/* disk.c V1.1.1
 *
 * FD17xx emulering for TIKI-100_emul
 * Copyright (C) Asbjørn Djupdal 2000-2001
 */

#include "TIKI-100_emul.h"
#include "protos.h"

#include <string.h>

enum diskCommands {
  NO_COMMAND, READ_SECT, READ_ADDR, WRITE_SECT, READ_TRACK, WRITE_TRACK
};

#define STEPIN     1
#define STEPOUT   -1

/* data for en diskettstasjon */
struct diskParams {
  byte *diskImage;  /* diskettbilde */
  boolean active;   /* om det er diskett i stasjonen */
  int tracks;       /* antall spor */
  int sides;        /* antall sider - 1 */
  int sectors;      /* sektorer pr spor */
  int sectSize;     /* bytes pr sektor */
  int realTrack;    /* hvilken spor r/w-hode står over */
};

/* protos */

static void setLights (void);
static void setLight (int drive, boolean status);

/* variabler */

static struct diskParams params0;   /* data for stasjon 0 */
static struct diskParams params1;   /* data for stasjon 1 */
static struct diskParams *params;   /* data for aktiv plate */

static int side = 0;                /* gjeldende side (0 eller 1) */
static boolean motOn = FALSE;       /* om motor er på */

static byte track = 0;              /* sporregister */
static byte sector = 1;             /* sektorregister */
static byte data = 0;               /* dataregister */
static byte status = 0x20;          /* statusregister */

static byte stepDir = STEPIN;       /* verdi som legges til realTrack ved STEP */
static byte command = NO_COMMAND;   /* kommando som pågår */
static long imageOffset = 0;        /* offset inn i diskImage, ved r/w */
static long endOffset = 0;          /* hvor en r/w kommando skal avslutte */
static int byteCount = 0;           /* antall behandlede bytes ved READ_ADDR, WRITE_TRACK */


