#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <assert.h>
#include <sysexits.h>

#include <readline/readline.h>

#include "dcpu16.h"

/*
 *  cli driver for dcpu16 core
 *  
 *  Justin Wind <justin.wind@gmail.com>
 *    2012 04 10 - implementation started
 *
 */

static const char * const src_id_ = "$Id$";

/* global invocation options */
struct options {
    unsigned int verbose;
} opt_ = {
    .verbose = 0,
};

#define VERBOSE_PRINTF(...) do { if (opt_.verbose) printf(__VA_ARGS__); } while (0)

static void usage_(char *prog, unsigned int full) {
    FILE *f = full ? stdout : stderr;
    char *x = strrchr(prog, '/');

    if (x && *(x + 1))
        prog = x + 1;

    if (full)
        fprintf(f, "%s -- \n\n",
                prog);

    fprintf(f, "Usage: %s [file]\n",
            prog);

    if (full) {
        fprintf(f, "\nOptions:\n"
                "\t [file] -- ram image to load initially\n"
                "\t -h -- this screen\n"
                "\t -v -- verbose execution tracing\n");

        fprintf(f, "\n%78s\n", src_id_);
    }
}

/* simplified strtoul with range checking */
static
int str_to_word_(char *s) {
    unsigned long l;
    char *ep;

    assert(s);

    errno = 0;
    l = strtoul(s, &ep, 0);

    if (errno
    ||  !(*s && *ep == '\0') ) {
        /* out of range of conversion, or invalid character encountered */
        return -1;
    }

    if (l >= DCPU16_RAM) {
        /* out of range for our needs */
        errno = ERANGE;
        return -1;
    }

    return l;
}

/* clears the instance and loads an image into ram starting at addr */
static
int file_load_(struct dcpu16 *vm, char *filename, DCPU16_WORD addr) {
    FILE *f;
    size_t r;

    assert(addr < DCPU16_RAM);

    dcpu16_reset(vm);

    f = fopen(filename, "rb");
    if (f == NULL) {
        fprintf(stderr, "%s('%s'):%s\n", "fopen", filename, strerror(errno));
        return -1;
    }

    r = fread(vm->ram + addr, sizeof(DCPU16_WORD), DCPU16_RAM - addr, f);
    VERBOSE_PRINTF("read %zu words", r);
    if (addr) VERBOSE_PRINTF(" starting at 0x%04x", addr);
    VERBOSE_PRINTF("\n");

    if (ferror(f))
        fprintf(stderr, "%s('%s'):%s\n", "fread", filename, strerror(errno));

    fclose(f);
    return 0;
}

/* the commands the vm shell can execute */

struct command_ {
    char *name;
    int args_min;
    int args_max;
    int (*func)(struct dcpu16 *, int c, char **v);
    void (*help)(FILE *f, unsigned int);
};

#define COMMAND_IMPL(x) static int command_##x##_(struct dcpu16 *vm, int token_count, char **token_vector)
#define COMMAND_HELP(x) static void command_##x##_help_(FILE *f, unsigned int summary)
#define COMMAND_ENTRY(x, y, z) { #x, y, z, command_##x##_, command_##x##_help_ }


COMMAND_IMPL(quit) {
    (void)vm, (void)token_count, (void)token_vector;
    VERBOSE_PRINTF("done\n");
    return -1;
}
COMMAND_HELP(quit) {
    fprintf(f, "quit\n");
    if (summary) return;

    fprintf(f, "\tExits the emulator.\n");
}


COMMAND_IMPL(load) {
    int addr = 0;

    if (token_count > 1) {
        addr = str_to_word_(token_vector[1]);
        if (addr < 0) {
            fprintf(stderr, "address '%s' is not a valid word: %s\n", token_vector[1], strerror(errno));
            return 0;
        }
    }

    if (file_load_(vm, token_vector[0], addr)) {
        fprintf(stderr, "failed to load '%s'\n", token_vector[0]);
        return 0;
    }
    printf("loaded '%s'", token_vector[0]);
    if (addr) printf(" starting at 0x%04x", addr);
    printf("\n");

    return 0;
}
COMMAND_HELP(load) {
    fprintf(f, "load file [addr]\n");
    if (summary) return;

    fprintf(f, "Usage: load file [addr]\n"
               "\tAttempts to load binary image from 'file' at addr.\n");
}


