/*
The MIT License (MIT)

Copyright © 2024 pacman64

Permission is hereby granted, free of charge, to any person obtaining a copy of
this software and associated documentation files (the “Software”), to deal
in the Software without restriction, including without limitation the rights to
use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
of the Software, and to permit persons to whom the Software is furnished to do
so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.
*/

/*
coby [files...]


COunt BYtes finds out some simple byte-related stats, counting

    - bytes
    - runes, which are UTF-8 code-points
    - lines
    - how many lines have trailing spaces
    - how many lines end with a CRLF pair
    - all-off (0) bytes
    - all-on (255) bytes
    - high-bytes (128+)
    - which (if any) byte-order mark the data start with

The output is TSV (tab-separated values) lines, where the first line has
all the column names.

When no filepaths are given, the standard input is used by default.
*/

/*
You can build this command-line app by running
    cc -Wall -s -O2 -o ./coby ./coby.c
*/

#include <fcntl.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#ifdef _WIN32
#include <windows.h>
#endif

const char* header = ""
    "name\tbytes\trunes\tlines\tlf\tcrlf\tspaces\ttabs"
    "\ttrails\tnulls\tfulls\thighs\tbom";

enum {
    no_bom = 0,
    utf8_bom = 1,
    utf16le_bom = 2,
    utf16be_bom = 3,
    utf32le_bom = 4,
    utf32be_bom = 5,
};

const char* bom_legend[] = {
    "",
    "UTF-8",
    "UTF-16 LE",
    "UTF-16 BE",
    "UTF-32 LE",
    "UTF-32 BE",
};

// stats holds all byte-related counts this app deals with
typedef struct stats {
    uint64_t bytes;  // the total byte-count
    uint64_t runes;  // how many utf-8 items
    uint64_t lines;  // how many plain-text lines
    uint64_t lf;     // how many line-feeds
    uint64_t crlf;   // how many carriage-return/line-feed pairs
    uint64_t spaces; // how many spaces
    uint64_t tabs;   // how many tabs
    uint64_t trails; // how many plain-text lines with trailing spaces
    uint64_t nulls;  // how many all-bits-off bytes
    uint64_t fulls;  // how many all-bits-on bytes
    uint64_t highs;  // how many bytes with the highest-order bit on
    uint64_t bom;    // which (if any) kind of byte-order mark data start with
} stats;

uint64_t check_bom(unsigned char* data, size_t len) {
    const unsigned char* d = data;

    if (len >= 3 && data[0] == 0xef && data[1] == 0xbb && data[2] == 0xbf) {
        return utf8_bom;
    }
    if (len >= 4 && d[0] == 0xff && d[1] == 0xfe && d[2] == 0 && d[3] == 0) {
        return utf32le_bom;
    }
    if (len >= 4 && d[0] == 0 && d[1] == 0 && d[2] == 0xfe && d[3] == 0xff) {
        return utf32be_bom;
    }
    if (len >= 2 && data[0] == 0xff && data[1] == 0xfe) {
        return utf16le_bom;
    }
    if (len >= 2 && data[0] == 0xfe && data[1] == 0xff) {
        return utf16be_bom;
    }

    return no_bom;
}

// count_bytes gathers all sorts of byte-related stats, besides a total count
void count_bytes(FILE* r, stats* res) {
    unsigned char buf[48 * 1024];
    uint64_t tally[256];

    uint64_t bytes = 0;
    uint64_t crlf = 0;
    uint64_t trails = 0;
    uint64_t runes = 0;

    unsigned char prev2 = 0;
    unsigned char prev1 = 0;

    memset(tally, 0, sizeof(tally));
    memset(res, 0, sizeof(stats));

    while (true) {
        const size_t len = fread(buf, sizeof(unsigned char), sizeof(buf), r);

        if (len < 1) {
            break;
        }

        if (bytes == 0) {
            res->bom = check_bom(buf, len);
        }
        bytes += len;

        for (size_t i = 0; i < len; i++) {
            const unsigned char cur = buf[i];
            tally[cur]++;

