#include "teensy_ui.h"

#include <assert.h>
#include <math.h>
#include <stdarg.h>
#include <string.h>
 
#include "teensy_list.h"

#define TEXT_HEIGHT (8)
#define MAX_LAYOUTS (16)
#define MAX_WINDOWS (255)

#define window() (uictx.active)
#define layout() (window()->layout - 1)
#define push_layout() (window()->layout++)
#define pop_layout() (--window()->layout)
#define padding() (uictx.style.padding)
#define control_padding() (uictx.style.control_padding)
#define title_bar_height() (uictx.style.title_bar_height)

enum {
    CMD_RECT,
    CMD_TEXT,
    CMD_CLIP,
    CMD_IMAGE,
};
typedef uint8_t Cmd_Kind;

typedef struct {
    const char *text;
    ty_Recti rect;
    ty_Color color;
    ty_Image img;
    Cmd_Kind kind;
    tyui_Align align;
} Cmd;

typedef struct {
    int idx;
    int columns;
    float column_widths[TYUI_MAX_LAYOUT_SIZE];
    int max_height;
    int total_height;
    int x;
    int width;
} Layout;

typedef struct {
    Cmd *cmds;
    Layout *layout;
    Layout layout_stack[MAX_LAYOUTS];
    ty_Recti rect;
    uint32_t flags;
    bool focused;
    bool lmb_down;
    bool rmb_down;
    bool lmb_pressed;
    bool rmb_pressed;
} Window;

typedef struct {
    Window *active;
    Window root;
    Window windows[MAX_WINDOWS];
    int window_order[MAX_WINDOWS];
    int window_count;
    int layout_idx;
    int layout_size;
    tyui_Style style;
    const ty_Font *font;
    const float *layout;

    ty_Vec2i prev_mouse_pos;
} Ctx;

static
tyui_Style default_style = {
    .fg_normal        = ty_color(200, 200, 200),
    .bg_normal        = ty_color(20, 20, 20),
    .fg_hover         = ty_color(255, 255, 255),
    .bg_hover         = ty_color(100, 100, 100),
    .fg_pressed       = ty_color(150, 150, 150),
    .bg_pressed       = ty_color(10, 10, 10),
    .win_bg           = ty_color(48, 48, 48),
    .win_border       = ty_color(24, 24, 24),
    .win_title        = ty_color(64, 128, 128),
    .frame            = ty_color(10, 10, 10),
    .title_bar_height = 12,
    .padding          = 1,
    .control_padding  = 2,
    .frame_size       = 1,
    .grabber_size     = 4,
    .slider_fmt       = "%2d"
};

static
Ctx uictx;

static
void rect_cmd(ty_Recti rect, ty_Color color)
{
    Cmd cmd = {};
    cmd.kind = CMD_RECT;
    cmd.rect = rect;
    cmd.color = color;

    ty_list_append(window()->cmds, cmd);
}

static
void text_cmd(const char *text, ty_Recti rect, tyui_Align align)
{
    Cmd cmd = {};
    cmd.kind = CMD_TEXT;
    cmd.text = text;
    cmd.rect = rect;
    cmd.align = align;

    ty_list_append(window()->cmds, cmd);
}

static
void image_cmd(ty_Image img, ty_Recti rect)
{
    Cmd cmd = {};
    cmd.kind = CMD_IMAGE;
    cmd.img = img;
    cmd.rect = rect;
    ty_list_append(window()->cmds, cmd);
}

static
void clip_cmd(ty_Recti rect)
{
    Cmd cmd = {};
    cmd.kind = CMD_CLIP;

    if (rect.w < 0 || rect.h < 0)
        rect = window()->rect; // This is a full screen clip

    cmd.rect = ty_recti_clamp(rect, window()->rect);
    ty_list_append(window()->cmds, cmd);
}

static
void draw_frame(ty_Recti rect, ty_Color bg_col)
{
    clip_cmd(TY_CLIP_NONE);
    rect_cmd(rect, uictx.style.frame);
    ty_Recti content_rect = ty_recti_shrink(rect, uictx.style.frame_size);
    rect_cmd(content_rect, bg_col);
    clip_cmd(content_rect);
}