/*****************************************************************************/

/* skriv til kontrollregister */
void diskControl (byte value) {
  /* restore */
  if ((value & 0xf0) == 0x00) {
    track = 0;
    params->realTrack = 0;
    status = 0x24;
  }
  /* søk */
  else if ((value & 0xf0) == 0x10) {
    if (data >= params->tracks)
      status = 0x30 | (params->realTrack == 0 ? 0x04 : 0x00);
    else {
      params->realTrack = data;
      track = params->realTrack;
      status = 0x20 | (params->realTrack == 0 ? 0x04 : 0x00);
    }
  }
  /* step */
  else if ((value & 0xe0) == 0x20) {
    params->realTrack += stepDir;
    if (params->realTrack >= params->tracks) params->realTrack = params->tracks - 1;
    if (params->realTrack < 0) params->realTrack = 0;
    status = 0x20 | (params->realTrack == 0 ? 0x04 : 0x00);
    if (value & 0x10)
      track = params->realTrack;
  }
  /* step inn */
  else if ((value & 0xe0) == 0x40) {
    params->realTrack += STEPIN;
    if (params->realTrack >= params->tracks) params->realTrack = params->tracks - 1;
    stepDir = STEPIN;
    status = 0x20;
    if (value & 0x10)
      track = params->realTrack;
  }
  /* step ut */
  else if ((value & 0xe0) == 0x60) {
    params->realTrack += STEPOUT;
    if (params->realTrack < 0) params->realTrack = 0;
    stepDir = STEPOUT;
    status = 0x20 | (params->realTrack == 0 ? 0x04 : 0x00);
    if (value & 0x10)
      track = params->realTrack;
  }
  /* les sektor */
  else if ((value & 0xe0) == 0x80) {
    if (params->active) {
      side = (value & 0x02) ? 1 : 0;
      if ((sector > params->sectors) || (side > params->sides)) {
        status = 0x10;
      }
      else {
        if (value & 0x10) /* les resten av sektor i spor */
          endOffset = (((params->realTrack+1) << params->sides) + side) *      /* BUG ?? */
            params->sectors * params->sectSize;
        else  /* les kun 1 sektor */
          endOffset = ((params->realTrack << params->sides) + side) * params->sectors *
            params->sectSize + sector * params->sectSize;
        imageOffset = ((params->realTrack << params->sides) + side) * params->sectors *
          params->sectSize + (sector-1) * params->sectSize;
        command = READ_SECT;
        status = 0x02;
      }
    } else {
      status = 0x80;
    }
  }
  /* skriv sektor */
  else if ((value & 0xe0) == 0xa0) {
    if (params->active) {
      side = (value & 0x02) ? 1 : 0;
      if ((sector > params->sectors) || (side > params->sides)) {
        status = 0x10;
      }
      else {
        if (value & 0x10) /* skriv resten av sektor i spor */
          endOffset = (((params->realTrack+1) << params->sides) + side) *      /* BUG ?? */
            params->sectors * params->sectSize;
        else  /* skriv kun 1 sektor */
          endOffset = ((params->realTrack << params->sides) + side) * params->sectors *
            params->sectSize + sector * params->sectSize;
        imageOffset = ((params->realTrack << params->sides) + side) * params->sectors *
          params->sectSize + (sector-1) * params->sectSize;
        command = WRITE_SECT;
        status = 0x02;
      }
    } else {
      status = 0x80;
    }
  }
  /* les adresse */
  else if ((value & 0xf8) == 0xc0) {
    if (params->active) {
      side = (value & 0x02) ? 1 : 0;
      if (side > params->sides) {
        status = 0x10;
      }
      else {
        command = READ_ADDR;
        byteCount = 0;
        status = 0x02;
      }
    } else {
      status = 0x80;
    }
  }
  /* les spor -- ikke implementert */
  else if ((value & 0xf8) == 0xe0) {
    status = 0x80;
  }
  /* skriv spor -- kun delvis implementert */
  else if ((value & 0xf8) == 0xf0) {
    if (params->active) {
      side = (value & 0x02) ? 1 : 0;
      if (side > params->sides) {
        status = 0x10;
      }
      else {
        command = WRITE_TRACK;
        byteCount = 0;
        status = 0x02;
      }
    } else {
      status = 0x80;
    }
  }
  /* avbryt */
  else if ((value & 0xf0) == 0xd0) {
    command = NO_COMMAND;
    if (status & 0x01) {
      status = status & 0xfe;
    } else {
      status = 0x20 | (params->realTrack == 0 ? 0x04 : 0x00);
    }
  }
}
/* skriv til sporregister */
void newTrack (byte value) {
  track = value;
}
/* skriv til sektorregister */
void newSector (byte value) {
  sector = value;
}
/* skriv til dataregister */
void newDiskData (byte value) {
  data = value;
  switch (command) {
    case WRITE_SECT:
      params->diskImage[imageOffset++] = data;
      if (imageOffset == endOffset) {
        command = NO_COMMAND;
        status = 0x00;
      }
      break;
    case WRITE_TRACK:
      /* kun delvis implementert */
      if (++byteCount > 6200) {
        memset (&params->diskImage[((params->realTrack << params->sides) + side) * params->sectors *
                                  params->sectSize],
                0xe5, params->sectors * params->sectSize);
        command = NO_COMMAND;
        status = 0x00;
      }
      break;
  }
}
/* les statusregister */
byte diskStatus (void) {
  return status;
}
/* les sporregister */
byte getTrack (void) {
  return track;
}
/* les sektorregister */
byte getSector (void) {
  return sector;
}
/* les dataregister */
byte getDiskData (void) {
  switch (command) {
    case READ_SECT:
      data = params->diskImage[imageOffset++];
      if (imageOffset == endOffset) {
        command = NO_COMMAND;
        status = 0x00;
      }
      break;
    case READ_ADDR:
      switch (byteCount++) {
        case 0: data = params->realTrack; break;
        case 1: data = side; break;
        case 2: data = 1; break;
        case 3: switch (params->sectSize) {
          case 128: data = 0; break;
          case 256: data = 1; break;
          case 512: data = 2; break;
          case 1024: data = 3; break;
        }
        break;
        case 4: data = 0; break;
        case 5: data = 0;
          command = NO_COMMAND;
          status = 0x00;
          break;
      }
      break;
    case READ_TRACK:
      /* ikke implementert */
      break;
  }
  return data;
}
/* sett disk 0 aktiv / inaktiv */
void disk0 (boolean status) {
  if (status) {
    params = &params0;
  } else {
    params = &params1;
  }
  setLights();
}
/* sett disk 1 aktiv / inaktiv */
void disk1 (boolean status) {
  if (status) {
    params = &params1;
  } else {
    params = &params0;
  }
  setLights();
}
/* skru motor på / av */
void diskMotor (boolean status) {
  motOn = status;
  setLights();
}
/* sett alle disklys */
static void setLights (void) {
  int disk = params == &params0 ? 0 : 1;
  int otherDisk = disk == 1 ? 0 : 1;

  if (motOn) {
    setLight (disk, 1);
    setLight (otherDisk, 0);
  } else {
    setLight (0, 0);
    setLight (1, 0);
  }
}
/* sett disk lys til gitt stasjon og status */
static void setLight (int drive, boolean status) {
  static int l[2] = {0, 0};

  if (l[drive] != status) {
    l[drive] = status;
    diskLight (drive, status);
  }
}
/* ny diskett i stasjon
 * disk:      Hvilken stasjon
 * diskImage: Peker til diskettbilde-data
 * resten er diskparametre
 */
void insertDisk (int drive, byte *dskImg, int trcks, int sds,
                 int sctrs, int sctSize) {
  struct diskParams *dp = drive ? &params1 : &params0;

  dp->active = TRUE;
  dp->diskImage = dskImg;
  dp->tracks = trcks;
  dp->sides = sds - 1;
  dp->sectors = sctrs;
  dp->sectSize = sctSize;
}
/* fjern diskett fra stasjon */
void removeDisk (int drive) {
  struct diskParams *dp = drive ? &params1 :&params0;

  dp->active = FALSE;
}