COMMAND_IMPL(dump) {
    int addr[2];
    int i;

    for (i = 0; i < token_count; i++) {
        addr[i] = str_to_word_(token_vector[i]);
        if (addr[i] < 0) {
            fprintf(stderr, "address '%s' is not a valid word: %s\n", token_vector[i], strerror(errno));
            return 0;
        }
    }
    if (token_count < 1) addr[0] = vm->pc;
    if (token_count < 2) addr[1] = addr[0];

    if (addr[1] < addr[0]) {
        fprintf(stderr, "\t'addr_start' must be before addr_end\n");
        return 0;
    }

    dcpu16_dump_ram(vm, addr[0], addr[1]);

    return 0;
}
COMMAND_HELP(dump) {
    fprintf(f, "dump [addr_start [addr_end]]\n");
    if (summary) return;

    fprintf(f, "\tDisplays contents of ram from addr_start to addr_end.\n");
}


COMMAND_IMPL(disassemble) {
    int addr[2];
    int i;

    for (i = 0; i < token_count; i++) {
        addr[i] = str_to_word_(token_vector[i]);
        if (addr[i] < 0) {
            fprintf(stderr, "address '%s' is not a valid word: %s\n", token_vector[i], strerror(errno));
            return 0;
        }
    }
    if (token_count < 1) addr[0] = vm->pc;
    if (token_count < 2) addr[1] = addr[0];

    if (addr[1] < addr[0]) {
        fprintf(stderr, "\t'addr_start' must be before addr_end\n");
        return 0;
    }

    for (i = addr[0]; i <= addr[1]; i++)
        dcpu16_disassemble_print(vm, i);

    return 0;
}
COMMAND_HELP(disassemble) {
    fprintf(f, "disassemble [addr_start [addr_end]]\n");
    if (summary) return;

    fprintf(f, "\tDisplays contents of ram parsed into instructions.\n");
}


COMMAND_IMPL(step) {
    unsigned long count;
    char *ep;

    (void)token_count;

    errno = 0;
    count = strtoul(token_vector[0], &ep, 0);
    if (errno
    ||  !(*token_vector[0] && *ep == '\0') ) {
        fprintf(stderr, "count '%s' is not a valid number: %s\n", token_vector[0], strerror(errno));
        return 0;
    }

    if (count <= 0) {
        fprintf(stderr, "count must be positive\n");
        return 0;
    }

    while (count--) {
        VERBOSE_PRINTF("executing next cycle, instruction: ");
        dcpu16_disassemble_print(vm, vm->pc), printf("\n");

        dcpu16_step(vm);

        if (opt_.verbose)
            dcpu16_state_print(vm);
    }

    return 0;
}
COMMAND_HELP(step) {
    fprintf(f, "step [count]\n");
    if (summary) return;

    fprintf(f, "\tExecutes the next instruction, or the next count instructions.\n");
}


/* catch sigint while running, stop running */
static volatile unsigned int running_ = 0;
static
void sigint_handler_(int sig) {
    (void)sig;
    running_ = 0;
}
COMMAND_IMPL(run) {
    sig_t osig;
    (void)token_count, (void)token_vector;

    running_ = 1;

    /* install our new interrupt signal handler */
    if ( (osig = signal(SIGINT, sigint_handler_)) ) {
        fprintf(stderr, "%s():%s\n", "signal", strerror(errno));
        return -1;
    }

    while(running_) {
        dcpu16_step(vm);
        if (opt_.verbose)
            dcpu16_state_print(vm);
    }

    /* restore the old interrupt signal handler */
    if (signal(SIGINT, osig) == SIG_ERR) {
        fprintf(stderr, "%s():%s\n", "sigaction", strerror(errno));
        return -1;
    }

    VERBOSE_PRINTF("interrupted...\n");

    return 0;
}
COMMAND_HELP(run) {
    fprintf(f, "run\n");
    if (summary) return;

    fprintf(f, "\tBegins executing continuously.\n");
}

/* gather all these together into a searchable table */
/* help command gets some assistance in declarations */
COMMAND_IMPL(help);
COMMAND_HELP(help);

static struct command_ command_table_[] = {
    COMMAND_ENTRY(help, 0, 1),
    COMMAND_ENTRY(quit, 0, -1),
    COMMAND_ENTRY(load, 1, 2),
    COMMAND_ENTRY(dump, 0, 2),
    COMMAND_ENTRY(disassemble, 0, 2),
    COMMAND_ENTRY(step, 0, 1),
    COMMAND_ENTRY(run, 0, 0),
    { NULL, 0, 0, NULL, NULL }
};

