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

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

#include <dirent.h>
#include <limits.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <errno.h>
#include <unistd.h>

/**
 * Command flags to be used with cp
 */
static struct {
    bool recurse;   /* Recurse copy directorys */
    bool preserve;  /* Preserve file attributes */
    bool sym_link;  /* Symlink files instead of copy */
    bool hard_link; /* Hardlink files instead of copy */
    bool verbose;   /* Verbose the output */
} flags;

/**
 * Help function for cp
 */
static void help(void) {
    printf("Usage: cp [-rplsv] SOURCE... DEST\n\n");
    printf("Copy SOURCEs to DEST\n\n");
    printf("\t-R,-r\tRecurse\n");
    printf("\t-p\tPreserve file attributes if possible\n");
    printf("\t-l,-s\tCreate (sym)links\n");
    printf("\t-v\tVerbose\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':
        case 'r':
            flags.recurse = true;
            break;
        case 'p':
            flags.preserve = true;
            break;
        case 'l':
            flags.hard_link = true;
            flags.sym_link = false;
            break;
        case 's':
            flags.sym_link = true;
            flags.hard_link = false;
            break;
        case 'v':
            flags.verbose = true;
            break;
        default:
            return ARG_INVALID;
    }
    return ARG_UNUSED;
}

/**
 * Takes in two files paths and copies the data from one path to another
 * @param from the file to copy from
 * @param to the file to copy to
 * @returns if the file successfully coppied
 */
static bool copy_file(char* from, char* to) {
    #define BS 1024 /* The block size of copy with */
    
    FILE *from_f, *to_f; /* file pointers to cope data from and to */
    char buf[BS]; /* te file copy buffer */
    int read; /* the amount of bytes read */

    /* attempt to get a read stream from the src file */
    from_f = get_file_s(from, "r");
    if (from_f == NULL) { return false; }

    /* attempt to get a write streams from the dest file */
    to_f = get_file_s(to, "w");
    if (to_f == NULL) { fclose(from_f); return false; }

    /* while data is read copy the data to the dest */
    while ((read = fread(buf, 1, BS, from_f)) > 0) {
        fwrite(buf, 1, read, to_f);
    }

    /* output if verbose */
    if (flags.verbose) {
        output("copied '%s'", from);
    }

    return true;
}

/**
 * Takes in two file paths and symlinks from one to the other path
 * @param from the file to symlink
 * @param to the path to put the symlink
 * @returns if the file successfully symlinked
 */
static bool symlink_file(char* from, char* to) {
    /* symlink the file and error if failed */
    if (symlink(from, to) < 0) {
        error_s("failed to symlink '%s'", from);
        return false;
    } else if (flags.verbose) {
        output("symlinked '%s'", from); /* output if verbose */
    }
    return true;
}

/**
 * Takes in two file paths and hardlinks from one to the other path
 * @param from the file to hardlink
 * @param the path to put the hardlink
 * @returns fi the fule successfully hardlinked
 */
static bool hardlink_file(char* from, char* to) {
    /* hard link the file and error if failed */
    if (link(from, to) < 0) {
        error_s("failed to hardlink '%s'", from);
        return false;
    } else if (flags.verbose) {
        output("hardlinked '%s'", from); /* output if verbose */
    }
    return true;
}

/**
 * Copies data from one path to another using the set path buffers and
 * flags. Make sure to set these before running this function.
 * @param s the stat of the file being coppied
 */
static void run_copy(struct stat* s) {

    /* read file paths from the path buffers */
    char* from = get_path_buffer();
    char* to = get_path_buffer_2();

    /* choose copy method based on given flags */
    bool result;
    if (flags.sym_link) { 
        result = symlink_file(from, to); /* symlink */
    } else if (flags.hard_link) {
        result = hardlink_file(from, to); /* hardlink */
    } else {
        result = copy_file(from, to); /* copy */
    }

    /* if failed return */
    if (!result) return;
    if (!flags.preserve) return;

