/**
 *  file: ls.c
 *  author: Tyler Murphy
 */

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

#include <grp.h>
#include <pwd.h>
#include <dirent.h>
#include <ftw.h>
#include <limits.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <sys/stat.h>
#include <unistd.h>
#include <sys/ioctl.h>

/* quirky colors */
#define FILE_COLOR      ANSCII BLACK COLOR
#define DIR_COLOR       ANSCII BOLD NEXT NORMAL BLUE COLOR
#define DIR_COLOR_EXEC  ANSCII BACKGROUND GREEN  NEXT NORMAL BLACK COLOR
#define LINK_COLOR      ANSCII BOLD NEXT NORMAL TURQUOISE COLOR
#define SET_UID_COLOR   ANSCII BACKGROUND RED NEXT NORMAL WHITE COLOR
#define SET_GID_COLOR   ANSCII BACKGROUND YELLOW NEXT NORMAL BLACK COLOR
#define EXEC_COLOR      ANSCII BOLD NEXT NORMAL GREEN COLOR
#define BLK_COLOR       ANSCII BOLD NEXT NORMAL YELLOW COLOR
#define SOCK_COLOR      ANSCII BOLD NEXT NORMAL MAGENTA COLOR

/**
 * Describes when to do something
 */
enum When {
    YES, /* always */
    NO, /* never */
    AUTO /* when not tty */
};

/**
 * Flags that are to be used with ls
 */
static struct {
    bool hidden;        /* -a if to show hidden files */
    bool hide_dot;      /* -A if to hide dot dirs */
    bool more_info;     /* -l if to print info as a long list */
    bool one_column;    /* -1 if to print files as a single column */
    bool recurse;       /* -R if to recurse directorys */
    bool octets;        /* -o if to print mode as its octet instead of romanized */
    enum When colored;  /* --color=never/no/yes/always/auto */
} flags;

/** 
 * Keeps track of the files data
 */
struct FileInfo {
    struct passwd* usr; /* the files owner user */
    struct group* grp;  /* the files owner group */
    char* name;         /* the file name */
    char date[13];      /* the files romanized date */
    char mode[11];      /* the files mode romanized or octets */
    char size[5];       /* the human readable file size */
    int links;          /* the amount of inode links */
    int bytes;          /* the amount of bytes in the file*/
    bool set_uid;       /* if the file is set uid */
    bool set_gid;       /* if the file is set gid */
    bool exec;          /* if the binary is executable by the user running ls */
    unsigned char type; /* the type of the file */
};

/**
 * Keeps track of the biggest data to make the output data look pretty
 */
struct FileListInfo {
    int max_link;
    int max_usr;
    int max_grp;
    int max_size;
    int max_name;
    int total_len;
    int total_size;
};

/** 
 * Gets a directory and fails if it cannot be opened
 * @param path the path to the directory
 * @returns the directory if found or NULL if not
 */
static DIR* get_directory(char* path) {
    DIR* d = opendir(path);
    if (d == NULL) {
        if (errno == ENOTDIR) {
            error_s("`%s` is a a file", path);
        } else {
            error_s("failed to open directory '%s'", path);
        }
    }
    return d;
}

/**
 * Takes in a file and parses its mode to be humand readable
 * @param info the file infomation to store the mode into
 * @param mode the octet form of the mode
 * @param type the type of the file
 */
static void parse_file_mode(struct FileInfo* info, mode_t mode, int type) {
    switch (type) {
        case DT_BLK:
            info->mode[0] = 'b'; /* block device */
            break;
        case DT_CHR:
            info->mode[0] = 'c'; /* something i dunno */
            break;
        case DT_DIR:
            info->mode[0] = 'd'; /* directory */
            break;
        case DT_FIFO:
            info->mode[0] = 'f'; /* fifo */
            break;
        case DT_LNK:
            info->mode[0] = 'l'; /* symlink */
            break;
        case DT_SOCK:
            info->mode[0] = 's'; /* socket */
            break;
        case DT_UNKNOWN:
            info->mode[0] = 'u'; /* unkown (eye emoji) */
            break;
        case DT_WHT:
            info->mode[0] = 'w'; /* tf, wheat? idk */
            break;
        default:
            info->mode[0] = '-'; /* regular file */
            break;
    }
    
