/*
 * wl_client_side_decorations.c
 * Copyright (C) 2021 Kovid Goyal <kovid at kovidgoyal.net>
 *
 * Distributed under terms of the GPL3 license.
 */

#include "wl_client_side_decorations.h"

#include "backend_utils.h"
#include <sys/mman.h>
#include <errno.h>
#include <string.h>
#include <stdlib.h>

#define debug(...) if (_glfw.hints.init.debugRendering) fprintf(stderr, __VA_ARGS__);
#define decs window->wl.decorations

#define ARGB(a, r, g, b) (((a) << 24) | ((r) << 16) | ((g) << 8) | (b))
#define A(x) (((x) >> 24) & 0xff)
#define R(x) (((x) >> 16) & 0xff)
#define G(x) (((x) >> 8) & 0xff)
#define B(x) ((x) & 0xff)
#define SWAP(x, y) do { __typeof__(x) SWAP = x; x = y; y = SWAP; } while (0)

static const uint32_t passive_bg_color = 0xffeeeeee;
static const uint32_t active_bg_color = 0xffdddad6;
typedef float kernel_type;

static void
build_blur_kernel(kernel_type *blur_kernel, const size_t size, kernel_type sigma) {
    // 1D Normalized Gaussian
    const kernel_type half = size / (kernel_type)2;
	kernel_type sum = 0;
	for (size_t i = 0; i < size; i++) {
		kernel_type f = (i - half);
		blur_kernel[i] = (kernel_type)exp(- f * f / sigma);
		sum += blur_kernel[i];
	}
	for (size_t i = 0; i < size; i++) blur_kernel[i] /= sum;
}

static void
blur_mask(kernel_type *image_data, ssize_t width, ssize_t height, ssize_t kernel_size, kernel_type sigma, kernel_type *scratch, kernel_type *blur_kernel, ssize_t margin) {
    (void)margin;
    build_blur_kernel(blur_kernel, kernel_size, sigma);
    const size_t half = kernel_size / 2;

    for (ssize_t y = 0; y < height; y++) {
        kernel_type *s = image_data + y * width, *d = scratch + y * width;
        for (ssize_t x = 0; x < width; x++) {
            kernel_type a = 0;
            for (ssize_t k = 0; k < kernel_size; k++) {
                const ssize_t px = x + k - half;
                if (0 <= px && px < width) a += s[px] * blur_kernel[k];
            }
            d[x] = a;
        }
    }

    for (ssize_t y = 0; y < height; y++) {
        kernel_type *d = image_data + y * width;
        for (ssize_t x = 0; x < width; x++) {
            kernel_type a = 0;
            for (ssize_t k = 0; k < kernel_size; k++) {
                const ssize_t py = y + k - half;
                if (0 <= py && py < height) {
                    kernel_type *s = scratch + py * width;
                    a += s[x] * blur_kernel[k];
                }
            }
            d[x] = a;
        }
    }
}

static kernel_type*
create_shadow_mask(size_t width, size_t height, size_t margin, size_t kernel_size, kernel_type base_alpha, kernel_type sigma) {
    kernel_type *mask = calloc(sizeof(kernel_type), 2 * width * height + kernel_size);
    if (!mask) return NULL;
    for (size_t y = margin; y < height - margin; y++) {
        kernel_type *row = mask + y * width;
        for (size_t x = margin; x < width - margin; x++) row[x] = base_alpha;
    }
    blur_mask(mask, width, height, kernel_size, sigma, mask + width * height, (kernel_type*)(mask + 2 * width * height), margin);
    return mask;
}

static void
swap_buffers(_GLFWWaylandBufferPair *pair) {
    SWAP(pair->front, pair->back);
    SWAP(pair->data.front, pair->data.back);
}

static size_t
init_buffer_pair(_GLFWWaylandBufferPair *pair, size_t width, size_t height, unsigned scale) {
    memset(pair, 0, sizeof(_GLFWWaylandBufferPair));
    pair->width = width * scale;
    pair->height = height * scale;
    pair->stride = 4 * pair->width;
    pair->size_in_bytes = pair->stride * pair->height;
    return 2 * pair->size_in_bytes;
}

