmc_bytes_remaining = u16::from_le_bytes([
            sio::take_u8(data, &mut cursor, BUS_STATE_CTX)?,
            sio::take_u8(data, &mut cursor, BUS_STATE_CTX)?,
        ]);
        let dmc_irq_enabled = sio::take_u8(data, &mut cursor, BUS_STATE_CTX)? != 0;
        let dmc_irq_pending = sio::take_u8(data, &mut cursor, BUS_STATE_CTX)? != 0;
        let dmc_cycle_counter = u16::from_le_bytes([
            sio::take_u8(data, &mut cursor, BUS_STATE_CTX)?,
            sio::take_u8(data, &mut cursor, BUS_STATE_CTX)?,
        ]);
        let dmc_current_addr = u16::from_le_bytes([
            sio::take_u8(data, &mut cursor, BUS_STATE_CTX)?,
            sio::take_u8(data, &mut cursor, BUS_STATE_CTX)?,
        ]);
        let dmc_sample_buffer = sio::take_u8(data, &mut cursor, BUS_STATE_CTX)?;
        let dmc_sample_buffer_valid = sio::take_u8(data, &mut cursor, BUS_STATE_CTX)? != 0;
        let dmc_shift_reg = sio::take_u8(data, &mut cursor, BUS_STATE_CTX)?;
        let dmc_bits_remaining = sio::take_u8(data, &mut cursor, BUS_STATE_CTX)?;
        let dmc_silence = sio::take_u8(data, &mut cursor, BUS_STATE_CTX)? != 0;
        let dmc_output_level = sio::take_u8(data, &mut cursor, BUS_STATE_CTX)?;
        let dmc_dma_request = sio::take_u8(data, &mut cursor, BUS_STATE_CTX)? != 0;
        let mut envelope_divider = [0u8; 3];
        envelope_divider.copy_from_slice(sio::take_exact(data, &mut cursor, 3, BUS_STATE_CTX)?);
        let mut envelope_decay = [0u8; 3];
        envelope_decay.copy_from_slice(sio::take_exact(data, &mut cursor, 3, BUS_STATE_CTX)?);
        let envelope_start_flags = sio::take_u8(data, &mut cursor, BUS_STATE_CTX)?;
        let triangle_linear_counter = sio::take_u8(data, &mut cursor, BUS_STATE_CTX)?;
        let triangle_linear_reload_flag = sio::take_u8(data, &mut cursor, BUS_STATE_CTX)? != 0;
        let mut sweep_divider = [0u8; 2];
        sweep_divider.copy_from_slice(sio::take_exact(data, &mut cursor, 2, BUS_STATE_CTX)?);
        let sweep_reload_flags = sio::take_u8(data, &mut cursor, BUS_STATE_CTX)?;
        let cpu_cycle_parity = sio::take_u8(data, &mut cursor, BUS_STATE_CTX)? != 0;
        let frame_reset_pending = sio::take_u8(data, &mut cursor, BUS_STATE_CTX)? != 0;
        let frame_reset_delay = sio::take_u8(data, &mut cursor, BUS_STATE_CTX)?;
        let pending_frame_mode_5step = sio::take_u8(data, &mut cursor, BUS_STATE_CTX)? != 0;
        let pending_frame_irq_inhibit = sio::take_u8(data, &mut cursor, BUS_STATE_CTX)? != 0;
        let pulse_timer_counter = [
            u16::from_le_bytes([
                sio::take_u8(data, &mut cursor, BUS_STATE_CTX)?,
                sio::take_u8(data, &mut cursor, BUS_STATE_CTX)?,
            ]),
            u16::from_le_bytes([
                sio::take_u8(data, &mut cursor, BUS_STATE_CTX)?,
                sio::take_u8(data, &mut cursor, BUS_STATE_CTX)?,
            ]),
        ];
        let mut pulse_duty_step = [0u8; 2];
        pulse_duty_step.copy_from_slice(sio::take_exact(data, &mut cursor, 2, BUS_STATE_CTX)?);
        let triangle_timer_counter = u16::from_le_bytes([
            sio::take_u8(data, &mut cursor, BUS_STATE_CTX)?,
            sio::take_u8(data, &mut cursor, BUS_STATE_CTX)?,
        ]);
        let triangle_step = sio::take_u8(data, &mut cursor, BUS_STATE_CTX)?;
        let noise_timer_counter = u16::from_le_bytes([
            sio::take_u8(data, &mut cursor, BUS_STATE_CTX)?,
            sio::take_u8(data, &mut cursor, BUS_STATE_CTX)?,
        ]);
        let noise_lfsr = u16::from_le_bytes([
            sio::take_u8(data, &mut cursor, BUS_STATE_CTX)?,
            sio::take_u8(data, &mut cursor, BUS_STATE_CTX)?,
        ]);
        self.apu.load_state_tail(ApuStateTail {
            frame_cycle,
            frame_mode_5step,
            frame_irq_inhibit,
            frame_irq_pending,
            channel_enable_mask,
            length_counters,
            dmc_bytes_remaining,
            dmc_irq_enabled,
            dmc_irq_pending,
            dmc_cycle_counter,
            dmc_current_addr,
            dmc_sample_buffer,
            dmc_sample_buffer_valid,
            dmc_shift_reg,
            dmc_bits_remaining,
            dmc_silence,
            dmc_output_level,
            dmc_dma_request,
            envelope_divider,
            envelope_decay,
            envelope_start_flags,
            triangle_linear_counter,
            triangle_linear_reload_flag,
            sweep_divider,
            sweep_reload_flags,
            cpu_cycle_parity,
            frame_reset_pending,
            frame_reset_delay,
            pending_frame_mode_5step,
            pending_frame_irq_inhibit,
            pulse_timer_counter,
            pulse_duty_step,
            triangle_timer_counter,
            triangle_step,
            noise_timer_counter,
            noise_lfsr,
        });
        let mapper_len = sio::take_u32(data, &mut cursor, BUS_STATE_CTX)? as usize;
        let mapper_state = sio::take_exact(data, &mut cursor, mapper_len, BUS_STATE_CTX)?;

        self.ppu.set_vblank(self.in_vblank);
        self.mapper.load_state(mapper_state)?;

        if cursor != data.len() {
            return Err("bus state: trailing bytes in payload".to_string());
        }
        Ok(())
    }
}