typedef struct caret_t caret_t;
struct caret_t {
    i64 ifront;
    union {
        r1i64_t range;
        i64 pos[2];
    };
};

typedef struct xy_t xy_t;
struct xy_t {
    i64 col;
    i64 line;
};

typedef struct edit16_t edit16_t;
struct edit16_t {
    r1i64_t range;
    s16_t string;
};

// @todo: redo tree
typedef array(edit16_t) array_edit16_t;
typedef array(caret_t) array_caret_t;
typedef struct history16_t history16_t;
struct history16_t {
    array_edit16_t edits;
    array_caret_t carets;
};

typedef array(history16_t) array_history16_t;
typedef struct buffer16_id_t buffer16_id_t;
struct buffer16_id_t { i64 e; };

typedef struct buffer16_t buffer16_t;
struct buffer16_t {
    s8_t name;
    buffer16_id_t id;

    i32 change_id;
    i8 edit_phase;

    struct {
        b8 dirty: 1;
        b8 history: 1;
        b8 line_starts: 1;
    } flags;

    union {
        s16_t string;
        u16 *data;
        struct {
            u16 *str;
            i64  len;
        };
    };
    i64 cap;
    array_i64_t line_starts;

    array_history16_t undo_stack;
    array_history16_t redo_stack;
    alo_t alo;
};

const b32 dont_kill_selection = false;
const b32 kill_selection = true;


///////////////////////////////
// caret helpers
fn caret_t        caret_make(i64 front, i64 back);
fn i64            caret_get_front(caret_t caret);
fn i64            caret_get_back(caret_t caret);
fn caret_t        caret_set_front(caret_t caret, i64 pos);
fn caret_t        caret_set_back(caret_t caret, i64 pos);
fn b32            carets_are_equal(caret_t a, caret_t b);
fn b32            carets_overlap(caret_t a, caret_t b);

///////////////////////////////
// buffer helpers
fn i64            buffer16_pos_to_line(buffer16_t *buffer, i64 pos);
fn r1i64_t        buffer16_get_line_range(buffer16_t *buffer, i64 line);
fn r1i64_t        buffer16_get_line_range_full(buffer16_t *buffer, i64 line, i64 *eof);
fn xy_t           buffer16_pos_to_xy(buffer16_t *buffer, i64 pos);
fn i64            buffer16_xy_to_pos(buffer16_t *buffer, xy_t xy);
fn i64            buffer16_xy_to_pos_without_new_line(buffer16_t *buffer, xy_t xy);
fn s16_t          buffer16_get_string(buffer16_t *buffer, r1i64_t range);
fn s16_t          buffer16_get_line_string(buffer16_t *buffer, i64 line);
fn r1i64_t        buffer16_get_range_end(buffer16_t *buffer);
fn r1i64_t        buffer16_get_range(buffer16_t *buffer);
fn i64            buffer16_clamp_pos(buffer16_t *buffer, i64 pos);
fn r1i64_t        buffer16_clamp_range(buffer16_t *buffer, r1i64_t range);
fn i64            buffer16_get_word_start(buffer16_t *buffer, i64 pos);
fn i64            buffer16_get_word_end(buffer16_t *buffer, i64 pos);
fn i64            buffer16_get_next_word_end(buffer16_t *buffer, i64 pos);
fn i64            buffer16_get_prev_word_start(buffer16_t *buffer, i64 pos);
fn i64            buffer16_get_line_start(buffer16_t *buffer, i64 pos, i64 *eof);
fn i64            buffer16_get_line_end(buffer16_t *buffer, i64 pos, i64 *eof);
fn i64            buffer16_get_line_start_full(buffer16_t *buffer, i64 pos);
fn i64            buffer16_get_line_end_full(buffer16_t *buffer, i64 pos);
fn r1i64_t        buffer16_enclose_word(buffer16_t *buffer, i64 pos);
fn u16            buffer16_get_char(buffer16_t *buffer, i64 pos);
fn i64            buffer16_offset_pos_by_line(buffer16_t *buffer, i64 pos, i64 line_offset);

///////////////////////////////
// buffer raw textural operations. no history
fn void           buffer16_raw_grow(buffer16_t *buffer, i64 change_size);
fn void           buffer16_raw_replace_text(buffer16_t *buffer, r1i64_t range, s16_t string);

///////////////////////////////
// buffer multicursor + history
fn void           buffer16_init(alo_t alo, buffer16_t *buffer, s8_t name, i64 size);
fn void           buffer16_deinit(buffer16_t *buffer);
fn void           buffer16_add_edit(array_edit16_t *edits, r1i64_t range, s16_t string);
fn array_edit16_t buffer16_begin_edit(alo_t alo, buffer16_t *buffer, array_caret_t *carets);
fn void           buffer16_end_edit(buffer16_t *buffer, array_edit16_t *edits, array_caret_t *carets, b32 kill_selection);
fn void           buffer16_merge_carets(buffer16_t *buffer, array_caret_t *carets);
fn void           buffer16_adjust_carets(array_edit16_t *edits, array_caret_t *carets);

fn void           buffer16_redo_edit(buffer16_t *buffer, array_caret_t *carets);
fn void           buffer16_undo_edit(buffer16_t *buffer, array_caret_t *carets);

fn void           buffer16_save_history_before_merge_cursor(buffer16_t *buffer, array_history16_t *stack, array_caret_t *carets);
fn void           buffer16_save_history_before_apply_edits(buffer16_t *buffer, array_history16_t *stack, array_edit16_t *edits);
fn void           buffer16_pre_begin_edit_save_caret_history(buffer16_t *buffer, array_caret_t *carets);

fn void           buffer16_dealloc_history_entries(buffer16_t *buffer, array_history16_t *entries);
fn void           buffer16_dealloc_history_array(buffer16_t *buffer, array_history16_t *entries);
fn void           buffer16_multi_cursor_apply_edits(buffer16_t *buffer, array_edit16_t edits);