//
//  woz.c
//  A2Mac
//
//  Created by Tamas Rudnai on 2/15/20.
//  Copyright © 2020 GameAlloy. All rights reserved.
//

#include <stdlib.h>
#include <string.h>

#include "woz.h"
#include "disk.h"
#include "6502.h"
#include "common.h"


WOZread_t WOZread = {0};
uint8_t   WOZlatch = 0;

int trackOffset = 0;
int bitOffset = 0;
uint64_t clkelpased;


woz_header_t woz_header;
woz_chunk_header_t woz_chunk_header;
woz_tmap_t woz_tmap;
woz_trks_t woz_trks;
int track_loaded = -1;



#pragma pack(push, 1)

typedef union trackEntry_u {
    struct {
        uint8_t data;
        uint8_t shift;
    };
    uint16_t shift16;
} trackEntry_t;

#pragma pack(pop)

trackEntry_t prepared_track[WOZ_TRACK_BYTE_COUNT];

typedef enum readState_e {
    readNormal = 0,
    readHold,
} readState_t;

readState_t readState = readNormal;
uint8_t readLatch;


void woz_loadTrack_old( int track ) {
    trackEntry_t reg = {0};

    reg.shift = woz_trks[track].data[0];
    reg.data =  woz_trks[track].data[1];
    prepared_track[0] = reg;

    for ( int offs = 1; offs < WOZ_TRACK_BYTE_COUNT; offs++ ) {
        
        for ( int i = 0; i < 8; i++ ) {
            if (reg.shift & 0x80) {
                reg.shift = 0;
            }
            
            reg.shift16 <<= 1;
        }
        
        reg.data = woz_trks[track].data[ (offs + 1) % WOZ_TRACK_BYTE_COUNT ];
        prepared_track[offs] = reg;
    }
}


typedef enum wozTrackState_e {
    wozTrackState_Start = 0,
    wozTrackState_D5,
    wozTrackState_D5_AA,
    wozTrackState_D5_AA_96,
    wozTrackState_vol1,
    wozTrackState_vol2,
    wozTrackState_trk1,
    wozTrackState_trk2,
    wozTrackState_sec1,
    wozTrackState_sec2,
} wozTrackState_t;


void woz_loadTrack( int track ) {
    trackEntry_t reg = {0};
    wozTrackState_t wozTrackState  = wozTrackState_Start;

    reg.shift = 0;
    reg.data  = 0;
    prepared_track[0] = reg;
    
    int vol = 0;
    int trk = 0;
    int sec = 0;

    int bitOffs_D5_SecHdr = 0; // bit offset of D5 Sector Header
    
    int bitOffs = 0;
    
    for ( int byteOffs = 0; byteOffs < WOZ_TRACK_BYTE_COUNT; byteOffs++ ) {

        reg.data = woz_trks[track].data[ byteOffs ];

        for ( int i = 0; i < 8; i++ ) {
            reg.shift16 <<= 1;
            
            if (reg.shift & 0x80) {
                switch (wozTrackState) {
                    case wozTrackState_D5:
                        switch (reg.shift) {
                            case 0xAA:
//                                printf("D5 AA at bitOffset:%d\n", bitOffs);
                                wozTrackState = wozTrackState_D5_AA;
                                break;
                                
                            default:
                                wozTrackState = wozTrackState_Start;
                                break;
                        }
                        
                        break;
                        
                    case wozTrackState_D5_AA:
                        switch (reg.shift) {
                            case 0x96:
                                wozTrackState = wozTrackState_vol1;
//                                printf("D5 AA 96 at bitOffset:%d\n", bitOffs);
//                                printf("Sector Header at bitOffset:%d\n", bitOffs_D5_SecHdr);
                                break;
                                
                            default:
                                wozTrackState = wozTrackState_Start;
                                break;
                        }
                        
                        break;
                        
                    case wozTrackState_vol1:
                        vol = (reg.shift << 1) | 1;
                        wozTrackState = wozTrackState_vol2;
                        break;
                        
                    case wozTrackState_vol2:
                        vol &= reg.shift;
                        wozTrackState = wozTrackState_trk1;
                        break;
                        
                    case wozTrackState_trk1:
                        trk = (reg.shift << 1) | 1;
                        wozTrackState = wozTrackState_trk2;
                        break;
                        
                    case wozTrackState_trk2:
                        trk &= reg.shift;
                        wozTrackState = wozTrackState_sec1;
                        break;
                        
                    case wozTrackState_sec1:
                        sec = (reg.shift << 1) | 1;
                        wozTrackState = wozTrackState_sec2;
                        break;
                        
                    case wozTrackState_sec2:
                        sec &= reg.shift;
                        wozTrackState = wozTrackState_Start;
                        