    /* if set to preserve file attribs, copy over ownership and permissions */
    if (chmod(to, s->st_mode) < 0) {
        error_s("cannot chmod '%s'", to); /* error if failed */
        return;
    }

    if (chown(to, s->st_uid, s->st_gid) < 0) {
        error_s("cannot chown '%s'", to); /* error if failed */
        return;
    }
}

/* predefine function definition */
static void cp_file(char* path);
    
/**
 * Copies all files in a diretory specified in the path buffer, to the dest.
 * Make sure both the src and dest path buffers are set before calling.
 * @param s the stat of the directory
 */
static void cp_directory(struct stat* s) {
    
    DIR* d;
    struct dirent* file;

    /* if were not recursing ignore directory and error */
    if (!flags.recurse) {
        error_s("-r not specified; omitting directory '%s'", get_path_buffer());
        return;
    }

    /* if we failed to make the directory to copy data into error and return */
    if (mkdir(get_path_buffer_2(), s->st_mode) < 0 && errno != EEXIST) {
        error_s("cannot create directory '%s'", get_path_buffer_2());
        return;
    }

    /* open directory, if failed error and return */
    d = opendir(get_path_buffer());
    if (d == NULL) {
        error_s("cannot open directory '%s'", get_path_buffer());
        return;
    }

    /* copy each file in the directory */
    while ((file = readdir(d)) != NULL) {
        if (is_dot_dir(file->d_name)) continue;
        cp_file(file->d_name);
    }
}

/**
 * Copies a given file path to the destination given in the 2nd path buffer
 * Make sure path buffer 2 is set before running this function
 * @param path the file to copy
 */
static void cp_file(char* path) {
    
    /* load src and dest into path buffers */
    int save = push_path_buffer(path);
    int save2 = push_path_buffer_2(get_last_component(path));
   
    /* if we cannot get file info error and return */
    struct stat s;
    if (lstat(get_path_buffer(), &s) < 0) {
        pop_path_buffer(save);
        error_s("cannot stat '%s'", get_path_buffer());
        return;
    }
    
    /* if the file is a directory copy it as a directory, else copy it as a file */
    if (S_ISDIR(s.st_mode)) {
        cp_directory(&s);
    } else {
        run_copy(&s);
    }
    
    /* cleanup */
    pop_path_buffer(save);
    pop_path_buffer_2(save2);
}

/**
 * Copes file from a src path to a dest path
 */
COMMAND(cp_main) {

    int start, i;
    struct stat s;

    /* define default flags */
    flags.hard_link = false;
    flags.sym_link = false;
    flags.preserve = false;
    flags.recurse = false;
    flags.verbose = false;

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

    /* if not enough arguments passed show help message and quit */
    if (argc - start < 2) {
        global_help(help);
    }

    /* only when 2 args and first is a file, the 2nd will be a file */
    if (argc - start == 2) {

        /* if cannot read file info error and exit */
        struct stat s;
        if (lstat(argv[start], &s) < 0) {
            error("cannot stat '%s'", argv[start]);
        }

        /* load src and dest into path buffers */
        push_path_buffer(argv[argc-2]);
        push_path_buffer_2(argv[argc-1]);

        /* if the file is a directory copy it as a directory, else copy it as a file */
        if (!S_ISDIR(s.st_mode)) {
            run_copy(&s);
        } else {
            cp_directory(&s);
        }

        /* no need to cleanup path buffers since command is done */

        return EXIT_SUCCESS;
    }

    /* otherwise treat the dest argument as a directory */
 
    /* push dest directory */
    push_path_buffer_2(argv[argc-1]);

    /* if we cannot read dest info error and return */
    if (lstat(get_path_buffer_2(), &s) < 0) {
        error("target: '%s'", get_path_buffer_2());
    }

    /* copy each file into dest directory */
    for (i = start; i < argc - 1; i++) {
        cp_file(argv[i]);
    }

    return EXIT_SUCCESS;
}