    /* parse info for the user bits */
    info->mode[1] = (mode & S_IRUSR) ? 'r' : '-';
    info->mode[2] = (mode & S_IWUSR) ? 'w' : '-';
    if (mode & S_IXUSR && mode & S_ISUID) {
        info->mode[3] = 's';
    } else if (mode & S_ISUID) {
        info->mode[3] = 'S';
    } else if (mode & S_IXUSR) {
        info->mode[3] = 'x';
    } else {
        info->mode[3] = '-';
    }

    /* parse info for the group bits */
    info->mode[4] = (mode & S_IRGRP) ? 'r' : '-';
    info->mode[5] = (mode & S_IWGRP) ? 'w' : '-';
    if (mode & S_IXGRP && mode & S_ISGID) {
        info->mode[6] = 's';
    } else if (mode & S_ISGID) {
        info->mode[6] = 'S';
    } else if (mode & S_IXGRP) {
        info->mode[6] = 'x';
    } else {
        info->mode[6] = '-';
    }

    /* parse info for the other bits */
    info->mode[7] = (mode & S_IROTH) ? 'r' : '-';
    info->mode[8] = (mode & S_IWOTH) ? 'w' : '-';
    if (mode & S_IXOTH && mode & S_ISVTX) {
        info->mode[9] = 't';
    } else if (mode & S_ISVTX) {
        info->mode[9] = 'T';
    } else if (mode & S_IXOTH) {
        info->mode[9] = 'x';
    } else {
        info->mode[9] = '-';
    }

    /* make a null terminated string */
    info->mode[10] = '\0';
}

/**
 * Gets information about a given file_name in a directory and 
 * stores it into a fileinfo struct
 * @param file_name the name of the file in the directory currently
 *          stored in the path buffer
 * @param info the file info struct to store the data into
 * @returns if successfull in reading the file
 */
static bool get_file_info(const char* file_name, struct FileInfo* info) {

    uid_t uid;
    gid_t gid;
    int save, ty;
    struct stat s;
    size_t file_len;

    uid = getuid();
    gid = getgid();

    /* default to all false */
    memset(&s, 0, sizeof(struct stat));

    /* push the file to the path buffer to stat */
    save = push_path_buffer(file_name);

    /* get file stats */
    if (lstat(get_path_buffer(), &s) < 0) {
        error_s("failed to read file '%s'", get_path_buffer());
        pop_path_buffer(save);
        return false;
    }

    /* get file type */
    ty = (s.st_mode & S_IFMT) >> 12;

    /* parse long list mode as octets or human readable */
    if (flags.octets) {
        info->mode[0] = '0' + (s.st_mode / (8 * 8 * 8) % 8);
        info->mode[1] = '0' + (s.st_mode / (8 * 8 * 1) % 8);
        info->mode[2] = '0' + (s.st_mode / (8 * 1 * 1) % 8);
        info->mode[3] = '0' + (s.st_mode / (1 * 1 * 1) % 8);
        info->mode[4] = '\0';
    } else {
        parse_file_mode(info, s.st_mode, ty);
    }

    /* check if the file is executable by the user */
    if (
        (s.st_mode & S_IXUSR && s.st_uid == uid) ||
        (s.st_mode & S_IXGRP && s.st_gid == gid) ||
        s.st_mode & S_IXOTH
    ) {
        info->exec = true;
    } else {
        info->exec = false;
    }
    
    /* get setuid and setgid bits */
    info->set_uid = s.st_mode & S_ISUID;
    info->set_gid = s.st_mode & S_ISGID;

    /* get user information */
    info->usr = getpwuid(s.st_uid);
    if (info->usr == NULL) {
        error_s("failed to get user id: `%s`", get_path_buffer());
        pop_path_buffer(save);
        return false;
    }

