DMA.cpp

//
//  DMA.cpp
//  SDL3Test
//
//  Created by Matt Parsons on 06/03/2026.
//

#include "DMA.hpp"
#include "m68k.h"
#include "Gayle.hpp"

#include "SDL3/SDL.h"

static Gayle* bus;

void CopperAndBlitter(){

    if((bus->chipset->dmacon & 0x280) == 0x280){
        if(bus->chipset->copper.Execute()){return;};
    }

    //do blitter when we have a cycle accurate one
    if((bus->chipset->dmacon & 0x4240) == 0x4240){

       bus->chipset->blitter.Instant();
        return;
    }
}

void CPUAccess(){
    bus->Service();
}



int DMAThread(void* data){

    bus = (Gayle*)data;
    int* colorClock = &bus->chipset->denise.ColorClock;
    int* hLine = &bus->chipset->denise.Hline;
    uint16_t* dmacon = &bus->chipset->dmacon;

    uint64_t cycles = 0;

    auto Bpl1Fetch = [](void){
        int addr = bus->chipset->denise.bpl1pt;
        bus->chipset->denise.bpl1pt += 2;
        bus->chipset->denise.BPL1DAT(true, bus->chipram->Read16(addr));
    };

    auto Bpl2Fetch = [](void){
        int addr = bus->chipset->denise.bpl2pt;
        bus->chipset->denise.bpl2pt += 2;
        bus->chipset->denise.bplxdat[1] = bus->chipram->Read16(addr);
    };

    auto Bpl3Fetch = [](void){
        int addr = bus->chipset->denise.bpl3pt;
        bus->chipset->denise.bpl3pt += 2;
        bus->chipset->denise.bplxdat[2] = bus->chipram->Read16(addr);
    };

    auto Bpl4Fetch = [](void){
        int addr = bus->chipset->denise.bpl4pt;
        bus->chipset->denise.bpl4pt += 2;
        bus->chipset->denise.bplxdat[3] = bus->chipram->Read16(addr);
    };

    auto Bpl5Fetch = [](void){
        int addr = bus->chipset->denise.bpl5pt;
        bus->chipset->denise.bpl5pt += 2;
        bus->chipset->denise.bplxdat[4] = bus->chipram->Read16(addr);
    };

    auto Bpl6Fetch = [](void){
        int addr = bus->chipset->denise.bpl6pt;
        bus->chipset->denise.bpl6pt += 2;
        bus->chipset->denise.bplxdat[5] = bus->chipram->Read16(addr);
    };


    while(1){

        bool fetchActive = false;
        int fetchOffset = 0;

        for(*colorClock = 0; *colorClock < 228; ++(*colorClock)){

            int cc = *colorClock;
            bool slotUsed = false;

            // --- Bitplane DMA (highest priority) ---
            // Read current register state each slot so Copper changes take effect immediately
            bool bplDMAon = (*dmacon & 0x300) == 0x300;
            bool verticalDMA = (*hLine > bus->chipset->denise.vstart && *hLine <= bus->chipset->denise.vstop);
            int dffstrt = bus->chipset->denise.dffstrt;
            int dffstop = bus->chipset->denise.dffstop;

            // Start fetching when we hit dffstrt
            if(!fetchActive && bplDMAon && verticalDMA && cc == dffstrt){
                fetchActive = true;
                fetchOffset = 0;
            }

            if(fetchActive){
                int planes = bus->chipset->denise.planeCount();
                bool hires = bus->chipset->denise.isHires();

