/**
 *  file: chmod.c
 *  command: chmod
 *  author: Tyler Murphy
 */

#include "command.h"
#include "lslib.h"

#include <stdlib.h>
#include <sys/types.h>
#include <pwd.h>
#include <unistd.h>
#include <dirent.h>
#include <string.h>

/**
 * If to add remove or directly set bits to a file
 */
enum method {
    ADD,
    SUB,
    SET
};

/**
 * Flags to set in chmod
 */
static struct {
    bool recurse;           /* if to recurse directorys */
    bool list_changed;      /* if to list what was updated */
    bool verbose;           /* if to list all output */
    bool quiet;             /* if to silence errors */
    enum method method;     /* the method to apply to the mode */
    mode_t mode;            /* the mode to apply with the method */
} flags;

/**
 * Help function for chmod
 */
static void help (void) {
    printf("Usage: chmod [-Rcvf] MODE[,MODE]... FILE...\n\n");
    printf("MODE is octal number (bit pattern sstrwxrwxrwx) or {+|-|=}[rwxXst]\n\n");
    printf("\t-R\tRecurse\n");
	printf("\t-c\tList changed files\n");
	printf("\t-v\tVerbose\n");
	printf("\t-f\tHide errors\n");
}

/** 
 * Takes in each argument that has a single - and parses it 
 * @param c the character after the -
 * @param next the next argument in argv that hasnt been parsed
 * @reutrn if the next arg was used or if the arg was invalid
 */
static int short_arg(char c, char* next) {
    UNUSED(next);
    switch (c) {
        case 'R':
            flags.recurse = true;
            break;
        case 'c':
            flags.list_changed = true;
            break;
        case 'v':
            flags.verbose = true;
            break;
        case 'f':
            flags.quiet = true;
            break;
        case 'r':
        case 'w':
        case 'x':
        case 'X':
        case 't':
        case 's':
            return ARG_IGNORE;
        default:
            return ARG_INVALID;
    }
    return ARG_UNUSED;
}

/** 
 * Given a file path, modify its mode, and recurse if set to
 * @param path the file path to modify
 */
static void chmod_file(char* path) {
    /* allocate arguments on stack */
    int save; /* path buffer save */
    struct stat s; /* file info */
    DIR* d; /* if recursing, open dir */
    struct dirent* file; /* if recursing, file being read */
    mode_t mode = 0; /* silence the uninitalized var error */

    /* add path to path buffer */
    save = push_path_buffer(path);
    
    /* get file statics, if failed return */
    if (lstat(get_path_buffer(), &s) < 0) {
        if (!flags.quiet) {
            error_s("cannot stat '%s'", get_path_buffer()); /* error if failed */
        }
        pop_path_buffer(save);
        return;
    }

    /* get the new mode given the method and proved mode */
    if (flags.method == SET) {
        mode = flags.mode;;
    } else if (flags.method == ADD) {
        mode = s.st_mode | flags.mode;
    } else if (flags.method == SUB) {
        mode = s.st_mode & ~flags.mode;
    }
    
    /* attempt to modify the file mode, error and return if failed */
    if (chmod(get_path_buffer(), mode) < 0) {
        if (!flags.quiet) {
            error_s("cannot chmod '%s'", get_path_buffer()); /* error if failed */
        }
        pop_path_buffer(save); /* clean up */
        return;
    } else if (flags.list_changed) {
        output("changed '%s' to %o", get_path_buffer(), mode); /* print if set to be verbose */
    }

    /* if not set to recurse, dont bother to do future checks */
    if (!flags.recurse) {
        pop_path_buffer(save);
        return;
    }

    /* if not a dir, cant recurse and then return */
    if (!S_ISDIR(s.st_mode)) {
        pop_path_buffer(save);
        return;
    }

    /* get the directory, if failed, error and return */
    d = opendir(get_path_buffer());
    if (d == NULL) {
        if (!flags.quiet) {
            error_s("cannot open dir '%s'", get_path_buffer()); /* error if failed */
        }
        pop_path_buffer(save); /* clean up */
        return;
    }

    /* chmod each file read */
    while ((file = readdir(d)) != NULL) {
        if (is_dot_dir(file->d_name)) continue; /* ignore dot dirs */
        chmod_file(file->d_name);
    }
    
    /* clean up */
    closedir(d);
    pop_path_buffer(save);
}

/**
 * Parse a given mode and its method
 * @param input a pointer to the string to check
 * @return the mode parsed, mode parsing could not be done if reached , if so call again
 */
static mode_t parse_mode(char** input) {
    mode_t mode = 00000; /* default mode */
    char* str = *input; /* get the input string */

    /* check method for mode */
    switch (*str) {
        case '=':
            flags.method = SET;
            break;
        case '+':
            flags.method = ADD;
            break;
        case '-':
            flags.method = SUB;
            break;
        default:
            flags.method = SET;
            mode = get_mode(str); /* get mode and skip next checks */
            goto end;
    }

next: /* check what bits to update */
    str++;
    switch (*str) {
        case 'r':   /* read */
            mode |= 00444;
            goto next;
        case 'w':   /* read */
            mode |= 00200;
            goto next;
        case 'x':   /* execute */
            mode |= 00111;
            goto next;
        case 'X':   /* empty */
            mode |= 00000;
            goto next;
        case 's':   /* setuid and setgid */
            mode |= 06000;
            goto next;
        case 't':   /* sticky */
            mode |= 01000;
            goto next;
        case '\0':
        case ',':    /* stop reading args */
            goto end;
        default:
            error("invalid option: %c", *str); /* error when invalid */
    }

end: /* read till next argument and update input string pointer */

    while (true) {
        
        if (*str == '\0') {
            *input = NULL; /* no mroe args */
            break;
        }

        if (*str == ',') {
            *input = ++str; /* another argument found */
            break;
        }

        str++;
    }

    return mode; /* return mode */
}

/**
 * Modify a files permission mode
 */
COMMAND(chmod_main) {
    
    int start, i; 
    
    /* get default flags */
    flags.recurse = false;
    flags.list_changed = false;
    flags.verbose = false;
    flags.quiet = false;
    flags.mode = 0;

    /* parse arguments */
    start = parse_args(argc, argv, help, short_arg, NULL);

    /* if not arguments error and return */
    if (argc - start < 1) {
        if (!flags.quiet) {
            error("no mode provided");
        } else {
            return EXIT_FAILURE;
        }
    }

    /* parse mode continusally until no more mode arguments found */
    do {
        flags.mode |= parse_mode(&argv[start]);
    } while (argv[start] != NULL);

    /* if no files found error and return */
    if (argc - start < 2) {
        if (!flags.quiet) {
            error("no files passed");
        } else {
            return EXIT_FAILURE;
        }
    }

    /* for each file passed, chmod */
    for (i = start + 1; i < argc; i++) {
        chmod_file(argv[i]);
    }

    return EXIT_SUCCESS; /* return */
}