    /* get group information */
    info->grp = getgrgid(s.st_gid);
    if (info->grp == NULL) {
        error_s("failed to get user id: `%s`", get_path_buffer());
        pop_path_buffer(save);
        return false;
    }

    /* update inode links and file type */
    info->links = s.st_nlink;
    info->type = ty;

    /* copy the file name into the info */
    file_len = strlen(file_name) + 1;
    info->name = xalloc(file_len);
    memcpy(info->name, file_name, file_len);

    /* get the date and time for the file */
    print_file_size(s.st_size, info->size);
    print_date_time(s.st_mtim.tv_sec + s.st_mtim.tv_nsec / 1000000000, info->date);
    
    /* convert the bytes into human readable */
    info->bytes = (s.st_size + s.st_blksize - 1) / s.st_blksize;

    /* cleanup */
    pop_path_buffer(save);
    return true;
}

/**
 * Gets the file color from its mode
 * @pram info the file info to get the color from
 * @return the anscii escape code for the file color
 */
static char* get_file_color(struct FileInfo* info) {
    char* color;
    if (info->type == DT_DIR) {
        if (info->mode[8] == 'w') {
            color = DIR_COLOR_EXEC; /* directory is green if anyone can write it */
        } else {
            color = DIR_COLOR; /* other whise as the french say it, bleu */
        }
    } else if (info->type == DT_LNK) {
        color = LINK_COLOR; /* symlink color */
    } else if (info->type == DT_SOCK) {
        color = SOCK_COLOR; /* sockt color */
    } else if (
        info->type == DT_CHR || 
        info->type == DT_BLK
    ) {
        color = BLK_COLOR; /* the weird ones are yellow, cool */
    } else {
        if (info->set_uid) {
            color = SET_UID_COLOR; /* hightlighted red if setuid */
        } else if (info->set_gid) {
            color = SET_GID_COLOR; /* highlighted yellow if setgid and not setuid */
        } else if (info->exec) {
            color = EXEC_COLOR; /* green if executable */
        } else {
            color = FILE_COLOR; /* white if basic and boring */
        }
    }
    return color;
}

/**
 * Lists a file in long info mode
 * @param info the global info for a directory
 * @param finfo the file specific info
 */
static void list_file_long(struct FileListInfo* info, struct FileInfo* finfo) {
    char* color;

    color = get_file_color(finfo);
    
    printf("%s %*d %*s %*s %*s %s %s%s%s", /* print data */
        finfo->mode, 
        info->max_link,
        finfo->links,
        info->max_usr,
        finfo->usr->pw_name,
        info->max_grp,
        finfo->grp->gr_name, 
        info->max_size,
        finfo->size, 
        finfo->date,
        flags.colored != NO ? color : "", /* if not colored dont color */
        finfo->name,
        flags.colored != NO ? "\x1b[0m" : ""
    );

    /* if it is a symlink, add the path where it points to */
    if (finfo->type == DT_LNK) {
        int save = push_path_buffer(finfo->name); 

        /* get the link */
        char lnk[PATH_MAX];
        ssize_t n;
        if ((n = readlink(get_path_buffer(), lnk, PATH_MAX)) != -1) {
            printf(" -> %.*s\n", (int)n, lnk); /* add if successfull */
        } else {
            putchar('\n'); /* dont if not */
        }

        pop_path_buffer(save);  /* cleanup */
    } else {
        putchar('\n'); /* if not link put newline now */
    }
}

/**
 * Print one file in column mode
 * @param finfo the file info to be printed
 */
static void list_file_column(struct FileInfo* finfo) {
    char* color;

    color = get_file_color(finfo);
    
    printf("%s%s%s\n",  /* print the data */
           flags.colored != NO ? color : "", finfo->name,  /* if not colored dont color */
           flags.colored != NO ? "\x1b[0m" : ""
    );
}

