use super::{
    NativeBus, PPU_DOTS_PER_FRAME, PPU_DOTS_PER_SCANLINE, PPU_PRERENDER_SCANLINE,
    PPU_VBLANK_START_SCANLINE,
};
use crate::native_core::cpu::CpuBus;
use crate::native_core::mapper::Mapper;

impl NativeBus {
    fn clock_one_cpu_cycle(&mut self) {
        self.cpu_cycles_since_poll = self.cpu_cycles_since_poll.saturating_add(1);
        for _ in 0..3 {
            self.clock_ppu_dot();
        }
        self.mapper.clock_cpu(1);
        self.apu.clock_cpu_cycle();
    }

    fn service_dmc_dma(&mut self, addr: u16) {
        let byte = self.dma_read(addr);
        self.apu.provide_dmc_dma_byte(byte);
        // DMC DMA steals CPU bus cycles while APU/PPU/mapper keep ticking.
        for _ in 0..4 {
            self.clock_one_cpu_cycle();
        }
    }

    pub(super) fn dma_read(&mut self, addr: u16) -> u8 {
        <Self as CpuBus>::read(self, addr)
    }

    pub(super) fn clock_ppu_dot(&mut self) {
        self.ppu_dot += 1;
        if self.ppu_dot >= PPU_DOTS_PER_FRAME {
            self.ppu_dot = 0;
            self.frame_complete = true;
            self.odd_frame = !self.odd_frame;
        }

        let scanline = self.ppu_dot / PPU_DOTS_PER_SCANLINE;
        let dot = self.ppu_dot % PPU_DOTS_PER_SCANLINE;
        let rendering_enabled = self.ppu.rendering_enabled();

        {
            let mapper: &(dyn Mapper + Send) = &*self.mapper;
            self.ppu.render_dot(mapper, scanline, dot);
        }

        if rendering_enabled && (scanline < 240 || scanline == PPU_PRERENDER_SCANLINE) {
            if self.mapper.needs_ppu_a12_clock() {
                let a12_high = self.ppu.mmc3_a12_high_at(scanline, dot);
                if a12_high {
                    if !self.mmc3_a12_prev_high
                        && self.mmc3_a12_low_dots >= 8
                        && self.mmc3_last_irq_scanline != scanline
                    {
                        self.mapper.clock_scanline();
                        self.mmc3_last_irq_scanline = scanline;
                    }
                    self.mmc3_a12_prev_high = true;
                    self.mmc3_a12_low_dots = 0;
                } else {
                    self.mmc3_a12_prev_high = false;
                    self.mmc3_a12_low_dots = self.mmc3_a12_low_dots.saturating_add(1);
                }
            } else if dot == 260 {
                self.mapper.clock_scanline();
            }
        } else {
            self.mmc3_a12_prev_high = false;
            self.mmc3_a12_low_dots = self.mmc3_a12_low_dots.saturating_add(1);
        }
        if rendering_enabled && scanline == PPU_PRERENDER_SCANLINE && dot == 339 && self.odd_frame {
            // NTSC odd frame timing: skip pre-render dot 340 when rendering is enabled.
            self.ppu_dot = self.ppu_dot.saturating_add(1);
        }

        if !self.in_vblank && scanline == PPU_VBLANK_START_SCANLINE && dot == 1 {
            if self.suppress_vblank_this_frame {
                self.suppress_vblank_this_frame = false;
                self.in_vblank = false;
                self.ppu.set_vblank(false);
            } else {
                self.in_vblank = true;
                self.ppu.set_vblank(true);
                if self.ppu.nmi_enabled() {
                    self.nmi_pending = true;
                }
            }
        } else if scanline == PPU_PRERENDER_SCANLINE && dot == 1 {
            self.in_vblank = false;
            self.ppu.set_vblank(false);
            self.ppu.set_sprite0_hit(false);
            self.ppu.set_sprite_overflow(false);
            self.suppress_vblank_this_frame = false;
        }
    }

    pub(super) fn clock_cpu_cycles(&mut self, cycles: u32) {
        if cycles == 0 {
            return;
        }
        let mut remaining = cycles;
        while remaining != 0 {
            self.clock_one_cpu_cycle();
            while let Some(addr) = self.apu.take_dmc_dma_request() {
                self.service_dmc_dma(addr);
            }
            remaining -= 1;
        }
    }

    pub(super) fn note_scroll_write_now(&mut self) {
        let scanline = (self.ppu_dot / PPU_DOTS_PER_SCANLINE) as usize;
        let dot = self.ppu_dot % PPU_DOTS_PER_SCANLINE;
        self.ppu.note_scroll_register_write(scanline, dot);
    }
}