            crlf += (prev1 == '\r') && (cur == '\n');
            trails += (cur == '\n') &&
                ((prev1 == ' ') || (prev2 == ' ' && prev1 == '\r'));
            runes += (cur & 0xc0) != 0x80;

            prev2 = prev1;
            prev1 = cur;
        }
    }

    res->bytes = bytes;
    res->crlf = crlf;
    res->trails = trails;
    res->runes = runes;

    res->lines = tally['\n'];
    res->lf = tally['\n'];
    res->spaces = tally[' '];
    res->tabs = tally['\t'];
    res->nulls = tally[0];
    res->fulls = tally[255];

    res->highs = 0;
    for (size_t i = 128; i < 256; i++) {
        res->highs += tally[i];
    }

    // count last line for non-empty inputs not ending with a line-feed byte
    if (res->bytes > 0 && prev1 != '\n') {
        res->lines++;
    }

    // count last trail for inputs not ending with a line-feed byte
    if (prev1 == ' ' || (prev2 == ' ' && prev1 == '\r')) {
        res->trails++;
    }
}

// handle_input gathers stats, and shows a TSV line out of the results
void handle_input(FILE* r, stats* res, char* name) {
    // show the filename right away, to reassure users something's happening
    printf("%s", name);
    fflush(stdout);

    count_bytes(r, res);

    // show results as soon as they're available
    printf("\t%lu\t%lu\t%lu\t%lu\t%lu\t%lu\t%lu\t%lu\t%lu\t%lu\t%lu\t",
        res->bytes, res->runes, res->lines, res->lf, res->crlf, res->spaces,
        res->tabs,res->trails, res->nulls, res->fulls, res->highs);
    printf("%s\n", bom_legend[res->bom]);
    fflush(stdout);
}

// handle_file handles data from the filename given, and returns whether the
// file was opened successfully
bool handle_file(char* fname, stats* res) {
    FILE* f = fopen(fname, "rb");
    if (f == NULL) {
        fprintf(stderr, "\x1b[31mcan't open file named %s\x1b[0m\n", fname);
        return false;
    }

    handle_input(f, res, fname);
    fclose(f);
    return true;
}

// run returns the number of errors
size_t run(int argc, char** argv) {
    size_t empty = 0;
    size_t dashes = 0;

    for (int i = 1; i < argc; i++) {
        if (argv[i][0] == 0) {
            empty++;
            continue;
        }

        if (argv[i][0] == '-' && argv[i][1] == 0) {
            dashes++;
        }
    }

    if (dashes > 1) {
        const char* msg = "can't use a dash (stdin) as input more than once";
        fprintf(stderr, "\x1b[31m%s\x1b[0m\n", msg);
        return 1;
    }

    // show header line right away, to reassure users the app is working
    printf("%s\n", header);
    fflush(stdout);

    // if output is done, don't even bother doing anything
    if (feof(stdout)) {
        return 0;
    }

    // use stdin when not given any filepaths, or when all paths are empty
    if (argc <= 1 || empty == argc - 1) {
        stats res;
        handle_input(stdin, &res, "-");
        return 0;
    }

    stats res;
    size_t errors = 0;

    for (int i = 1; i < argc; i++) {
        // if output is done while being piped, quit right away
        if (feof(stdout)) {
            return errors;
        }

        // ignore empty names
        if (argv[i][0] == 0) {
            continue;
        }

        // handle `-` as stdin
        if (argv[i][0] == '-' && argv[i][1] == 0) {
            handle_input(stdin, &res, argv[i]);
            continue;
        }

        errors += !handle_file(argv[i], &res);
    }

    return errors;
}

int main(int argc, char** argv) {
#ifdef _WIN32
    setmode(fileno(stdin), O_BINARY);
    // ensure output lines end in LF instead of CRLF on windows
    setmode(fileno(stdout), O_BINARY);
    setmode(fileno(stderr), O_BINARY);
#endif

    // disable automatic stdio buffering, in favor of explicit buffering
    setvbuf(stdin, NULL, _IONBF, 0);
    setvbuf(stdout, NULL, _IONBF, 0);
    setvbuf(stderr, NULL, _IONBF, 0);

    return run(argc, argv) == 0 ? 0 : 1;
}