/** 
 * List a file normally (without -l or -1)
 * @param info the global folder information
 * @param finfo the file specific info
 * @param tty_width the width of the tty
 * @param index, the index in the direcory that has been printed
 * @param column_width the width of the column
 * @param row_count the count of rows
 */
static void list_file_normal(
    struct FileListInfo* info, 
    struct FileInfo* finfo, 
    int tty_width, 
    int index,
    int column_width,
    int row_count
) {
    char* color;

    color = get_file_color(finfo); /* get file color */
    
    if (info->total_len > tty_width) { /* snap to column if the files span multiple lines */
        if (index != 0 && index % row_count == 0) putchar('\n'); /* if at the end of the column put a new line */
        printf("%s%*s%s", flags.colored != NO ? color : "", -column_width, 
               finfo->name, flags.colored != NO ? "\x1b[0m" : ""); /* if not colored dont color */
    } else { /* otherwise just print next to eachother seperated by two spaces */
        printf("%s%s%s  ", flags.colored != NO ? color : "", finfo->name,
               flags.colored != NO ? "\x1b[0m" : "");
    }
}

/** 
 * Get the width of the tty, set to 0 if not a  tty
 * @param width the int pointer to store the width in
 */
static void get_window_size(int* width) {
    struct winsize w;
    ioctl(STDOUT_FILENO, TIOCGWINSZ, &w);
    if (!isatty(1)) {
        *width = 0;
    } else {
        *width = w.ws_col;
    }
}

/**
 * List a set of files
 * @param files a array of file info structs containing file data
 * @param file_len the amount of files
 * @param info the global folder infomation
 */
static void list_files(struct FileInfo* files, int file_len, struct FileListInfo info) {
   
    /* pre define variables to make gcc happy */
    int column_width = 0, row_count = 0, i = 0, width = 0;
    get_window_size(&width); /* get screen width */

    /* if your not a tty, set to column mode and disable color if not forced */
    if (width > 0) {
        column_width = info.max_name + 1;
        row_count = width / column_width;
    } else {
        flags.one_column = true;
        if (flags.colored == AUTO)
            flags.colored = NO;
    }

    /* if set to long list, display folder size */
    if (flags.more_info) {
        char total[13];
        print_file_size(info.total_size, total);
        printf("total %s\n", total);
    }

    /* list files base on list mode */
    for (i = 0; i < file_len; i++) {
        struct FileInfo finfo = files[i];
        if (flags.more_info) {              /* -l long list */
            list_file_long(&info, &finfo);
        } else if (flags.one_column) {      /* -1 column list */
            list_file_column(&finfo);
        } else {                            /* normal default listing */
            list_file_normal(&info, &finfo, width, i, column_width, row_count);
        }
        free(finfo.name); /* cleanup */
    }

    if (!flags.more_info) printf("\n"); /* only long long list prints a new line at the end */
}

/**
 * Get the number of places a number fills
 * @param n the number to check
 * @returns the num of places the number filles
 */
static int num_places (int n) {
    int r = 1;
    if (n < 0) n = (n == INT_MIN) ? INT_MAX: -n;
    while (n > 9) { /* keep going for each place */
        n /= 10;
        r++;
    }
    return r;
}

/**
 * Read and push a file info the given array
 * @param file a pointer to the list of files
 * @param info the global folder info to update as read
 * @param size the amount of files currently in the array
 * @param capacity the capacity of the array
 * @param file_path the path of the file
 */
static void push_file(
    struct FileInfo** files, 
    struct FileListInfo* info, 
    int* size, int* capacity, 
    const char* file_path 
) {
    /* allocate variables on the stack */
    struct FileInfo finfo;
    int user_len, group_len, name_len, size_len, link_len;

    /* if you fail to get the file info, abort */
    if (!get_file_info(file_path, &finfo)) return;

    /* if the array is full realloc to make it bigger */
    if (*size == *capacity) {
        *capacity *= 2;
        *files = xrealloc(*files, sizeof(struct FileInfo) * *capacity);
    }
    
    /* update user name length if its larger than global */
    user_len = strlen(finfo.usr->pw_name);
    if (user_len > info->max_usr) info->max_usr = user_len;

    /* update group name length if its larger than global */
    group_len = strlen(finfo.grp->gr_name);
    if (group_len > info->max_grp) info->max_grp = group_len;

