// utility.c
// Utilities for the SplitBit CPU Emulator
// Written by Anachronaut
// 10/15/2024

#include "utility.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <getopt.h>
#include "../Assembler/assembly.h"

void printHelp(const char *programName) {
    printf("Usage: %s [OPTIONS] [boot image]\n", programName);
    printf("\n");
    printf("Named an image, it is placed into memory and started, which is what a\n");
    printf("debugger does and how the test suite runs. Given only a disk, the machine\n");
    printf("starts the way hardware would: the built in ROM is shadowed into Program\n");
    printf("Memory, and it reads the disk for everything else.\n");
    printf("\n");
    printf("Options:\n");
    printf("  -d, --debug       Enable debug mode.\n");
    printf("  -c, --cycles N    Stop after N cycles instead of running until the program halts.\n");
    printf("  -f, --fast        Run as fast as possible, ignoring the emulated cycle rate.\n");
    printf("  -D, --disk FILE   Attach a disk image, making one if it is not there.\n");
    printf("  -L, --disk-cycles N  How many cycles a block read or write takes. Zero, the\n");
    printf("                       default, finishes before the next instruction starts.\n");
    printf("  -W, --write-protect  Attach the disk read only. A disk the host will not let\n");
    printf("                    you write is read only whether you ask for this or not.\n");
    printf("  -S, --screen FILE Save a picture of the screen, as a PPM, when the machine\n");
    printf("                    stops. Works with or without a window, which is how the\n");
    printf("                    tests look at a screen on a host that has no display.\n");
    printf("  -K, --keyboard FILE  Feed the console from this file as though it were a\n");
    printf("                    keyboard rather than a terminal. Which means the console does\n");
    printf("                    its own line editing, the way it must when a window is open\n");
    printf("                    and there is no terminal behind it to do it.\n");
    printf("  -N, --sound FILE  Save every sample the machine made, as raw signed 16 bit\n");
    printf("                    at 48kHz. What --screen is for a picture: the only way to\n");
    printf("                    check a sound on a machine with no speaker.\n");
    printf("  -h, --help        Display this help message.\n");
}

uint8_t parseOptions(int argc, char *argv[], EmulatorOptions *options) {
    static struct option long_options[] = {
        {"debug",  no_argument,       0, 'd'},
        {"cycles", required_argument, 0, 'c'},
        {"fast",   no_argument,       0, 'f'},
        {"disk",   required_argument, 0, 'D'},
        {"ram-disk", required_argument, 0, 'R'},
        {"write-protect", no_argument, 0, 'W'},
        {"disk-cycles", required_argument, 0, 'L'},
        {"screen", required_argument, 0, 'S'},
        {"keyboard", required_argument, 0, 'K'},
        {"sound", required_argument, 0, 'N'},
        {"help",   no_argument,       0, 'h'},
        {0,        0,                 0,  0 }
        };
        int opt;
        int option_index = 0;

    // ---- Everything off, in one line rather than nine ----
    //
    // This was a list of assignments, one per field, and a list beside a struct drifts from
    // the struct: adding `disks` and `diskCount` left them holding whatever was on the stack,
    // so a machine given one disk was told it already had four drives. The same struct
    // growing a field once before left Voyager linking against an object that disagreed
    // about its size.
    //
    // Every default here is nought or nothing, and a default that is not can be written
    // below this line where it will be read as the exception it is.
    *options = (EmulatorOptions){0};

    // Parse options
    while ((opt = getopt_long(argc, argv, "dc:fhD:WL:S:K:N:R:", long_options, &option_index)) != -1) {
        switch (opt) {
            case 'd':
                options->debug = 1;
            break;
            case 'c': {
                // The count has to be a plain positive number. Anything else is
                // almost certainly a mistyped command line rather than a request
                // to run zero cycles.
                char *end;
                long value = strtol(optarg, &end, 10);
                if (*end != '\0' || value <= 0) {
                    fprintf(stderr, "Error: --cycles needs a positive number, not \"%s\".\n", optarg);
                    return OPTIONS_ERROR;
                }
                options->cycles = (unsigned long)value;
            }
            break;
            case 'f':
                options->fast = 1;
            break;
            case 'D':
                // Each one is the next drive. The first is also left in `disk`, because a
                // machine with one disk is what almost every caller means and reading it
                // that way keeps them all unchanged.
                if (options->diskCount >= DISK_DRIVE_COUNT) {
                    fprintf(stderr, "Error: This machine has %d drives.\n",
                            DISK_DRIVE_COUNT);
                    return 1;
                }
                options->disks[options->diskCount++] = optarg;
                if (options->disk == NULL) {
                    options->disk = optarg;
                }
            break;
            case 'R': {
                char *end;
                const unsigned long blocks = strtoul(optarg, &end, 10);
                if (*optarg == '\0' || *end != '\0' || blocks == 0) {
                    fprintf(stderr, "Error: --ram-disk wants a number of blocks.\n");
                    return 1;
                }
                options->ramDisk = blocks;
            }
            break;
            case 'W':
                options->writeProtect = 1;
            break;
            case 'L':
                options->diskCycles = strtoul(optarg, NULL, 0);
            break;
            case 'S':
                options->screen = optarg;
            break;
            case 'K':
                options->keyboard = optarg;
            break;
            case 'N':
                options->sound = optarg;
            break;
            case 'h':
                printHelp(argv[0]);
                return OPTIONS_HELP;
            default:
                printHelp(argv[0]);
                return OPTIONS_ERROR;
        }
    }
    return OPTIONS_OK;
}

// Writes a byte out as eight binary digits, most significant first. printf's %b is
// a recent addition to C and not available everywhere, so this does it by hand.
// The buffer must have room for nine characters.
static void formatBinary(uint8_t value, char *out) {
    for (int i = 0; i < 8; i++) {
        out[i] = (value & (0x80 >> i)) ? '1' : '0';
    }
    out[8] = '\0';
}

void printRegisters(CPURegisters *cpu, uint8_t *Program, uint8_t *Data) {
    char status[9];
    formatBinary(cpu->Status, status);
    printf("***** CPU Registers *****\n");
    printf("A: 0x%02X\tB: 0x%02X\tQ: 0x%02X\tStatus: 0b%s\n", cpu->A, cpu->B, cpu->Q, status);
    printf("Program Counter: 0x%04X     Current Instruction: 0x%02X (%s)\n", cpu->ProgramCounter, Program[cpu->ProgramCounter],getMnemonic(Program[cpu->ProgramCounter]));
    for (int i = 0; i < DATA_POINTERS; i++) {
        printf(" Data Pointer %d: 0x%04X      Current Data Value: 0x%02X%s\n",
               i, cpu->DataPointer[i], Data[cpu->DataPointer[i]],
               i >= PRESERVED_DATA_POINTERS ? "   (volatile)" : "");
    }
    // The two casts keep these inside Data Memory. The Stack Pointer starts at the
    // very top, so without them the display would read off the end of the array
    // before a single byte has been pushed.
    printf("  Stack Pointer: 0x%04X           Current Value: (0x%02X) (0x%02X)\n", cpu->StackPointer,
           Data[(uint16_t)(cpu->StackPointer + 1)], Data[(uint16_t)(cpu->StackPointer + 2)]);
}