static void
alloc_buffer_pair(_GLFWWaylandBufferPair *pair, struct wl_shm_pool *pool, uint8_t *data, size_t *offset) {
    pair->data.a = data + *offset;
    pair->a = wl_shm_pool_create_buffer(pool, *offset, pair->width, pair->height, pair->stride, WL_SHM_FORMAT_ARGB8888);
    *offset += pair->size_in_bytes;
    pair->data.b = data + *offset;
    pair->b = wl_shm_pool_create_buffer(pool, *offset, pair->width, pair->height, pair->stride, WL_SHM_FORMAT_ARGB8888);
    *offset += pair->size_in_bytes;
    pair->front = pair->a; pair->back = pair->b;
    pair->data.front = pair->data.a; pair->data.back = pair->data.b;
}

#define st decs.shadow_tile

void
initialize_csd_metrics(_GLFWwindow *window) {
    decs.metrics.width = 12;
    decs.metrics.top = 36;
    decs.metrics.visible_titlebar_height = window->wl.decorations.metrics.top - window->wl.decorations.metrics.width;
    decs.metrics.horizontal = 2 * window->wl.decorations.metrics.width;
    decs.metrics.vertical = window->wl.decorations.metrics.width + window->wl.decorations.metrics.top;
}

static size_t
create_shadow_tile(_GLFWwindow *window) {
    const size_t margin = decs.bottom.buffer.height;
    if (st.data && st.for_decoration_size == margin) return margin;
    st.for_decoration_size = margin;
    free(st.data);
    st.segments = 7;
    st.stride = st.segments * margin;
    st.corner_size = margin * (st.segments - 1) / 2;
    kernel_type* mask = create_shadow_mask(st.stride, st.stride, margin, 2 * margin + 1, (kernel_type)0.7, 32 * margin);
    st.data = malloc(sizeof(uint32_t) * st.stride * st.stride);
    if (st.data) for (size_t i = 0; i < st.stride * st.stride; i++) st.data[i] = ((uint8_t)(mask[i] * 255)) << 24;
    free(mask);
    return margin;
}


static void
render_title_bar(_GLFWwindow *window, bool to_front_buffer) {
    const bool is_focused = window->id == _glfw.focusedWindowId;
    uint32_t bg_color = is_focused ? active_bg_color : passive_bg_color;
    uint8_t *output = to_front_buffer ? decs.top.buffer.data.front : decs.top.buffer.data.back;

    // render shadow part
    const size_t margin = create_shadow_tile(window);
    const size_t edge_segment_size = st.corner_size - margin;
    const uint8_t divisor = is_focused ? 1 : 2;
    for (size_t y = 0; y < margin; y++) {
        // left segment
        uint32_t *s = st.data + y * st.stride + margin;
        uint32_t *d = (uint32_t*)(output + y * decs.top.buffer.stride);
        for (size_t x = 0; x < edge_segment_size; x++) d[x] = (A(s[x]) / divisor) << 24;
        // middle segment
        s += edge_segment_size;
        size_t limit = decs.top.buffer.width > edge_segment_size ? decs.top.buffer.width - edge_segment_size : 0;
        for (size_t x = edge_segment_size, sx = 0; x < limit; x++, sx = (sx + 1) % margin) d[x] = (A(s[sx]) / divisor) << 24;
        // right segment
        s += margin;
        for (size_t x = limit; x < decs.top.buffer.width; x++, s++) d[x] = (A(*s) / divisor) << 24;
    }

