#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdarg.h>
#include <inttypes.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/stat.h>
#include <endian.h>
#include <errno.h>

#define ZX_DUMP_STRIDE_LINE 16
#define ZX_DUMP_STRIDE_GROUP 2
#define ZX_DUMP_CHARSET_LEN 64

#define ZX_DUMP_FLAGS_NONE   0
#define ZX_DUMP_FLAGS_BASIC (1 << 0)

#define ZX_CHAR_LOW(c) \
    (c <= ZX_DUMP_CHARSET_LEN)

#define ZX_CHAR_INVERSE_START 0x80
#define ZX_CHAR_INVERSE_END   0xbf

#define ZX_CHAR_INVERSE(c) \
    (c >= ZX_CHAR_INVERSE_START && c <= ZX_CHAR_INVERSE_END)

#define ZX_CHAR_TOKEN_LOW_START 0x40
#define ZX_CHAR_TOKEN_LOW_END   0x42

#define ZX_CHAR_TOKEN_LOW(c) \
    (c >= ZX_CHAR_TOKEN_LOW_START && c <= ZX_CHAR_TOKEN_LOW_END)

#define ZX_CHAR_NEWLINE(c) \
    (c == 0x76)

#define ZX_CHAR_TOKEN_HIGH_START 0xc0
#define ZX_CHAR_TOKEN_HIGH_END   0xff

#define ZX_CHAR_TOKEN_HIGH(c) \
    (c >= 0xc0)

#define ZX_BASIC_STATE_LEN 116

#define ZX_CHAR_TOKEN_INTEGRAL(c) \
    (c == 0x0e)

#define ZX_CHAR_TOKEN_FLOAT(c) \
    (c == 0x7e)

typedef struct _zx_basic_line {
    uint16_t num, len;
} zx_basic_line;

static uint32_t zx_charset[ZX_DUMP_CHARSET_LEN] = {
    0x0020, 0x2598, 0x259d, 0x2580, 0x2596, 0x258c, 0x259e, 0x259b,
    0x2592, '.',    '.',    '"',    0x00a3, '$',    ':',    '?',
    '(',    ')',    '>',    '<',    '=',    '+',    '-',    '*',
    '/',    ';',    ',',    '.',    '0',    '1',    '2',    '3',
    '4',    '5',    '6',    '7',    '8',    '9',    'A',    'B',
    'C',    'D',    'E',    'F',    'G',    'H',    'I',    'J',
    'K',    'L',    'M',    'N',    'O',    'P',    'Q',    'R',
    'S',    'T',    'U',    'V',    'W',    'X',    'Y',    'Z',
};

static char *zx_tokens_low[3] = {
    "RND", "INKEY$", "PI",
};

static char *zx_tokens[64] = {
    "\"\"", "AT",     "TAB",   NULL,   "CODE",   "VAL",   "LEN",   "SIN",
    "COS",  "TAN",    "ASN",   "ACS",  "ATN",    "LN",    "EXP",   "INT",
    "SQR",  "SGN",    "ABS",   "PEEK", "USR",    "STR$",  "CHR$",  "NOT",
    "**",   "OR",     "AND",   "<=",   ">=",     "<>",    "THEN",  "TO",
    "STEP", "LPRINT", "LLIST", "STOP", "SLOW",   "FAST",  "NEW",   "SCROLL",
    "CONT", "DIM",    "REM",   "FOR",  "GOTO",   "GOSUB", "INPUT", "LOAD",
    "LIST", "LET",    "PAUSE", "NEXT", "POKE",   "PRINT", "PLOT",  "RUN",
    "SAVE", "RAND",   "IF",    "CLS",  "UNPLOT", "CLEAR", "RETURN" "COPY",
};

static inline size_t utf8_encode(uint8_t *buf, uint32_t codepoint) {
    if ((codepoint & 0x007f) == codepoint) {
        buf[0] = codepoint & 0x007f;

        return 1;
    } else if ((codepoint & 0x07ff) == codepoint) {
        buf[0] = 0xc0 | ((codepoint & 0x07c0) >> 6);
        buf[1] = 0x80 |  (codepoint & 0x003f);