    /* update file name length if its larger than global */
    name_len = strlen(file_path);
    if (name_len > info->max_name) info->max_name = name_len;

    /* update file size human readable length if its larger than global */
    size_len = strlen(finfo.size);
    if (size_len > info->max_size) info->max_size = size_len;

    /* update inode link place count length if its larger than global */
    link_len = num_places(finfo.links);
    if (link_len > info->max_link) info->max_link = link_len;

    /* update final info */
    info->total_len += name_len + 2;
    info->total_size += finfo.bytes;

    /* insert file data into array */
    (*files)[*size] = finfo;
    (*size)++; /* increment size counter */
}

/**
 * When recursing, read all files and folders, recurses each folder, and prints each file
 * @param dir_name the dir_name relative to the current path buffer
 */
static void recurse_directory(char* dir_name) {
    /* allocate variables on the stack */
    DIR* d;
    int capacity, size, save;
    struct dirent* file;
    struct FileInfo* files;
    struct FileListInfo info;

    /* push the dir name to the path buffer */
    save = push_path_buffer(dir_name);

    /* if failed to open dir abort */
    d = get_directory(get_path_buffer());
    if (d == NULL) {
        return;
    }

    /* allocate initial array*/
    capacity = 8;
    size = 0;
    
    files = xalloc(sizeof(struct FileInfo) * capacity);
    memset(&info, 0, sizeof(struct FileListInfo)); /* zero out default directory globals */

    /* for each file read, recurse if directory, read file if file */
    while((file = readdir(d)) != NULL) {
        if (!flags.hidden && prefix(".", file->d_name)) continue; /* if not set to show hidden, skip */
        if (flags.hide_dot && is_dot_dir(file->d_name)) continue; /* if its set to hide dot skip */
        if (file->d_type == DT_DIR && !is_dot_dir(file->d_name)) { /* dont recurse dot files or scary infinite loop */
            recurse_directory(file->d_name); /* recurse if directory */
        } else {
            push_file(&files, &info, &size, &capacity, file->d_name); /* read file if a file */
        }
    }
    
    /* print dir name */
    if (flags.colored == NO) {
        printf("\n%s:\n", get_path_buffer());
    } else {
        printf("\n%s%s:%s\n", DIR_COLOR, get_path_buffer(), FILE_COLOR);
    }

    /* list files */
    list_files(files, size, info);

    free(files); /* clean up */
    closedir(d);
    pop_path_buffer(save);
}

/** 
 * List directory non recursivly or recursivly
 * @param path the name of the directory to search
 */
static void list_directory(char* path) {

    /* allocate variables on the stack */
    DIR* d;
    int capacity, size, save;
    struct FileInfo* files;
    struct FileListInfo info;
    struct dirent* file;

    /* if set to recurse, run the recurse function */
    if (flags.recurse) {
        recurse_directory(path);
        return;
    }

    /* if failed to open directory, abort */
    d = get_directory(path);
    if (d == NULL) return;

    /* push folder to path buffer */
    save = push_path_buffer(path);

    /* set array defaults */
    capacity = 8;
    size = 0;

    /* allocate file array */ 
    files = xalloc(sizeof(struct FileInfo) * capacity);
    memset(&info, 0, sizeof(struct FileListInfo)); /* zero out directory globals */
    
    /* add each file regardless if its a directory or file since not recursing */
    while ((file = readdir(d)) != NULL) {
        if (!flags.hidden && prefix(".", file->d_name)) continue; /* if not set to show hidden ship */
        if (flags.hide_dot && is_dot_dir(file->d_name)) continue; /* if set to hide dot skip */
        push_file(&files, &info, &size, &capacity, file->d_name); /* add file to array */
    }

    /* only list files if there are any to list */
    if (size > 0) list_files(files, size, info);

    /* cleanup */
    free(files);
    closedir(d);
    pop_path_buffer(save);
}

/* return if a path is a directory */
static bool is_dir(const char* path) {
    struct stat s;
    if (stat(path, &s) < 0) return false;
    return S_ISDIR(s.st_mode);
}