    // render text part
    output += decs.top.buffer.stride * margin;
    if (window->wl.title && window->wl.title[0] && _glfw.callbacks.draw_text) {
        uint32_t fg_color = is_focused ? 0xff444444 : 0xff888888;
        if (_glfw.callbacks.draw_text((GLFWwindow*)window, window->wl.title, fg_color, bg_color, output, decs.top.buffer.width, decs.top.buffer.height - margin, 0, 0, 0)) return;
    }
    for (uint32_t *px = (uint32_t*)output, *end = (uint32_t*)(output + decs.top.buffer.size_in_bytes); px < end; px++) {
        *px = bg_color;
    }
}

static void
update_title_bar(_GLFWwindow *window) {
    render_title_bar(window, false);
    swap_buffers(&decs.top.buffer);
}

static void
render_edges(_GLFWwindow *window) {
    const size_t margin = create_shadow_tile(window);
    if (!st.data) return;  // out of memory

    // bottom edge
    uint32_t *src = st.data + (st.segments - 1) * margin * st.stride;
    for (size_t y = 0; y < margin; y++) {
        uint32_t *d = (uint32_t*)(decs.bottom.buffer.data.front + y * decs.bottom.buffer.stride);
        uint32_t *s = src + st.stride * y;
        // left corner
        for (size_t x = 0; x < st.corner_size && x < decs.bottom.buffer.width; x++) d[x] = s[x];
        // middle
        size_t pos = st.corner_size, limit = decs.bottom.buffer.width > st.corner_size ? decs.bottom.buffer.width - st.corner_size : 0;
        s += st.corner_size;
        while (pos < limit) {
            uint32_t *p = d + pos;
            for (size_t x = 0; x < margin && pos + x < limit; x++) p[x] = s[x];
            pos += margin;
        }
        // right corner
        s += margin;
        for (size_t x = 0; x < st.corner_size && limit + x < decs.bottom.buffer.width; x++) d[limit + x] = s[x];
    }

    // upper corners
    for (size_t y = 0; y < st.corner_size && y < decs.left.buffer.height; y++) {
        uint32_t *left_src = st.data + st.stride * y;
        uint32_t *left_dest = (uint32_t*)(decs.left.buffer.data.front + y * decs.left.buffer.stride);
        memcpy(left_dest, left_src, margin * sizeof(uint32_t));
        uint32_t *right_src = left_src + 2 * st.corner_size;
        uint32_t *right_dest = (uint32_t*)(decs.right.buffer.data.front + y * decs.right.buffer.stride);
        memcpy(right_dest, right_src, margin * sizeof(uint32_t));
    }

    // lower corners
    size_t src_height = st.corner_size - margin;
    size_t dest_top = decs.left.buffer.height > src_height ? decs.left.buffer.height - src_height : 0;
    size_t src_top = st.corner_size + margin;
    for (size_t src_y = src_top, dest_y = dest_top; src_y < src_top + src_height && dest_y < decs.left.buffer.height; src_y++, dest_y++) {
        uint32_t *s = st.data + st.stride * src_y;
        uint32_t *d = (uint32_t*)(decs.left.buffer.data.front + dest_y * decs.left.buffer.stride);
        memcpy(d, s, margin * sizeof(uint32_t));
        s += 2 * st.corner_size;
        d = (uint32_t*)(decs.right.buffer.data.front + dest_y * decs.left.buffer.stride);
        memcpy(d, s, margin * sizeof(uint32_t));
    }

    // sides
    size_t limit = decs.left.buffer.height > src_height ? decs.left.buffer.height - src_height : 0;
    for (size_t dest_y = st.corner_size, src_y = 0; dest_y < limit; dest_y++, src_y = (src_y + 1) % margin) {
        uint32_t *src = st.data + (st.corner_size + src_y) * st.stride;
        uint32_t *left_dest = (uint32_t*)(decs.left.buffer.data.front + dest_y * decs.left.buffer.stride);
        memcpy(left_dest, src, margin * sizeof(uint32_t));
        src += 2 * st.corner_size;
        uint32_t *right_dest = (uint32_t*)(decs.right.buffer.data.front + dest_y * decs.right.buffer.stride);
        memcpy(right_dest, src, margin * sizeof(uint32_t));
    }