                if(hires){
                    // Hires: 8-slot pattern (4-slot repeated twice): BPL4,BPL3,BPL2,BPL1, BPL4,BPL3,BPL2,BPL1
                    int phase = fetchOffset & 7;
                    switch(phase){
                        case 0:
                            if(planes > 3){ Bpl4Fetch(); slotUsed = true; }
                            break;
                        case 1:
                            if(planes > 2){ Bpl3Fetch(); slotUsed = true; }
                            break;
                        case 2:
                            if(planes > 1){ Bpl2Fetch(); slotUsed = true; }
                            break;
                        case 3:
                            if(planes > 0){ Bpl1Fetch(); slotUsed = true; }
                            break;
                        case 4:
                            if(planes > 3){ Bpl4Fetch(); slotUsed = true; }
                            break;
                        case 5:
                            if(planes > 2){ Bpl3Fetch(); slotUsed = true; }
                            break;
                        case 6:
                            if(planes > 1){ Bpl2Fetch(); slotUsed = true; }
                            break;
                        case 7:
                            if(planes > 0){ Bpl1Fetch(); slotUsed = true; }
                            break;
                    }
                    fetchOffset = (fetchOffset + 1) & 7;

                    // Group complete — decide whether to stop or continue
                    if(fetchOffset == 0){
                        if(cc >= dffstop){
                            bus->chipset->denise.applyModulos();
                            fetchActive = false;
                        }
                    }
                }else{
                    // Lowres: 8-slot pattern: free, BPL4, BPL6, BPL2, free, BPL3, BPL5, BPL1
                    int phase = fetchOffset & 7;
                    switch(phase){
                        case 0: // free slot (Copper/Blitter)
                            break;
                        case 1:
                            if(planes > 3){ Bpl4Fetch(); slotUsed = true; }
                            break;
                        case 2:
                            if(planes > 5){ Bpl6Fetch(); slotUsed = true; }
                            break;
                        case 3:
                            if(planes > 1){ Bpl2Fetch(); slotUsed = true; }
                            break;
                        case 4: // free slot (CPU)
                            break;
                        case 5:
                            if(planes > 2){ Bpl3Fetch(); slotUsed = true; }
                            break;
                        case 6:
                            if(planes > 4){ Bpl5Fetch(); slotUsed = true; }
                            break;
                        case 7:
                            if(planes > 0){ Bpl1Fetch(); slotUsed = true; }
                            break;
                    }
                    fetchOffset = (fetchOffset + 1) & 7;

                    // Group complete — decide whether to stop or continue
                    if(fetchOffset == 0){
                        if(cc >= dffstop){
                            bus->chipset->denise.applyModulos();
                            fetchActive = false;
                        }
                    }
                }
            }

            
            // --- Sprite DMA (only if bitplane didn't use this slot) ---
            if(!slotUsed && (*dmacon & 0x220) == 0x220){

                //Sprite 0: slots 21 and 23
                if(cc == 21){
                    if(!bus->chipset->denise.sprite[0].armed){
                        int addr = bus->chipset->denise.sprite[0].pt;
                        bus->chipset->denise.sprite[0].pt += 2;
                        bus->chipset->denise.SPRxPOS(0, true, bus->chipram->Read16(addr));

                        addr = bus->chipset->denise.sprite[0].pt;
                        bus->chipset->denise.sprite[0].pt += 2;
                        bus->chipset->denise.SPRxCTL(0, true, bus->chipram->Read16(addr));
                        slotUsed = true;

                    } else if(*hLine >= bus->chipset->denise.sprite[0].vstart && *hLine <= bus->chipset->denise.sprite[0].vstop){
                        int addr = bus->chipset->denise.sprite[0].pt;
                        bus->chipset->denise.sprite[0].pt += 2;
                        bus->chipset->denise.sprite[0].dat[0] = bus->chipram->Read16(addr);
                        slotUsed = true;
                    }
                }

                if(cc == 23){
                    if(bus->chipset->denise.sprite[0].armed){
                        if(*hLine >= bus->chipset->denise.sprite[0].vstart && *hLine <= bus->chipset->denise.sprite[0].vstop){
                            int addr = bus->chipset->denise.sprite[0].pt;
                            bus->chipset->denise.sprite[0].pt += 2;
                            bus->chipset->denise.SPRxDATB(0, true, bus->chipram->Read16(addr));
                            slotUsed = true;
                        }
                    }
                }
                