static
void advance_layout(void)
{
    Layout *l = layout();

    if (++l->idx < l->columns)
        return;

    l->total_height += l->max_height + padding();
    l->idx = 0;
    l->max_height = 0;

    if (l == window()->layout_stack)
        l->x = padding();
    else
        l->x = 0;
}

static
int get_column_width(const Layout *l)
{
    float width = l->column_widths[l->idx];
    if (width < 0)
        return width + l->width - l->x + 1;
    if (width < 1)
        return (l->width - padding() * 2) * width;
    return width;
}

static
ty_Recti next_rect(int height)
{
    Layout *l = layout();

    l->max_height = ty_max(l->max_height, height);

    float width = get_column_width(l);

    int x = 0;
    int y = 0;
    for (Layout *outer = window()->layout_stack; outer <= l; outer++) {
        x += outer->x;
        y += outer->total_height;
    }

    x += window()->rect.x;
    y += window()->rect.y;

    width = ty_max(width, 0);
    height = ty_max(height, 0);

    l->x += width + padding();

    advance_layout();

    return ty_recti(x, y, width, height);
}

static
ty_Vec2i mouse_delta(void)
{
    ty_Vec2i cur = ty_mouse_pos();
    return ty_vec2i(
        cur.x - uictx.prev_mouse_pos.x,
        cur.y - uictx.prev_mouse_pos.y
    );
}

static
bool is_hovered(ty_Recti rect)
{
    return ty_pointi_in_recti(ty_mouse_pos(), rect);
}

static
Window create_window(ty_Recti rect, uint32_t flags)
{
    Window win = {};
    win.rect = rect;
    win.flags = flags;
    win.cmds = ty_list_create();
    ty_list_reserve(win.cmds, 64);
    return win;
}

void tyui_init(const ty_Font *font)
{
    assert(font);

    uint32_t root_flags = 0;
    root_flags |= TYUI_WIN_NORESIZE;
    root_flags |= TYUI_WIN_NOCLOSE;
    root_flags |= TYUI_WIN_NOMOVE;
    root_flags |= TYUI_WIN_INVISIBLE;

    uictx.root = create_window(ty_recti(0, 0, 256, 256), root_flags);

    uictx.style = default_style;
    uictx.font = font;

    uictx.active = &uictx.root;
}

void tyui_deinit(void)
{
    for (int i = 0; i < uictx.window_count; i++)
        ty_list_free(uictx.windows[i].cmds);
}

void tyui_push_layout(const float *column_widths)
{
    assert(column_widths);

    Layout *outer = layout();

    Layout *new = push_layout();
    memset(new, 0, sizeof(*new));

    for (const float *width = column_widths; *width != 0; width++)
        new->columns++;

    memcpy(
        new->column_widths,
        column_widths,
        sizeof(*column_widths) * new->columns
    );

    new->x = 0;

    if (new != window()->layout_stack)
        new->width = get_column_width(outer);
    else
        new->width = window()->rect.w;

    new->width -= padding();
}

void tyui_pop_layout(void)
{
    Layout *old = pop_layout();
    Layout *top = layout();
    top->max_height = ty_max(top->max_height, old->total_height - padding());
    top->x += old->width + padding();
    advance_layout();
}

bool tyui_begin_window_ex(tyui_Window_Conf conf, bool *closed_ptr)
{
    assert(conf.title);
    assert(conf.id);

    bool closed = false;

    if (closed_ptr)
        closed = *closed_ptr;

    if (window() != &uictx.root) {
        ty_log_err("cannot create window within another window");
        return false;
    }

    if (closed)
        return !closed;

    if (*conf.id == 0) {
        *conf.id = ++uictx.window_count;
        uictx.windows[*conf.id - 1] = create_window(conf.rect, conf.flags);
        uictx.window_order[uictx.window_count - 1] = *conf.id;
    }

    Window *win = &uictx.windows[*conf.id - 1];
    uictx.active = win;
    win->layout = win->layout_stack;

    if (win->flags & TYUI_WIN_INVISIBLE)
        goto done;

    ty_Vec2i mouse_pos = ty_mouse_pos();
    ty_Vec2i md = mouse_delta();
    mouse_pos.x -= md.x;
    mouse_pos.y -= md.y;

    bool hovering_resizer = false;