#define copy(which) for (uint32_t *src = (uint32_t*)decs.which.buffer.data.front, *dest = (uint32_t*)decs.which.buffer.data.back; src < (uint32_t*)(decs.which.buffer.data.front + decs.which.buffer.size_in_bytes); src++, dest++) *dest = (A(*src) / 2 ) << 24;
    copy(left); copy(bottom); copy(right);
#undef copy

}
#undef st

static bool
create_shm_buffers(_GLFWwindow* window) {
    const unsigned scale = window->wl.scale >= 1 ? window->wl.scale : 1;

    const size_t vertical_width = decs.metrics.width, vertical_height = window->wl.height + decs.metrics.top;
    const size_t horizontal_height = decs.metrics.width, horizontal_width = window->wl.width + 2 * decs.metrics.width;

    decs.mapping.size = 0;
    decs.mapping.size += init_buffer_pair(&decs.top.buffer, window->wl.width, decs.metrics.top, scale);
    decs.mapping.size += init_buffer_pair(&decs.left.buffer, vertical_width, vertical_height, scale);
    decs.mapping.size += init_buffer_pair(&decs.bottom.buffer, horizontal_width, horizontal_height, scale);
    decs.mapping.size += init_buffer_pair(&decs.right.buffer, vertical_width, vertical_height, scale);

    int fd = createAnonymousFile(decs.mapping.size);
    if (fd < 0) {
        _glfwInputError(GLFW_PLATFORM_ERROR, "Wayland: Creating a buffer file for %zu B failed: %s",
                        decs.mapping.size, strerror(errno));
        return false;
    }
    decs.mapping.data = mmap(NULL, decs.mapping.size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
    if (decs.mapping.data == MAP_FAILED) {
        _glfwInputError(GLFW_PLATFORM_ERROR, "Wayland: mmap failed: %s", strerror(errno));
        close(fd);
        return false;
    }
    struct wl_shm_pool* pool = wl_shm_create_pool(_glfw.wl.shm, fd, decs.mapping.size);
    close(fd);
    size_t offset = 0;
#define a(which) alloc_buffer_pair(&decs.which.buffer, pool, decs.mapping.data, &offset)
    a(top); a(left); a(bottom); a(right);
#undef a
    wl_shm_pool_destroy(pool);
    create_shadow_tile(window);
    render_title_bar(window, true);
    render_edges(window);
    debug("Created decoration buffers at scale: %u vertical_height: %zu horizontal_width: %zu\n", scale, vertical_height, horizontal_width);
    return true;
}

void
free_csd_surfaces(_GLFWwindow *window) {
#define d(which) {\
    if (decs.which.subsurface) wl_subsurface_destroy(decs.which.subsurface); \
    decs.which.subsurface = NULL; \
    if (decs.which.surface) wl_surface_destroy(decs.which.surface); \
    decs.which.surface = NULL; \
}
    d(left); d(top); d(right); d(bottom);
#undef d
}

static void
free_csd_buffers(_GLFWwindow *window) {
#define d(which) { \
    if (decs.which.buffer.a) wl_buffer_destroy(decs.which.buffer.a); \
    if (decs.which.buffer.b) wl_buffer_destroy(decs.which.buffer.b); \
    memset(&decs.which.buffer, 0, sizeof(_GLFWWaylandBufferPair)); \
}
    d(left); d(top); d(right); d(bottom);
#undef d
    if (decs.mapping.data) munmap(decs.mapping.data, decs.mapping.size);
    decs.mapping.data = NULL; decs.mapping.size = 0;
}

static void
position_csd_surface(_GLFWWaylandCSDEdge *s, int x, int y, int scale) {
    wl_surface_set_buffer_scale(s->surface, scale);
    s->x = x; s->y = y;
    wl_subsurface_set_position(s->subsurface, s->x, s->y);
}

static void
create_csd_surfaces(_GLFWwindow *window, _GLFWWaylandCSDEdge *s) {
    s->surface = wl_compositor_create_surface(_glfw.wl.compositor);
    s->subsurface = wl_subcompositor_get_subsurface(_glfw.wl.subcompositor, s->surface, window->wl.surface);
}

