#include "pch.h"
#include "log.h"
#include "canvas.h"

void ui::Canvas::clear(const glm::vec4& c/*={0,0,0,1}*/)
{
    GLfloat cc[4];
    m_layers[m_current_layer_idx].m_rtt.bindFramebuffer();
    glGetFloatv(GL_COLOR_CLEAR_VALUE, cc);
    glClearColor(c.r, c.g, c.b, c.a);
    glClear(GL_COLOR_BUFFER_BIT);
    glViewport(0, 0, m_width, m_height);
    glClearColor(cc[0], cc[1], cc[2], cc[3]);
    m_layers[m_current_layer_idx].m_rtt.unbindFramebuffer();
}
void ui::Canvas::stroke_end()
{
    stroke_commit();
    m_current_stroke = nullptr;
    m_show_tmp = false;
}
void ui::Canvas::stroke_draw()
{
    if (!(m_current_stroke && m_current_stroke->has_sample()))
        return;

    m_dirty = true;

    m_tmp.bindFramebuffer();

    GLint vp[4];
    GLfloat cc[4];
    glGetIntegerv(GL_VIEWPORT, vp);
    glGetFloatv(GL_COLOR_CLEAR_VALUE, cc);

    glViewport(0, 0, m_width, m_height);

    auto proj = glm::ortho(0.f, (float)m_width, 0.f, (float)m_height, -1.f, 1.f);

    auto m_brush = m_current_stroke->m_brush;
    auto samples = m_current_stroke->compute_samples();
    auto& tex = TextureManager::get(m_brush.m_tex_id);
    tex.bind();
    m_sampler.bind(0);
    glActiveTexture(GL_TEXTURE1);
    m_tex.bind(); // bg, copy of framebuffer (copied before drawing)
    m_sampler_bg.bind(1);

    if (m_use_instanced)
    {
        glEnable(GL_BLEND);
        m_mesh.shader.use();
        m_mesh.shader.u_vec4(kShaderUniform::Col, m_brush.m_tip_color);
        m_mesh.shader.u_int(kShaderUniform::Tex, 0);
        m_mesh.draw(samples, proj);
    }
    else
    {
        glDisable(GL_BLEND);
        if (m_erase)
        {
            ShaderManager::use(ui::kShader::StrokeErase);
            //ShaderManager::u_vec4(kShaderUniform::Col, m_brush.m_tip_color);
        }
        else
        {
            ShaderManager::use(ui::kShader::Stroke);
            ShaderManager::u_vec4(kShaderUniform::Col, m_brush.m_tip_color);
        }
        ShaderManager::u_int(kShaderUniform::Tex, 0); // brush
        ShaderManager::u_int(kShaderUniform::TexBG, 1); // bg
        ShaderManager::u_vec2(kShaderUniform::Resolution, { m_width, m_height });
        for (const auto& s : samples)
        {
            auto unproject = [](glm::vec2 loc, glm::vec4 vp, glm::mat4 camera, glm::mat4 proj, glm::vec3& out_origin, glm::vec3& out_dir) {
                auto clip_space = glm::vec2(loc.x, vp.w - loc.y - 1.f) / vp.zw() * 2.f - 1.f;
                auto inv = glm::inverse(proj * camera);
                auto wp0 = inv * glm::vec4(clip_space, 0, 1);
                auto wp1 = inv * glm::vec4(clip_space, .5, 1);
                out_origin = (wp0 / wp0.w).xyz();
                out_dir = glm::normalize((wp1 / wp1.w).xyz() - out_origin);
            };
            auto intersect = [](glm::vec3 ray_origin, glm::vec3 ray_dir, glm::vec3 plane_origin, glm::vec3 plane_normal, glm::vec3& out_hit) {
                float den = glm::dot(ray_dir, plane_normal);
                if (den == 0)
                    return false;  // no intersection
                float num = glm::dot(plane_origin - ray_origin, plane_normal);
                float t = num / den;
                if (t > 0)
                    out_hit = ray_origin + ray_dir * t;
                else
                    // negative intersection
                    return false;
                return true;
            };
            glm::vec3 ray_origin, ray_dir;
            unproject(s.pos, { 0, 0, m_box.zw }, m_mv, m_proj, ray_origin, ray_dir);
            glm::vec3 plane_origin{ 0, 0, -1 }, plane_dir{ 0, 0, 1 };
            glm::vec3 hit;
            glm::vec2 fb_pos;
            if (intersect(ray_origin, ray_dir, plane_origin, plane_dir, hit))
            {
                glm::mat4 plane_camera = glm::lookAt(plane_origin, plane_dir, { 0, 1, 0 });
                glm::vec4 plane_local = plane_camera * glm::vec4(hit, 1);
                if (glm::abs(plane_local.x) < 0.5f && glm::abs(plane_local.y) < 0.5f)
                {
                    fb_pos.x = -(plane_local.x - 0.5f) * m_width;
                    fb_pos.y = (plane_local.y + 0.5f) * m_height;
                    LOG("draw %f %f", fb_pos.x, fb_pos.y);
                }
            }