                        printf("Vol:%d Track:%d Sector:%d at bitOffset:%d\n", vol, trk, sec, bitOffs_D5_SecHdr);

                        break;
                        
                    default:
                        if ( reg.shift == 0xD5 ) {
//                            printf("D5 at bitOffset:%d\n", bitOffs);
                            wozTrackState = wozTrackState_D5;
                            bitOffs_D5_SecHdr = bitOffs;
                        }
                        break;
                }
                
                reg.shift = 0;
            }
            
            bitOffs++;
        }
    }
}


uint8_t woz_read() {

    int track = woz_tmap.phase[disk.phase.count];
    if (outdev) fprintf(outdev, "track: %d (%d) ", track, disk.phase.count);
    if ( track >= 40 ) {
        dbgPrintf("TRCK TOO HIGH!\n");
        return rand();
    }
    
#ifdef WOZ_REAL_SPIN
    if ( track != track_loaded ) {
        woz_loadTrack(track);
        track_loaded = track;
    }

    WOZread.shift32 = 0;
    bitOffset = (m6502.clktime >> 2) & 7;
    trackOffset = (m6502.clktime >> 5) % WOZ_TRACK_BYTE_COUNT;
    WOZread.next = woz_trks[track].data[ (trackOffset +1) % WOZ_TRACK_BYTE_COUNT ];
    WOZread.data = woz_trks[track].data[ trackOffset ];
    WOZread.prev = woz_trks[track].data[ (trackOffset -1) % WOZ_TRACK_BYTE_COUNT ];
    WOZread.shift = woz_trks[track].data[ (trackOffset -2) % WOZ_TRACK_BYTE_COUNT ];

    printf("clk:%llu  bo:%u  to:%u  W:%08X\n", m6502.clktime, bitOffset, trackOffset, WOZread.shift32);
    
    uint8_t state = 0;
    // simulating the continous shift register in Disk ][
    for (int i = bitOffset + 16; i; --i) {
        
        WOZread.shift32 <<= 1;
        
        switch (state) {
            case 0:
                WOZlatch = WOZread.shift;
                if ( WOZread.valid ) {
                    state = 1;
                    WOZread.shift = 0;
                }
                break;
                
            case 1:
                // we do not latch the shift register for one 4us cycle
                state = 0;
                break;
                
            default:
                // this should not happen
                state = 0;
                break;
        }
        
//                printf("shft1: W:%08X  L:%02X\n", WOZread.shift32, WOZlatch);

    }

    printf("clk:%llu  bo:%u  to:%u  W:%08X  B:%02X\n", m6502.clktime, bitOffset, trackOffset, WOZread.shift32, WOZlatch);
    if ( WOZlatch & 0x80 ) {
        printf("WOZlatch: %02X\n", WOZlatch);
        
        static int readState = 0;
        static int vol = 0;
        static int trk = 0;
        static int sec = 0;
        
        switch (readState) {
            case 0:
                if ( 0xD5 == WOZlatch ) readState = 1;
                else readState = 0;
                break;
                
            case 1:
                if ( 0xAA == WOZlatch ) readState = 2;
                else readState = 0;
                break;
                
            case 2:
                if ( 0x96 == WOZlatch ) {
                    readState = 3;
                    printf("sector header marker\n");
                }
                else if ( 0xAD == WOZlatch ) {
                    readState = 10;
                    printf("sector data marker\n");
                }
                else readState = 0;
                break;
                
            case 3: // sector header, vol number 1
                readState++;
                vol = (WOZlatch << 1) | 1;
                break;
                
            case 4: // sector header, vol number 2
                readState++;
                vol &= WOZlatch;
                printf("vol:%u ", vol);
                break;
                
            case 5: // sector header, trk number 1
                readState++;
                trk = (WOZlatch << 1) | 1;
                break;
                
            case 6: // sector header, trk number 2
                readState++;
                trk &= WOZlatch;
                printf("trk:%u ", trk);
                break;
                
            case 7: // sector header, sec number 1
                readState++;
                sec = (WOZlatch << 1) | 1;
                break;
                
            case 8: // sector header, sec number 2
                readState = 0;
                sec &= WOZlatch;
                printf("sec:%u\n", sec);
                break;
                    

            default:
                readState = 0;
                break;
        }
    }
    
//            switch ( WOZlatch ) {
//                case 0xAA:
//                case 0x96:
////                    printf("%02X ", WOZlatch);
//                    printf("clk:%llu  bo:%u  to:%u  B:%02X\n", m6502.clktime, bitOffset, trackOffset, WOZlatch);
//                    break;
//
//                default:
//                    break;
//            }

    return WOZlatch;