/**
 * Goes though each argument and prints the argument if it is a file
 * @param start the argument to start at
 * @param argc the argument count
 * @param argv, the argument data
 */
static void list_file_args(int start, int argc, char** argv) {

    /* allocate variables on the stack */
    int capacity, size, i;
    struct FileInfo* files;
    struct FileListInfo info;

    /* array defaults */
    capacity = 8;
    size = 0;
    
    files = xalloc(sizeof(struct FileInfo) * capacity); /* allocate array */
    memset(&info, 0, sizeof(struct FileListInfo)); /* zero out globals */
    
    for (i = start; i < argc; i++) {
        if (is_dir(argv[i])) continue; /* if the argument is a dir skip */
        push_file(&files, &info, &size, &capacity, argv[i]);
    }
    
    /* print file args */
    if (size > 0) list_files(files, size, info);

    /* clean up */
    free(files);
}

/**
 * Prints help message for ls
 */
static void help(void) {
    printf("Usage: ls [FILE]...\n\n");
    printf("List directory contents\n\n");
    printf("\t-1\tOne column output\n");
    printf("\t-l\tLong format\n");
    printf("\t-o\tList raw octets instead of romanized file mode\n");
    printf("\t-a\tInclude names starting with .\n");
    printf("\t-A\tLike -a but without . and ..\n");
    printf("\t-R\tRecurse\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); /* next arg unused */
    switch (c) {
        case 'R':
            flags.recurse = true;
            break;
        case '1':
            flags.one_column = true;
            break;
        case 'A':
            flags.hide_dot = true;
            flags.hidden = true;
            break;
        case 'a':
            flags.hidden = true;
            break;
        case 'l':
            flags.more_info = true;
            break;
        case 'o':
            flags.octets = true;
            break;
        default:
            return ARG_INVALID;
    }
    return ARG_UNUSED;
}

/**
 * Takes in each long argument (--)
 * @param cur the current argument
 * @param next the next argument in argv that hasnt been parsed
 * @param if the next arg was used or if the arg was invalid
 */
static int long_arg(char* cur, char* next) {
    UNUSED(next); /* next arg unused */ 
    if (prefix("--color=", cur)) { /* parse --color argument */
        char* arg = cur + 8;
        if (streql("yes", arg) || streql("always", arg)) {
            flags.colored = YES;
        } else if (streql("auto", arg)) {
            flags.colored = AUTO;
        } else if (streql("no", arg) || streql("never", arg)) {
            flags.colored = NO;
        } else {
            error("invalid color options: %s", arg);
        }
    } else {
        return ARG_IGNORE; /* stop reading arguments */
    }
    return ARG_UNUSED; /* return */
}

/**
 * Lists a directorys contents 
 */
COMMAND(ls_main) {

    int start, i;
    bool titled;

    /* initalize flag defaults */
    flags.hidden = false;
    flags.more_info = false;
    flags.hide_dot = false;
    flags.one_column = false;
    flags.recurse = false;
    flags.colored = NO;
    flags.octets = false;

    /* parse given arguments */
    start = parse_args(argc, argv, help, short_arg, long_arg);
    
    /* if not arguments are given list current directory */
    if (argc - start == 0) {
        list_directory(".");
        return EXIT_SUCCESS;
    }

    /* list all arguments that are files */
    list_file_args(start, argc, argv); 

    /* list each directory in the arguments */
    titled = argc - start > 1;
    for (i = start; i < argc; i++) {

        if (!is_dir(argv[i])) continue; /* if not directory skip */
        
        if (titled && !flags.recurse) { /* list title of title is forced and not set to recurse*/
            if (flags.colored != NO) {
                printf("\n%s%s:%s\n", DIR_COLOR, argv[i], FILE_COLOR);
            } else {
                printf("\n%s:\n", argv[i]);
            }
        }

        list_directory(argv[i]); /* parse and list directory */
    }

    return EXIT_SUCCESS; /* return */
}