            auto mvp = proj *
                glm::translate(glm::vec3(fb_pos, 0)) *
                glm::scale(glm::vec3(s.size, s.size, 1)) *
                glm::eulerAngleZ(s.angle);

            glm::vec4 P[4] {
                mvp * glm::vec4(glm::vec2(-.5f, -.5f), 0, 1.f), // A - bottom-left
                mvp * glm::vec4(glm::vec2(-.5f, +.5f), 0, 1.f), // B - top-left
                mvp * glm::vec4(glm::vec2(+.5f, +.5f), 0, 1.f), // C - top-right
                mvp * glm::vec4(glm::vec2(+.5f, -.5f), 0, 1.f), // D - bottom-right
            };

            auto mvp_inv = glm::inverse(proj);
            glm::vec4 P2[4]{
                mvp_inv * P[0],
                mvp_inv * P[1],
                mvp_inv * P[2],
                mvp_inv * P[3],
            };

            glm::vec2 bb_min(m_width, m_height);
            glm::vec2 bb_max(0, 0);
            for (int i = 0; i < 4; i++)
            {
                bb_min = glm::max({ 0, 0 }, glm::min(bb_min, P2[i].xy()));
                bb_max = glm::min({ m_width, m_height }, glm::max(bb_max, P2[i].xy()));
            }
            auto bb_sz = bb_max - bb_min;
            
            glm::vec2 pad(1);
            glm::ivec2 tex_pos = glm::clamp(glm::floor(bb_min) - pad , { 0, 0 }, { m_width, m_height });
            glm::ivec2 tex_sz  = glm::clamp(glm::ceil(bb_sz ) + pad*2.f, { 0, 0 }, (glm::vec2)(glm::ivec2(m_width, m_height) - tex_pos));
            glCopyTexSubImage2D(GL_TEXTURE_2D, 0, 
                tex_pos.x, tex_pos.y,
                tex_pos.x, tex_pos.y,
                tex_sz.x, tex_sz.y);
            
            m_box.xy = glm::min(m_box.xy(), (glm::vec2)tex_pos);
            m_box.zw = glm::max(m_box.zw(), (glm::vec2)(tex_pos + tex_sz));

            ShaderManager::u_mat4(kShaderUniform::MVP, glm::mat4());
            ShaderManager::u_float(kShaderUniform::Alpha, s.flow);
            m_plane_brush.update_vertices(P);
            m_plane_brush.draw_fill();
        }
    }

    m_tex.unbind();
    glActiveTexture(GL_TEXTURE0);
    m_sampler.unbind();
    m_sampler_bg.unbind();
    tex.unbind();

    glDisable(GL_BLEND);

    glViewport(vp[0], vp[1], vp[2], vp[3]);
    glClearColor(cc[0], cc[1], cc[2], cc[3]);

    m_tmp.unbindFramebuffer();
}
void ui::Canvas::stroke_commit()
{
    if (!m_dirty)
        return;
    m_dirty = false;

    m_layers[m_current_layer_idx].m_rtt.bindFramebuffer();
    
    // save image before commit
    glm::vec2 box_sz = m_box.zw() - m_box.xy();
    auto image = std::make_unique<uint8_t[]>(box_sz.x * box_sz.y * 4);
    glReadPixels(m_box.x, m_box.y, box_sz.x, box_sz.y, GL_RGBA, GL_UNSIGNED_BYTE, image.get());
    