                //Sprite 1: slots 25 and 27
                if(cc == 25){
                    if(!bus->chipset->denise.sprite[1].armed){
                        int addr = bus->chipset->denise.sprite[1].pt;
                        bus->chipset->denise.sprite[1].pt += 2;
                        bus->chipset->denise.SPRxPOS(1, true, bus->chipram->Read16(addr));

                        addr = bus->chipset->denise.sprite[1].pt;
                        bus->chipset->denise.sprite[1].pt += 2;
                        bus->chipset->denise.SPRxCTL(1, true, bus->chipram->Read16(addr));
                        slotUsed = true;

                    } else if(*hLine >= bus->chipset->denise.sprite[1].vstart && *hLine <= bus->chipset->denise.sprite[1].vstop){
                        int addr = bus->chipset->denise.sprite[1].pt;
                        bus->chipset->denise.sprite[1].pt += 2;
                        bus->chipset->denise.sprite[1].dat[0] = bus->chipram->Read16(addr);
                        slotUsed = true;
                    }
                }

                if(cc == 27){
                    if(bus->chipset->denise.sprite[1].armed){
                        if(*hLine >= bus->chipset->denise.sprite[1].vstart && *hLine <= bus->chipset->denise.sprite[1].vstop){
                            int addr = bus->chipset->denise.sprite[1].pt;
                            bus->chipset->denise.sprite[1].pt += 2;
                            bus->chipset->denise.SPRxDATB(1, true, bus->chipram->Read16(addr));
                            slotUsed = true;
                        }
                    }
                }
                
                //Sprite 2: slots 29 and 31
                if(cc == 29){
                    if(!bus->chipset->denise.sprite[2].armed){
                        int addr = bus->chipset->denise.sprite[2].pt;
                        bus->chipset->denise.sprite[2].pt += 2;
                        bus->chipset->denise.SPRxPOS(2, true, bus->chipram->Read16(addr));

                        addr = bus->chipset->denise.sprite[2].pt;
                        bus->chipset->denise.sprite[2].pt += 2;
                        bus->chipset->denise.SPRxCTL(2, true, bus->chipram->Read16(addr));
                        slotUsed = true;

                    } else if(*hLine >= bus->chipset->denise.sprite[2].vstart && *hLine <= bus->chipset->denise.sprite[2].vstop){
                        int addr = bus->chipset->denise.sprite[2].pt;
                        bus->chipset->denise.sprite[2].pt += 2;
                        bus->chipset->denise.sprite[2].dat[0] = bus->chipram->Read16(addr);
                        slotUsed = true;
                    }
                }

                if(cc == 31){
                    if(bus->chipset->denise.sprite[2].armed){
                        if(*hLine >= bus->chipset->denise.sprite[2].vstart && *hLine <= bus->chipset->denise.sprite[2].vstop){
                            int addr = bus->chipset->denise.sprite[2].pt;
                            bus->chipset->denise.sprite[2].pt += 2;
                            bus->chipset->denise.SPRxDATB(2, true, bus->chipram->Read16(addr));
                            slotUsed = true;
                        }
                    }
                }

                //Sprite 3: slots 33 and 35
                if(cc == 33){
                    if(!bus->chipset->denise.sprite[3].armed){
                        int addr = bus->chipset->denise.sprite[3].pt;
                        bus->chipset->denise.sprite[3].pt += 2;
                        bus->chipset->denise.SPRxPOS(3, true, bus->chipram->Read16(addr));

                        addr = bus->chipset->denise.sprite[3].pt;
                        bus->chipset->denise.sprite[3].pt += 2;
                        bus->chipset->denise.SPRxCTL(3, true, bus->chipram->Read16(addr));
                        slotUsed = true;