COMMAND_IMPL(help) {
    struct command_ *c;
    (void)vm;

    if (token_count) {
        while (token_count) {
            for (c = command_table_; c->func; c++) {
                if (strcasecmp(*token_vector, c->name) == 0) {
                    if (c->help)
                        c->help(stdout, 0);
                    break;
                }
            }
            token_count--;
            token_vector++;
        }
        return 0;
    }

    for (c = command_table_; c->func; c++) {
        if (c->help)
            c->help(stdout, 1);
    }
    return 0;
}
COMMAND_HELP(help) {
    if (summary) {
        fprintf(f, "help [command]\n");
        return;
    }

    fprintf(f, "Usage: help [command]\n"
               "\tDisplays a list of available commands, or help on a specific command.\n");
}

int main(int argc, char **argv) {
    int c;
    char *line, *line_prev;
    struct dcpu16 *vm;
    char prompt[32];
    const char prompt_fmt[] = "PC:%04x> ";

    while ( (c = getopt(argc, argv, "hv")) != EOF) {
        switch (c) {
            case 'v':
                opt_.verbose++;
                break;

            case 'h':
                usage_(argv[0], 1);
                exit(EX_OK);

            default:
                usage_(argv[0], 0);
                exit(EX_USAGE);
        }
    }
    if (opt_.verbose < 1) {
        dcpu16_warn_cb_set(NULL);
        dcpu16_trace_cb_set(NULL);
    } else if (opt_.verbose < 2) {
        dcpu16_trace_cb_set(NULL);
    }
    argc -= optind;
    argv += optind;

    if ((vm = dcpu16_new()) == NULL) {
        fprintf(stderr, "could not allocate new dcpu instance\n");
        exit(EX_UNAVAILABLE);
    }

    if (argc) {
        file_load_(vm, *argv, 0);
    }

    /* show state, read commands */
    for (line_prev = NULL,
         snprintf(prompt, sizeof prompt, prompt_fmt, vm->pc),
         dcpu16_state_print(vm);

         (line = readline(prompt));

         printf("\n"),
         snprintf(prompt, sizeof prompt, prompt_fmt, vm->pc),
         dcpu16_state_print(vm)) {
        const char whitespace[] = " \t";
        char *rest, *line_start, *command;
        struct command_ *c;
        int token_count;
        char *token_vector[] = { NULL, NULL };
        int r = 0;

        /* skip whitespaces */
        line_start = line + strspn(line, whitespace);

        if (*line_start) {
            /* a new command, it will be the prior command now */
            free(line_prev);
            line_prev = line;
        } else {
            /* empty command, read another line if there's no prior command to repeat */
            if (line_prev == NULL || *line_prev == '\0') {
                continue;
            }

            /* otherwise discard new line and repeat prior */
            free(line);
            line_start = line_prev + strspn(line, whitespace);
            VERBOSE_PRINTF("repeating previous command '%s'\n", line_start);
        }

        /* first word */
        command = strtok_r(line_start, whitespace, &rest);

        /* look up command */
        /* FIXME: tokenize 'rest' into proper argv */
        token_count = 0;
        if (rest)
            token_count++, token_vector[0] = rest;
        for (c = command_table_; c->name; c++) {
            if (strcasecmp(command, c->name) == 0) {
                if (c->args_min > token_count) {
                    fprintf(stderr, "%s: not enough arguments\n", c->name);
                    c->help(stderr, 1);
                    break;
                }

                if (c->args_max > 0
                &&  token_count > c->args_max) {
                    fprintf(stderr, "%s: too many arguments\n", c->name);
                    c->help(stderr, 1);
                    break;
                }

                r = c->func(vm, token_count, token_vector);
                break;
            }
        }
        if (r)
            break;

        if (!c->func)
            fprintf(stderr, "didn't recognize '%s'\n", command);
    }

    printf("\nfinished\n");

    dcpu16_delete(&vm);

    exit(EX_OK);
}