    // Grabbing resizer?
    {
        ty_Vec2i win_end = ty_recti_end(win->rect);
        ty_Recti resize_rect = ty_recti(
            win_end.x - 20, win_end.y - 20 + TEXT_HEIGHT,
            20, 20
        );

        hovering_resizer =
            ty_pointi_in_recti(mouse_pos, resize_rect) ||
            ty_pointi_in_recti(ty_mouse_pos(), resize_rect);

        if (win->lmb_down && hovering_resizer) {
            win->rect.w += md.x;
            win->rect.h += md.y;

            win->rect.w = ty_max(win->rect.w, conf.min_size.x);
            win->rect.h = ty_max(win->rect.h, conf.min_size.y);
        }
    }

    ty_Recti title_rect = win->rect;
    title_rect.h = title_bar_height();

    // Grabbing title bar?
    {
        if (
            win->lmb_down && 
            (ty_pointi_in_recti(mouse_pos, title_rect) ||
            ty_pointi_in_recti(ty_mouse_pos(), title_rect))
        ) {
            win->rect.x += md.x;
            win->rect.y += md.y;

            title_rect = win->rect;
            title_rect.h = title_bar_height();
        }
    }

    clip_cmd(TY_CLIP_NONE);

    rect_cmd(title_rect, uictx.style.win_title);
    text_cmd(conf.title, ty_recti_shrink(title_rect, 1), TYUI_ALIGN_LEFT);

    ty_Recti body_rect = win->rect;
    body_rect.y += title_bar_height();
    body_rect.h -= title_bar_height();
    rect_cmd(body_rect, uictx.style.win_border);
    rect_cmd(ty_recti_shrink(body_rect, 1), uictx.style.win_bg);

    if (hovering_resizer) {
        ty_Recti right_bar = ty_recti(
            win->rect.x + win->rect.w - 1, 0,
            1, win->rect.y + win->rect.h
        );
        rect_cmd(right_bar, uictx.style.win_title);
        ty_Recti bot_bar = ty_recti(
            0, win->rect.y + win->rect.h - 1,
            win->rect.x + win->rect.w, 1
        );
        rect_cmd(bot_bar, uictx.style.win_title);
    }

    tyui_push_layout((float[]){-1, 0});
    layout()->total_height = title_bar_height() + padding();

done:
    return !closed;
}

void tyui_end_window(void)
{
    if (window() == &uictx.root) {
        ty_log_err("ending window with no window open");
        return;
    }

    clip_cmd(TY_CLIP_NONE);

    uictx.active = &uictx.root;
}

void tyui_text_ex(tyui_Align align, const char *fmt, ...)
{
    va_list args;
    va_start(args, fmt);
    char *text = ty_format_args(fmt, args);
    va_end(args);

    ty_Recti rect = next_rect(TEXT_HEIGHT);

    clip_cmd(rect);
    text_cmd(text, rect, align);
}

bool tyui_button(const char *text)
{
    ty_Recti rect = next_rect(TEXT_HEIGHT + control_padding() * 2);
    ty_Color bg_col = uictx.style.bg_normal;

    bool clicked = false;
    if (is_hovered(rect)) {
        clicked = window()->lmb_pressed;
        bg_col = window()->lmb_down
            ? uictx.style.bg_pressed
            : uictx.style.bg_hover;
    }

    draw_frame(rect, bg_col);
    text_cmd(text, ty_recti_shrink(rect, control_padding()), TYUI_ALIGN_CENTER);

    return clicked;
}

void tyui_slider_ex(
    float min,
    float max,
    float *value_ptr,
    bool show_value,
    tyui_Align value_align
) {
    assert(value_ptr);

    const int grabber_size = uictx.style.grabber_size;

    ty_Recti rect = next_rect(TEXT_HEIGHT + control_padding() * 2);
    ty_Color bg_col = uictx.style.bg_normal;
    ty_Color fg_col = uictx.style.fg_normal;