        return 2;
    } else if ((codepoint & 0xffff) == codepoint) {
        buf[0] = 0xe0 | ((codepoint & 0xf000) >> 12);
        buf[1] = 0x80 | ((codepoint & 0x0fc0) >>  6);
        buf[2] = 0x80 |  (codepoint & 0x003f);

        return 3;
    } else {
        buf[0] = 0xf0 | ((codepoint & 0x1c0000) >> 18);
        buf[1] = 0x80 | ((codepoint & 0x03f000) >> 12);
        buf[2] = 0x80 | ((codepoint & 0x000fc0) >>  6);
        buf[3] = 0x80 |  (codepoint & 0x00003f);

        return 4;
    }
}

static inline int zx_putchar(uint8_t c, int inverse) {
    uint8_t sequence[4];
    size_t len = utf8_encode(sequence, zx_charset[c]);

    if (inverse) {
        if (fputs("\033[7m", stdout) < 0) {
            goto error_io;
        }
    }

    if (fwrite(sequence, len, 1, stdout) < 1) {
        goto error_io;
    }

    if (inverse) {
        if (fputs("\033[27m", stdout) < 0) {
            goto error_io;
        }
    }

    return 0;

error_io:
    return -1;
}

static ssize_t hexdump_line(off_t offset, void *buf, size_t len, int tty) {
    size_t i;

    if (printf("%08zx: ", offset) < 0) {
        goto error_io;
    }

    for (i=0; i<len; i++) {
        if (i > 0 && (i % ZX_DUMP_STRIDE_GROUP) == 0) {
            if (putchar(' ') < 0) {
                goto error_io;
            }
        }

        if (printf("%02x", ((uint8_t *)buf)[offset+i]) < 0) {
            goto error_io;
        }
    }

    if (fputs("  ", stdout) < 0) {
        goto error_io;
    }

    for (i=0; i<len; i++) {
        uint8_t c = ((uint8_t *)buf)[offset+i];

        if (c <= 0x3f) {
            if (zx_putchar(c, 0) < 0) {
                goto error_io;
            }
        } else if (c >= 0xa0 && c <= 0xbf) {
            if (zx_putchar(c - 0xa0, tty) < 0) {
                goto error_io;
            }
        } else {
            if (putchar('.') < 0) {
                goto error_io;
            }
        }
    }

    if (putchar('\n') < 0) {
        goto error_io;
    }

    return fflush(stdout);

error_io:
    return -1;
}

static ssize_t zx_dump_hex(int fd) {
    void *buf;
    ssize_t total = 0;
    int tty = isatty(fileno(stdout));
    struct stat st;

    if (fstat(fd, &st) < 0) {
        goto error_fstat;
    }

    if ((buf = malloc(st.st_blksize)) == NULL) {
        goto error_malloc;
    }

    while (1) {
        ssize_t len, i;
        off_t offset = 0;

        if ((len = read(fd, buf, st.st_blksize)) < 0) {
            goto error_read;
        } else if (len == 0) {
            break;
        }

        for (i=0; i<len; i+=ZX_DUMP_STRIDE_LINE) {
            size_t left   = len - i,
                   linesz = left < ZX_DUMP_STRIDE_LINE?  left: ZX_DUMP_STRIDE_LINE;

            if (hexdump_line(offset, buf, linesz, tty) < 0) {
                goto error_hexdump_line;
            }

            offset += linesz;
            total  += linesz;
        }
    }

    free(buf);

    return total;

error_hexdump_line:
error_read:
    free(buf);

error_malloc:
error_fstat:
    return -1;
}

static inline int zx_print(uint8_t c, int tty) {
    if (ZX_CHAR_LOW(c)) {
        return zx_putchar(c, 0);
    } else if (ZX_CHAR_TOKEN_LOW(c)) {
        return fputs(zx_tokens_low[c - ZX_CHAR_TOKEN_LOW_START], stdout);
    } else if (ZX_CHAR_NEWLINE(c)) {
        return putchar('\n');
    } else if (ZX_CHAR_INVERSE(c)) {
        return zx_putchar(c - ZX_CHAR_INVERSE_START, tty);
    } else if (ZX_CHAR_TOKEN_HIGH(c)) {
        return fputs(zx_tokens[c - ZX_CHAR_TOKEN_HIGH_START], stdout);
    }

