/*
 * Copyright (c) 2018 Richard Braun.
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 * Upstream site with license notes :
 * http://git.sceen.net/rbraun/librbraun.git/
 */

#ifndef KERN_SHELL_I_H
#define KERN_SHELL_I_H

#include <stddef.h>

#include <kern/macros.h>
#include <kern/mutex.h>

struct shell_cmd {
    struct shell_cmd *ht_next;
    struct shell_cmd *ls_next;
    const char *name;
    shell_fn_t fn;
    const char *usage;
    const char *short_desc;
    const char *long_desc;
};

struct shell_bucket {
    struct shell_cmd *cmd;
};

/*
 * Binary exponent and size of the hash table used to store commands.
 */
#define SHELL_HTABLE_BITS   6
#define SHELL_HTABLE_SIZE   (1 << SHELL_HTABLE_BITS)

/*
 * The command list is sorted.
 */
struct shell_cmd_set {
    struct mutex lock;
    struct shell_bucket htable[SHELL_HTABLE_SIZE];
    struct shell_cmd *cmd_list;
};

#define SHELL_LINE_MAX_SIZE 64

/*
 * Line containing a shell entry.
 *
 * The string must be nul-terminated. The size doesn't include this
 * additional nul character, the same way strlen() doesn't account for it.
 */
struct shell_line {
    char str[SHELL_LINE_MAX_SIZE];
    size_t size;
};

/*
 * Number of entries in the history.
 *
 * One of these entryes is used as the current line.
 */
#define SHELL_HISTORY_SIZE 21

#if SHELL_HISTORY_SIZE == 0
#error "shell history size must be non-zero"
#endif /* SHELL_HISTORY_SIZE == 0 */

/*
 * Shell history.
 *
 * The history is never empty. There is always at least one entry, the
 * current line, referenced by the newest (most recent) index. The array
 * is used like a circular buffer, i.e. old entries are implicitely
 * erased by new ones. The index references the entry used as a template
 * for the current line.
 */
struct shell_history {
    struct shell_line lines[SHELL_HISTORY_SIZE];
    size_t newest;
    size_t oldest;
    size_t index;
};

/*
 * This value changes depending on the standard used and was chosen arbitrarily.
 */
#define SHELL_ESC_SEQ_MAX_SIZE 8

#define SHELL_MAX_ARGS 16

/*
 * Shell structure.
 *
 * A shell instance can include temporary variables to minimize stack usage.
 */
struct shell {
    struct shell_cmd_set *cmd_set;

    shell_getc_fn_t getc_fn;
    shell_vfprintf_fn_t vfprintf_fn;
    void *io_object;

    struct shell_history history;

    /* Cursor within the current line */
    size_t cursor;

    /* Members used for escape sequence parsing */
    char esc_seq[SHELL_ESC_SEQ_MAX_SIZE];
    size_t esc_seq_index;

    /*
     * Buffer used to store the current line during argument processing.
     *
     * The pointers in the argv array point inside this buffer. The
     * separators immediately following the arguments are replaced with
     * null characters.
     */
    char tmp_line[SHELL_LINE_MAX_SIZE];

    int argc;
    char *argv[SHELL_MAX_ARGS];
};

#endif /* KERN_SHELL_I_H */