    bool clicked = false;
    if (is_hovered(rect)) {
        clicked = window()->lmb_down;
        if (window()->lmb_down) {
            bg_col = uictx.style.bg_pressed;
            fg_col = uictx.style.fg_pressed;
        } else {
            bg_col = uictx.style.bg_hover;
            fg_col = uictx.style.fg_hover;
        }
    }

    if (clicked) {
        ty_Vec2i mp = ty_mouse_pos();
        float x = mp.x - rect.x;
        float p = x / (rect.w - 1);
        *value_ptr = ty_clamp(p * (max - min) + min, min, max);
    }

    float value = *value_ptr;

    draw_frame(rect, bg_col);
    if (show_value) {
        text_cmd(
            ty_format(uictx.style.slider_fmt, (int)round(value)),
            ty_recti_shrink(rect, control_padding()),
            value_align
        );
    }

    // Grabber
    {
        float p = (value - min) / max;
        int x = (rect.w - grabber_size) * p + rect.x;

        ty_Recti grabber_rect = ty_recti(
            x, rect.y,
            grabber_size, rect.h
        );

        draw_frame(grabber_rect, fg_col);
    }
}

static
void draw_window(Window *win)
{
    for (size_t i = 0; i < ty_list_len(win->cmds); i++) {
        Cmd cmd = win->cmds[i];
        switch (cmd.kind) {
        case CMD_RECT:
            ty_draw_rect(cmd.rect, cmd.color);
            break;
        case CMD_TEXT: {
            int text_width = ty_font_width(uictx.font, cmd.text);
            ty_Vec2i pos = ty_recti_start(cmd.rect);
            switch (cmd.align) {
            case TYUI_ALIGN_LEFT:
                break;
            case TYUI_ALIGN_RIGHT:
                pos.x += cmd.rect.w - text_width;
                break;
            case TYUI_ALIGN_CENTER:
                pos.x += (cmd.rect.w - text_width) / 2;
                break;
            }
            pos.y += (cmd.rect.h - ty_font_height(uictx.font)) / 2;
            ty_draw_text(uictx.font, pos, cmd.text);
            break;
        }
        case CMD_IMAGE:
            ty_draw_image(cmd.img, ty_recti_start(cmd.rect));
            break;
        case CMD_CLIP:
            ty_draw_set_clip(cmd.rect);
            break;
        }
    }
    ty_draw_set_clip(TY_CLIP_NONE);
    ty_list_clear(win->cmds);
}

static
void focus_window(tyui_Id win_id)
{
    int idx = uictx.window_count - 1;
    for (; idx >= 0; idx--) {
        if (uictx.window_order[idx] == win_id)
            break;
    }

    if (idx < 0)
        ty_log_err("uh oh");

    for (int i = idx; i < uictx.window_count - 1; i++)
        uictx.window_order[i] = uictx.window_order[i + 1];
    uictx.window_order[uictx.window_count - 1] = win_id;

    uictx.windows[win_id - 1].focused = true;
}

static
void update_windows(void)
{
    for (int i = 0; i < uictx.window_count; i++) {
        Window *win = &uictx.windows[i];
        win->lmb_down = false;
        win->rmb_down = false;
        win->lmb_pressed = false;
        win->rmb_pressed = false;
        win->focused = false;
    }

    for (int i = uictx.window_count - 1; i >= 0; i--) {
        tyui_Id win_id = uictx.window_order[i];
        Window *win = &uictx.windows[win_id - 1];
        if (!is_hovered(win->rect))
            continue;

        win->lmb_down    = ty_button_down(TY_BTN_DB_LMB);
        win->rmb_down    = ty_button_down(TY_BTN_DB_RMB);
        win->lmb_pressed = ty_button_pressed(TY_BTN_DB_LMB);
        win->rmb_pressed = ty_button_pressed(TY_BTN_DB_RMB);

        if (win->lmb_down || win->rmb_down)
            focus_window(win_id);

        break;
    }
}

void tyui_draw(void)
{
    draw_window(&uictx.root);

    for (int i = 0; i < uictx.window_count; i++) {
        tyui_Id win_id = uictx.window_order[i];
        draw_window(&uictx.windows[win_id - 1]);
    }

    uictx.prev_mouse_pos = ty_mouse_pos();
    update_windows();
}