#define damage_csd(which, xbuffer) \
    wl_surface_attach(decs.which.surface, xbuffer, 0, 0); \
    wl_surface_damage(decs.which.surface, 0, 0, decs.which.buffer.width, decs.which.buffer.height); \
    wl_surface_commit(decs.which.surface)

bool
ensure_csd_resources(_GLFWwindow *window) {
    if (!window->decorated || window->wl.decorations.serverSide) return false;
    const bool is_focused = window->id == _glfw.focusedWindowId;
    const bool focus_changed = is_focused != decs.for_window_state.focused;
    const bool size_changed = (
        decs.for_window_state.width != window->wl.width ||
        decs.for_window_state.height != window->wl.height ||
        decs.for_window_state.scale != window->wl.scale ||
        !decs.mapping.data
    );
    const bool needs_update = focus_changed || size_changed || !decs.left.surface;
    if (!needs_update) return false;
    if (size_changed) {
        free_csd_buffers(window);
        if (!create_shm_buffers(window)) return false;
    }

    int32_t x, y, scale = window->wl.scale < 1 ? 1 : window->wl.scale;
    x = 0; y = -decs.metrics.top;
    if (!decs.top.surface) create_csd_surfaces(window, &decs.top);
    position_csd_surface(&decs.top, x, y, scale);

    x = -decs.metrics.width; y = -decs.metrics.top;
    if (!decs.left.surface) create_csd_surfaces(window, &decs.left);
    position_csd_surface(&decs.left, x, y, scale);

    x = -decs.metrics.width; y = window->wl.height;
    if (!decs.bottom.surface) create_csd_surfaces(window, &decs.bottom);
    position_csd_surface(&decs.bottom, x, y, scale);

    x = window->wl.width; y = -decs.metrics.top;
    if (!decs.right.surface) create_csd_surfaces(window, &decs.right);
    position_csd_surface(&decs.right, x, y, scale);

    if (focus_changed) update_title_bar(window);
    damage_csd(top, decs.top.buffer.front);
    damage_csd(left, is_focused ? decs.left.buffer.front : decs.left.buffer.back);
    damage_csd(bottom, is_focused ? decs.bottom.buffer.front : decs.bottom.buffer.back);
    damage_csd(right, is_focused ? decs.right.buffer.front : decs.right.buffer.back);

    decs.for_window_state.width = window->wl.width;
    decs.for_window_state.height = window->wl.height;
    decs.for_window_state.scale = window->wl.scale;
    decs.for_window_state.focused = is_focused;
    return true;
}

void
free_all_csd_resources(_GLFWwindow *window) {
    free_csd_surfaces(window);
    free_csd_buffers(window);
    if (decs.shadow_tile.data) free(decs.shadow_tile.data);
    decs.shadow_tile.data = NULL;
}

void
change_csd_title(_GLFWwindow *window) {
    if (!window->decorated || window->wl.decorations.serverSide) return;
    if (ensure_csd_resources(window)) return;  // CSD were re-rendered for other reasons
    if (decs.top.surface) {
        update_title_bar(window);
        damage_csd(top, decs.top.buffer.front);
    }
}

void
set_csd_window_geometry(_GLFWwindow *window, int32_t *width, int32_t *height) {
    bool has_csd = window->decorated && !window->wl.decorations.serverSide && window->wl.decorations.left.surface && !(window->wl.toplevel_states & TOPLEVEL_STATE_FULLSCREEN);
    bool size_specified_by_compositor = *width > 0 && *height > 0;
    if (!size_specified_by_compositor) {
        *width = window->wl.user_requested_content_size.width;
        *height = window->wl.user_requested_content_size.height;
        if (has_csd) *height += decs.metrics.visible_titlebar_height;
    }
    decs.geometry.x = 0; decs.geometry.y = 0;
    decs.geometry.width = *width; decs.geometry.height = *height;
    if (has_csd) {
        decs.geometry.y = -decs.metrics.visible_titlebar_height;
        *height -= decs.metrics.visible_titlebar_height;
    }
}