    
#elif defined( WOZ_REAL_SPIN2 )
//    clkelpased = m6502.clktime - disk.clk_last_read;
//    disk.clk_last_read = m6502.clktime;

    bitOffset = (m6502.clktime >> 2) & 7;
    trackOffset = (m6502.clktime >> 5) % WOZ_TRACK_BYTE_COUNT;
    trackEntry_t reg = prepared_track[trackOffset];
    
    do {
        switch (readState) {
            case readNormal:
                readLatch = reg.shift;
                break;
                
            case readHold:
            default:
                readState = readNormal;
                break;
        }

        if (reg.shift & 0x80) {
            reg.shift = 0;
            readState = readHold;
        }
        
        reg.shift16 <<= 1;
    } while ( --bitOffset > 0 );

    printf("READ: clk:%llu  to:%u  bo:%llu  B:%02X\n", m6502.clktime, trackOffset, (m6502.clktime >> 2) & 7, readLatch);
    return readLatch;


#elif defined( WOZ_SEARCH_NEXTSECT )
    
    static int clkBeforeSync = 0;
    
    clkelpased = m6502.clktime + clkfrm - m6502.clklast;
    m6502.clklast = m6502.clktime + clkfrm;
    
    clkBeforeSync += clkelpased;
    
    const int clkBeforeAdjusting = 1024;
    const int magicShiftOffset = 8192;
    
    uint16_t usedBytes = woz_trks[track].bytes_used < WOZ_TRACK_BYTE_COUNT ? woz_trks[track].bytes_used : WOZ_TRACK_BYTE_COUNT;
    
    if ( usedBytes ) {
//        printf("elpased : %llu (clkBefRd:%d)\n", clkelpased, clkBeforeSync);
        if ( clkelpased > clkBeforeAdjusting ) {
//            printf("NEED SYNC : %llu (clkBefRd:%d)\n", clkelpased, clkBeforeSync);
            clkBeforeSync = 0;
//            bitOffset = (clkelpased >> 2) & 7;
//            bitOffset = 0;
//            trackOffset += clkelpased >> 5;
//            trackOffset %= usedBytes;

// preroll data stream
//            WOZread.shift16 = 0;
//            WOZread.data = woz_trks[track].data[trackOffset++];
//            trackOffset %= usedBytes;

//            WOZread.shift16 <<= bitOffset;
            
            int w = 2; // 2 x 0xD5
            
            for ( int i = 0; i < usedBytes * 8; i++ ) {
                if ( ++bitOffset >= 8 ) {
                    bitOffset = 0;
                    
                    trackOffset++;
                    trackOffset %= usedBytes;
                    
                    WOZread.data = woz_trks[track].data[trackOffset];
                }
                
                WOZread.shift16 <<= 1;
                if ( WOZread.valid ) {
                    uint8_t byte = WOZread.shift;
                    WOZread.shift = 0;
                    
                    // find next sector or end of sector
                    if ( byte == 0xD5 ) {
                        // actually 2 sectors, because of DOS 3.3 interleaving algoritm
                        if ( --w <= 0 ) {
                            return byte;
                        }
                    }
                }
            }
            
        }
        
        // to avoid infinite loop and to search for bit 7 high
        for ( int i = 0; i < usedBytes * 8; i++ ) {
            if ( ++bitOffset >= 8 ) {
                bitOffset = 0;
//                    if ( ++trackOffset >= WOZ_TRACK_BYTE_COUNT ) {
//                        trackOffset = 0;
//                    }
                trackOffset++;
                trackOffset %= usedBytes;
                
//                    printf("offs:%u\n", trackOffset);
                WOZread.data = woz_trks[track].data[trackOffset];
            }
            
            WOZread.shift16 <<= 1;
            if ( WOZread.valid ) {
                uint8_t byte = WOZread.shift;
//                    printf("%02X ", byte);
                WOZread.shift = 0;
                if (outdev) fprintf(outdev, "byte: %02X\n", byte);
                
                return byte;
            }
        }
        if (outdev) fprintf(outdev, "TIME OUT!\n");
    }
    
    return rand();
    