    return 0;
}

static ssize_t zx_dump_basic(int fd) {
    void *buf;
    ssize_t total = 0;
    int tty = isatty(fileno(stdout));
    struct stat st;

    if (fstat(fd, &st) < 0) {
        goto error_fstat;
    }

    if ((buf = malloc(st.st_blksize)) == NULL) {
        goto error_malloc;
    }

    if (lseek(fd, ZX_BASIC_STATE_LEN, SEEK_CUR) < 0) {
        goto error_io;
    }

    while (1) {
        ssize_t readlen, len, i;
        zx_basic_line line;
        uint8_t last = 0;

        if ((readlen = read(fd, &line, sizeof(line))) < 0) {
            goto error_io;
        } else if (readlen == 0) {
            break;
        }

        if (printf("%d", (int)be16toh(line.num)) < 0) {
            goto error_io;
        }

        len = le16toh(line.len);

        if (read(fd, buf, len) < 0) {
            goto error_io;
        }

        for (i=0; i<len; i++) {
            uint8_t c = ((uint8_t *)buf)[i];

            if (ZX_CHAR_TOKEN_LOW(c) || ZX_CHAR_TOKEN_HIGH(c)
             || ZX_CHAR_TOKEN_LOW(last) || ZX_CHAR_TOKEN_HIGH(last)) {
                if (putchar(' ') < 0) {
                    goto error_io;
                }
            }

            if (ZX_CHAR_TOKEN_INTEGRAL(c) || ZX_CHAR_TOKEN_FLOAT(c)) {
                i += 5;
            }

            if (zx_print(c, tty) < 0) {
                goto error_io;
            }

            last = c;
        }

        if (!ZX_CHAR_NEWLINE(((uint8_t *)buf)[i-1])) {
            if (putchar('\n') < 0) {
                goto error_io;
            }
        }
    }

    free(buf);

    return total;

error_io:
    free(buf);

error_malloc:
error_fstat:
    return -1;
}

static void usage(const char *prog, char *message, ...) {
    if (message != NULL) {
        va_list args;

        va_start(args, message);
        vfprintf(stderr, message, args);
        fputc('\n', stderr);
        va_end(args);
    }

    fprintf(stderr, "usage: %s [-b] [file]\n", prog);
    exit(1);
}

int main(int argc, char **argv) {
    int fd,
        flags = ZX_DUMP_FLAGS_NONE,
        argn;

    while (1) {
        int c;

        if ((c = getopt(argc, argv, "b")) < 0) {
            break;
        }

        switch (c) {
            case 'b':
                flags |= ZX_DUMP_FLAGS_BASIC;
                break;

            case '?':
            default:
                usage(argv[0], NULL);
        }
    }

    argn = argc - optind;

    if (argn == 0) {
        fd = fileno(stdin);
    } else if (argn == 1) {
        if ((fd = open(argv[optind], O_RDONLY)) < 0) {
            fprintf(stderr, "%s: %s: %s\n", argv[0], argv[optind], strerror(errno));

            goto error_open;
        }
    } else {
        usage(argv[0], "Too many arguments provided");
    }

    if (flags & ZX_DUMP_FLAGS_BASIC) {
        if (zx_dump_basic(fd) < 0) {
            fprintf(stderr, "%s: %s: %s\n",
                    argv[0],
                    (argn == 1)? argv[optind]: "(stdin)",
                    strerror(errno));

            goto error_dump;
        }
    } else {
        if (zx_dump_hex(fd) < 0) {
            fprintf(stderr, "%s: %s: %s\n",
                    argv[0],
                    (argn == 1)? argv[optind]: "(stdin)",
                    strerror(errno));

            goto error_dump;
        }
    }

    if (argn == 1) {
        close(fd);
    }

    return 0;

error_dump:
    if (argn == 1) {
        close(fd);
    }

error_open:
    return 1;
}