    // copy to tmp2 for layer blending
    m_tex2.bind();
    glCopyTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, 0, 0, m_width, m_height);
    m_tex2.unbind();

    GLint vp[4];
    GLfloat cc[4];
    glGetIntegerv(GL_VIEWPORT, vp);
    glGetFloatv(GL_COLOR_CLEAR_VALUE, cc);

    glViewport(0, 0, m_width, m_height);
    GLboolean blend = glIsEnabled(GL_BLEND);
    glDisable(GL_BLEND);

    m_tmp.bindTexture();
    glActiveTexture(GL_TEXTURE1);
    m_tex2.bind();
    m_sampler.bind(0);
    m_sampler_bg.bind(1);
    if (m_erase)
    {
        ShaderManager::use(ui::kShader::Texture);
    }
    else
    {
        ShaderManager::use(ui::kShader::StrokeLayer);
        ShaderManager::u_int(kShaderUniform::TexBG, 1);
        ShaderManager::u_float(kShaderUniform::Alpha, m_current_stroke->m_brush.m_tip_opacity);
    }
    ShaderManager::u_int(kShaderUniform::Tex, 0);
    ShaderManager::u_mat4(kShaderUniform::MVP, glm::ortho(-.5f, .5f, -.5f, .5f, -1.f, 1.f));
    m_plane.draw_fill();
    m_sampler.unbind();
    m_sampler_bg.unbind();
    m_tex2.unbind();
    glActiveTexture(GL_TEXTURE0);
    m_tmp.unbindTexture();

    blend ? glEnable(GL_BLEND) : glDisable(GL_BLEND);

    glViewport(vp[0], vp[1], vp[2], vp[3]);
    glClearColor(cc[0], cc[1], cc[2], cc[3]);

    m_layers[m_current_layer_idx].m_rtt.unbindFramebuffer();
    
    // save history
    auto action = new ActionStroke;
    action->m_image = std::move(image);
    action->m_box = m_box;
    action->m_layer_idx = m_current_layer_idx;
    action->m_canvas = this;
    action->m_stroke = std::move(m_current_stroke);
    ActionManager::add(action);
}
void ui::Canvas::stroke_update(glm::vec2 point, float pressure)
{
    m_current_stroke->add_point(point, pressure);
}
void ui::Canvas::stroke_start(glm::vec2 point, float pressure, const ui::Brush& brush)
{
    m_current_stroke = std::make_unique<Stroke>();
    m_current_stroke->m_camera = { m_cam_rot, m_cam_fov };
    m_current_stroke->start(brush);
    m_current_stroke->add_point(point, pressure);
    
    m_box = glm::vec4(m_width, m_height, 0, 0); // reset bounding box
    
    if (m_erase)
    {
        m_layers[m_current_layer_idx].m_rtt.bindFramebuffer();
        m_tmp.bindTexture();
        glCopyTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, 0, 0, m_width, m_height);
        m_tmp.unbindTexture();
        m_layers[m_current_layer_idx].m_rtt.unbindFramebuffer();
    }
    else
    {
        m_tmp.bindFramebuffer();
        m_tmp.clear({ 0, 0, 0, 0 });
        m_tmp.unbindFramebuffer();
    }
    m_show_tmp = true;
}
void ui::Canvas::layer_add(std::string name)
{
    int idx = (int)m_layers.size();
    m_layers.emplace_back();
    m_layers.back().create(m_width, m_height, name);
    m_order.push_back(idx);
}
void ui::Canvas::layer_order(int idx, int pos)
{
    std::swap(m_order[idx], m_order[pos]);
}
void ui::Canvas::resize(int width, int height)
{
    m_width = width;
    m_height = height;
    m_tmp.create(width, height);
    m_tex.create(width, height);
    m_tex2.create(width, height);
    for (auto& l : m_layers)
    {
        l.create(width, height, "");
    }
}
bool ui::Canvas::create(int width, int height)
{
    m_width = width;
    m_height = height;
    m_tmp.create(width, height);
    m_tex.create(width, height);
    m_tex2.create(width, height); // TODO: destroy before recreating
    m_sampler.create();
    m_sampler_bg.create();
    m_plane.create<1>(1, 1);
    m_plane_brush.create<1>(1, 1);
    m_mesh.create();
    return true;
}