#else // WOZ_REAL_SPIN
    static int clkBeforeSync = 0;
    
    clkelpased = m6502.clktime + clkfrm - m6502.clklast;
    m6502.clklast = m6502.clktime + clkfrm;
    
    clkBeforeSync += clkelpased;
    
    const int clkBeforeAdjusting = 512;
    const int magicShiftOffset = 50;
    
    uint16_t usedBytes = woz_trks[track].bytes_used < WOZ_TRACK_BYTE_COUNT ? woz_trks[track].bytes_used : WOZ_TRACK_BYTE_COUNT;
    
    if ( usedBytes ) {
//        printf("elpased : %llu (clkBefRd:%d)\n", clkelpased, clkBeforeSync);
        
        if ( clkelpased > clkBeforeAdjusting ) {
//            printf("NEED SYNC : %llu (clkBefRd:%d)\n", clkelpased, clkBeforeSync);
            clkBeforeSync = 0;
            bitOffset = (clkelpased >> 2) & 7;
            trackOffset += clkelpased >> 5;
            trackOffset %= usedBytes;

            // preroll data stream
            WOZread.shift16 = 0;
            WOZread.data = woz_trks[track].data[trackOffset++];
            trackOffset %= usedBytes;

            WOZread.shift16 <<= bitOffset;

            for ( int i = 0; i < magicShiftOffset; i++ ) {
                for ( ; bitOffset < 8; bitOffset++ ) {
                    WOZread.shift16 <<= 1;

                    if ( WOZread.valid ) {
                        WOZread.shift = 0;
                    }
                }
                WOZread.data = woz_trks[track].data[trackOffset++];
                trackOffset %= usedBytes;
                bitOffset = 0;
            }
        }
        else {
            uint64_t bitForward = (clkelpased >> 2);

            // to avoid infinite loop and to search for bit 7 high
            for ( uint64_t i = 0; i < bitForward; i++ ) {
                if ( ++bitOffset >= 8 ) {
                    bitOffset = 0;
                    trackOffset++;
                    trackOffset %= usedBytes;

                    WOZread.data = woz_trks[track].data[trackOffset];
                }

                WOZread.shift16 <<= 1;

                if ( WOZread.valid ) {
                    WOZread.shift = 0;
                }
            }
        }

        // to avoid infinite loop and to search for bit 7 high
        for ( int i = 0; i < usedBytes * 8; i++ ) {
            if ( WOZread.valid ) {
                uint8_t byte = WOZread.shift;
                WOZread.shift = 0;
//                if (outdev) fprintf(outdev, "byte: %02X\n", byte);
                
                return byte;
            }
            
            if ( ++bitOffset >= 8 ) {
                bitOffset = 0;
                trackOffset++;
                trackOffset %= usedBytes;

                WOZread.data = woz_trks[track].data[trackOffset];
            }
            
            WOZread.shift16 <<= 1;
        }
//        if (outdev) fprintf(outdev, "TIME OUT!\n");
    }
    
    return rand();

#endif // WOZ_REAL_SPIN

}


int woz_loadFile( const char * filename ) {
    
//    char fullpath[256];
//
//    strcpy(fullpath, resourcePath);
//    strcat(fullpath, "/");
//    strcat(fullpath, filename);
    
    FILE * f = fopen(filename, "rb");
    if (f == NULL) {
        perror("Failed to read WOZ: ");
        return WOZ_ERR_FILE_NOT_FOUND;
    }
    
    fread( &woz_header, 1, sizeof(woz_header_t), f);
    if ( woz_header.magic != WOZ1_MAGIC ) {
        return WOZ_ERR_NOT_WOZ_FILE;
    }
    
    while ( ! feof(f) ) {
        // beginning of the chunk, so we can skip it later
        
        long r = fread( &woz_chunk_header, 1, sizeof(woz_chunk_header_t), f);
        if ( r != sizeof(woz_chunk_header_t) ) {
            if ( r ) {
                return WOZ_ERR_BAD_CHUNK_HDR;
            }
            // ok we just reached the end of the file, we should exit properly, close file handle etc
            break;
        }
        long foffs = ftell(f);
        
        void * buf = NULL;

        switch ( woz_chunk_header.magic ) {
            case WOZ_INFO_CHUNK_ID:
                break;

            case WOZ_TMAP_CHUNK_ID:
                buf = &woz_tmap;
                break;

            case WOZ_TRKS_CHUNK_ID:
                buf = woz_trks;
                break;

            case WOZ_META_CHUNK_ID:
                break;

            default:
                break;
        }
        
        if (buf) {
            r = fread( buf, 1, woz_chunk_header.size, f);
            if ( r != woz_chunk_header.size ) {
                return WOZ_ERR_BAD_DATA;
            }
        }

        // make sure we are skipping unhandled chunks correctly
        fseek(f, foffs + woz_chunk_header.size, SEEK_SET);
    }
    
    fclose(f);
    
    
    // DO NOT COMMIT THIS! ONLY FOR DEBUG!!!
//    woz_loadTrack(0x11);

    return WOZ_ERR_OK;
}