                    } else if(*hLine >= bus->chipset->denise.sprite[3].vstart && *hLine <= bus->chipset->denise.sprite[3].vstop){
                        int addr = bus->chipset->denise.sprite[3].pt;
                        bus->chipset->denise.sprite[3].pt += 2;
                        bus->chipset->denise.sprite[3].dat[0] = bus->chipram->Read16(addr);
                        slotUsed = true;
                    }
                }

                if(cc == 35){
                    if(bus->chipset->denise.sprite[3].armed){
                        if(*hLine >= bus->chipset->denise.sprite[3].vstart && *hLine <= bus->chipset->denise.sprite[3].vstop){
                            int addr = bus->chipset->denise.sprite[3].pt;
                            bus->chipset->denise.sprite[3].pt += 2;
                            bus->chipset->denise.SPRxDATB(3, true, bus->chipram->Read16(addr));
                            slotUsed = true;
                        }
                    }
                }

                //Sprite 4: slots 37 and 39
                if(cc == 37){
                    if(!bus->chipset->denise.sprite[4].armed){
                        int addr = bus->chipset->denise.sprite[4].pt;
                        bus->chipset->denise.sprite[4].pt += 2;
                        bus->chipset->denise.SPRxPOS(4, true, bus->chipram->Read16(addr));

                        addr = bus->chipset->denise.sprite[4].pt;
                        bus->chipset->denise.sprite[4].pt += 2;
                        bus->chipset->denise.SPRxCTL(4, true, bus->chipram->Read16(addr));
                        slotUsed = true;

                    } else if(*hLine >= bus->chipset->denise.sprite[4].vstart && *hLine <= bus->chipset->denise.sprite[4].vstop){
                        int addr = bus->chipset->denise.sprite[4].pt;
                        bus->chipset->denise.sprite[4].pt += 2;
                        bus->chipset->denise.sprite[4].dat[0] = bus->chipram->Read16(addr);
                        slotUsed = true;
                    }
                }

                if(cc == 39){
                    if(bus->chipset->denise.sprite[4].armed){
                        if(*hLine >= bus->chipset->denise.sprite[4].vstart && *hLine <= bus->chipset->denise.sprite[4].vstop){
                            int addr = bus->chipset->denise.sprite[4].pt;
                            bus->chipset->denise.sprite[4].pt += 2;
                            bus->chipset->denise.SPRxDATB(4, true, bus->chipram->Read16(addr));
                            slotUsed = true;
                        }
                    }
                }

                //Sprite 5: slots 41 and 43
                if(cc == 41){
                    if(!bus->chipset->denise.sprite[5].armed){
                        int addr = bus->chipset->denise.sprite[5].pt;
                        bus->chipset->denise.sprite[5].pt += 2;
                        bus->chipset->denise.SPRxPOS(5, true, bus->chipram->Read16(addr));

                        addr = bus->chipset->denise.sprite[5].pt;
                        bus->chipset->denise.sprite[5].pt += 2;
                        bus->chipset->denise.SPRxCTL(5, true, bus->chipram->Read16(addr));
                        slotUsed = true;

                    } else if(*hLine >= bus->chipset->denise.sprite[5].vstart && *hLine <= bus->chipset->denise.sprite[5].vstop){
                        int addr = bus->chipset->denise.sprite[5].pt;
                        bus->chipset->denise.sprite[5].pt += 2;
                        bus->chipset->denise.sprite[5].dat[0] = bus->chipram->Read16(addr);
                        slotUsed = true;
                    }
                }

                if(cc == 43){
                    if(bus->chipset->denise.sprite[5].armed){
                        if(*hLine >= bus->chipset->denise.sprite[5].vstart && *hLine <= bus->chipset->denise.sprite[5].vstop){
                            int addr = bus->chipset->denise.sprite[5].pt;
                            bus->chipset->denise.sprite[5].pt += 2;
                            bus->chipset->denise.SPRxDATB(5, true, bus->chipram->Read16(addr));
                            slotUsed = true;
                        }
                    }
                }

                //Sprite 6: slots 45 and 47
                if(cc == 45){
                    if(!bus->chipset->denise.sprite[6].armed){
                        int addr = bus->chipset->denise.sprite[6].pt;
                        bus->chipset->denise.sprite[6].pt += 2;
                        bus->chipset->denise.SPRxPOS(6, true, bus->chipram->Read16(addr));

