#include "../command.h"

#include <ctype.h>
#include <errno.h>
#include <string.h>
#include <sys/stat.h>

struct Flags {
    bool number_lines;
    bool number_non_empty;
    bool change_non_print;
    bool change_tabs;
    bool end_lines_dollar;
};

static bool printable(char c) {
    switch (c) {
        case '\n': return true;
        case '\r': return true;
        case '\b': return true;
        case '\t': return true;
        default: return isprint(c);
    }
}

static void help() {
    printf("Usage: cat [-nbvteA] [FILE]...\n\n");
    printf("Print FILEs to stdout\n\n");
    printf("-n	Number output lines\n");
    printf("-b	Number nonempty lines\n");
    printf("-v	Show nonprinting characters as ^x or M-x\n");
    printf("-t	...and tabs as ^I\n");
    printf("-e	...and end lines with $\n");
    printf("-A	Same as -vte\n");
    exit(EXIT_SUCCESS);
}

static void cat_file(FILE* file, struct Flags flags) {
    char c;
    size_t read;
    
    size_t line = 1;
    bool empty = true;
    bool newline = true;
    
    while ((read = fread(&c, 1, 1, file)) != 0) {
        if (c == '\n') {
            if (empty && flags.number_lines) {
                printf("\t%ld ", line);
            }
            if (flags.end_lines_dollar) {
                printf("$");
            }
            line++;
            newline = true;
            empty = true;
            goto print;
        } else {
            empty = false;
        }

        if (!newline) {
            goto print;
        }

        if (!empty && (flags.number_non_empty || flags.number_lines)) {
            printf("\t%ld ", line);
            newline = false;
        }
    print:
        if (!flags.change_non_print || printable(c)) {
            if (flags.change_tabs && c == '\t') {
                fwrite("^I", 1, 2, stdout);
            } else {
                fwrite(&c, 1, 1, stdout);
            }
        } else {
            c |= '@';
            fwrite(&c, 1, 1, stdout);
        }
    }
}

COMMAND(cat) {

    struct Flags flags;
    flags.number_lines = false;
    flags.number_non_empty = false;
    flags.change_non_print = false;
    flags.change_tabs = false;
    flags.end_lines_dollar = false;

    for (int i = 0; i < argc; i++) {
        if (!prefix("-", argv[i])) {
            continue;
        }

        if (streql("--help", argv[i])) {
            help();
        }

        size_t len = strlen(argv[i] + 1);
        for (size_t j = 0; j < len; j++) {
            char c = argv[i][j + 1];
            switch (c) {
                case 'n':
                    flags.number_lines = true;
                    break;
                case 'b':
                    flags.number_non_empty = true;
                    break;
                case 'v':
                    flags.change_non_print = true;
                    break;
                case 't':
                    flags.change_non_print = true;
                    flags.change_tabs = true;
                    break;
                case 'e':
                    flags.change_non_print = true;
                    flags.end_lines_dollar = true;
                    break;
                case 'A':
                    flags.change_non_print = true;
                    flags.change_tabs = true;
                    flags.end_lines_dollar = true;
                    break;
                default:
                    error("error: unkown flag -%c", c);
            }
        } 
    }

    bool files = false;
    for (int i = 0; i < argc; i++) {
        if (streql("-", argv[i])) {
            files = true;
            cat_file(stdin, flags);
        } else if (prefix("-", argv[i])) {
            continue;
        } else {
            files = true;
            struct stat s;
            if (stat(argv[i], &s) < 0) {
                printf("error: failed to read %s: %s\n", argv[i], strerror(errno));
                continue;
            }
            if (!S_ISREG(s.st_mode)) {
                printf("error: %s is not a file\n", argv[i]);
                continue;
            }
            FILE* in = get_file(argv[i], "r");
            cat_file(in, flags);
            fclose(in);
        }
    }

    if (!files) {
        cat_file(stdin, flags);
    }
    
    return EXIT_SUCCESS;
}