/*
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.
*/

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

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

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

// slice is a growable region of bytes in memory
typedef struct slice {
    // ptr is the starting place of the region
    unsigned char* ptr;

    // len is how many bytes are currently being used
    size_t len;

    // cap is how many bytes the memory region has available
    size_t cap;
} slice;

// init_slice is the constructor for type slice
void init_slice(slice* s, size_t cap) {
    s->ptr = malloc(cap);
    s->len = 0;
    s->cap = cap;
}

bool starts_with_bom(const unsigned char* b, const size_t n) {
    return (n >= 3 && b[0] == 0xef && b[1] == 0xbb && b[2] == 0xbf);
}

// handle_reader skips leading UTF-8 BOMs (byte-order marks), and turns all
// CR-LF pairs into single LF bytes
bool handle_reader(FILE* w, FILE* r, slice* line) {
    slice trimmed;

    for (size_t i = 0; !feof(w); i++) {
        int len = getline((char**)&line->ptr, &line->cap, r);
        if (len < 0) {
            break;
        }

        line->len = len;
        trimmed.ptr = line->ptr;
        trimmed.len = line->len;

        // get rid of leading UTF-8 BOM (byte-order mark) if 1st line has it
        if (i == 0 && starts_with_bom(trimmed.ptr, trimmed.len)) {
            trimmed.ptr += 3;
        }

        const unsigned char* p = trimmed.ptr;
        // get rid of trailing line-feeds and CRLF end-of-line byte-pairs
        if (len >= 2 && p[len - 2] == '\r' && p[len - 1] == '\n') {
            trimmed.len -= 2;
        } else if (len >= 1 && p[len - 1] == '\n') {
            trimmed.len--;
        }

        if (fwrite(trimmed.ptr, trimmed.len, 1, w) < 1) {
            return true;
        }
        putc('\n', w);
        fflush(w);
    }

    fflush(w);
    return true;
}

// handle_file handles data from the filename given; returns false only when
// the file can't be opened
bool handle_file(FILE* w, char* fname, slice* line) {
    FILE* f = fopen(fname, "rb");
    if (f == NULL) {
        fprintf(stderr, "\x1b[31mcan't open file named %s\x1b[0m\n", fname);
        return false;
    }

    const bool ok = handle_reader(w, f, line);
    fclose(f);
    return ok;
}

// run returns the number of errors
size_t run(int argc, char** argv, slice* line) {
    size_t dashes = 0;
    for (int i = 1; i < argc; i++) {
        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;
    }

    // use stdin when not given any filepaths
    if (argc <= 1) {
        handle_reader(stdout, stdin, line);
        return 0;
    }

    size_t errors = 0;
    for (int i = 1; i < argc && !feof(stdout); i++) {
        if (argv[i][0] == '-' && argv[i][1] == 0) {
            if (!handle_reader(stdout, stdin, line)) {
                errors++;
            }
            continue;
        }

        if (!handle_file(stdout, argv[i], line)) {
            errors++;
        }
    }

    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);

    slice line;
    init_slice(&line, 16 * 1024);
    if (line.ptr == NULL) {
        char* msg = "\x1b[31mcan't get memory for the line-scanner\x1b[0m\n";
        fprintf(stderr, msg);
        return 1;
    }

    const int res = run(argc, argv, &line) == 0 ? 0 : 1;
    free(line.ptr);
    return res;
}