#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 <errno.h>

#define ZXDUMP_STRIDE_LINE 16
#define ZXDUMP_STRIDE_GROUP 2
#define ZXDUMP_CHARSET_LEN 64

static uint16_t charset[ZXDUMP_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 void usage(int argc, char **argv, 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 file\n", argv[0]);
    exit(1);
}

static inline size_t utf8_encode(uint8_t *buf, uint16_t codepoint) {
    if ((codepoint & 0x007f) == codepoint) {
        buf[0] = codepoint & 0xff;
        return 1;
    } else if ((codepoint & 0x07ff) == codepoint) {
        buf[0] = (codepoint & 0x07c0) >> 6;
        buf[1] =  codepoint & 0x003f;
        return 2;
    } else if ((codepoint & 0xffff) == codepoint) {
        buf[0] = (codepoint & 0xf000) >> 12;
        buf[1] = (codepoint & 0x0fc0)  >>  6;
        buf[2] =  codepoint & 0x003f;
        return 3;
    }
}

static ssize_t dump_line(off_t offset, void *buf, size_t len) {
    size_t i;

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

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

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

    if (printf("  ") < 0) {
        goto error_io;
    }

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

        if (c < ZXDUMP_CHARSET_LEN) {
            uint16_t codepoint = charset[c];
            uint8_t sequence[4];

            size_t len = utf8_encode(sequence, codepoint);

            /* XXX: Implement support for inverse colours */
            if (fwrite(sequence, len, 1, stdout) < 1) {
                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 dump_fd(int fd) {
    void *buf;
    ssize_t offset = 0;
    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;

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

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

            if (dump_line(offset, buf, linesz) < 0) {
                goto error_dump_line;
            }

            offset += linesz;
        }
    }

    free(buf);

    return offset;

error_dump_line:
error_read:
    free(buf);

error_malloc:
error_fstat:
    return -1;
}

int main(int argc, char **argv) {
    int fd;

    if (argc == 1) {
        fd = fileno(stdin);
    } else if (argc == 2) {
        if ((fd = open(argv[1], O_RDONLY)) < 0) {
            goto error_open;
        }
    } else {
        usage(argc, argv, "Too many arguments provided");
    }

    if (dump_fd(fd) < 0) {
        fprintf(stderr, "%s: %s: %s\n",
                argv[0],
                (argc == 2)? argv[1]: "(stdin)",
                strerror(errno));

        goto error_dump_fd;
    }

    if (argc == 2) {
        close(fd);
    }

    return 0;

error_dump_fd:
    if (argc == 2) {
        close(fd);
    }

error_open:
    return 1;
}