                        addr = bus->chipset->denise.sprite[6].pt;
                        bus->chipset->denise.sprite[6].pt += 2;
                        bus->chipset->denise.SPRxCTL(6, true, bus->chipram->Read16(addr));
                        slotUsed = true;

                    } else if(*hLine >= bus->chipset->denise.sprite[6].vstart && *hLine <= bus->chipset->denise.sprite[6].vstop){
                        int addr = bus->chipset->denise.sprite[6].pt;
                        bus->chipset->denise.sprite[6].pt += 2;
                        bus->chipset->denise.sprite[6].dat[0] = bus->chipram->Read16(addr);
                        slotUsed = true;
                    }
                }

                if(cc == 47){
                    if(bus->chipset->denise.sprite[6].armed){
                        if(*hLine >= bus->chipset->denise.sprite[6].vstart && *hLine <= bus->chipset->denise.sprite[6].vstop){
                            int addr = bus->chipset->denise.sprite[6].pt;
                            bus->chipset->denise.sprite[6].pt += 2;
                            bus->chipset->denise.SPRxDATB(6, true, bus->chipram->Read16(addr));
                            slotUsed = true;
                        }
                    }
                }

                //Sprite 7: slots 49 and 51
                if(cc == 49){
                    if(!bus->chipset->denise.sprite[7].armed){
                        int addr = bus->chipset->denise.sprite[7].pt;
                        bus->chipset->denise.sprite[7].pt += 2;
                        bus->chipset->denise.SPRxPOS(7, true, bus->chipram->Read16(addr));

                        addr = bus->chipset->denise.sprite[7].pt;
                        bus->chipset->denise.sprite[7].pt += 2;
                        bus->chipset->denise.SPRxCTL(7, true, bus->chipram->Read16(addr));
                        slotUsed = true;

                    } else if(*hLine >= bus->chipset->denise.sprite[7].vstart && *hLine <= bus->chipset->denise.sprite[7].vstop){
                        int addr = bus->chipset->denise.sprite[7].pt;
                        bus->chipset->denise.sprite[7].pt += 2;
                        bus->chipset->denise.sprite[7].dat[0] = bus->chipram->Read16(addr);
                        slotUsed = true;
                    }
                }

                if(cc == 51){
                    if(bus->chipset->denise.sprite[7].armed){
                        if(*hLine >= bus->chipset->denise.sprite[7].vstart && *hLine <= bus->chipset->denise.sprite[7].vstop){
                            int addr = bus->chipset->denise.sprite[7].pt;
                            bus->chipset->denise.sprite[7].pt += 2;
                            bus->chipset->denise.SPRxDATB(7, true, bus->chipram->Read16(addr));
                            slotUsed = true;
                        }
                    }
                }


            }




            // --- Free slot: Copper (odd) or CPU (even) ---
            if(!slotUsed){
                if(cc & 1){
                    CopperAndBlitter();
                }else{
                    CPUAccess();
                }
            }

            // --- Display output (CC >= 21) ---
            if(cc >= 21){
                bus->chipset->denise.DisplayPixels(bplDMAon);
            }

            // --- CIA ticks ---
            if(cycles % 5 == 0){
                bus->chipset->CIAA.run();
                bus->chipset->CIAB.run();
            }
            cycles++;
        }


        //End of line
        bus->chipset->denise.ResetHLine();
        bus->chipset->CIAB.TOD();

        (*hLine) += 1;
        if(*hLine > 312){
            *hLine = 0;
            bus->chipset->CIAA.TOD();
            bus->chipset->copper.COPJMP1(true, 0);
            bus->chipset->INTREQ(true, 0x8020); //VertB


            // 1. Wait until the main thread gives the green light to process the next frame
            std::unique_lock<std::mutex> lock(bus->chipset->frame_mtx);
            bus->chipset->cv.wait(lock, []{ return bus->chipset->ready_for_next_frame; });

            bus->chipset->ready_for_next_frame = false; // "Lock" the state while we work
            lock.unlock();

        }
    }

}