#include "viz/graph_renderer.h"
#include "viz/graph_types.h"

// gl_loader: en Linux es no-op (incluye GL headers con GL_GLEXT_PROTOTYPES);
// en Windows expone los punteros via #define gl* fn_gl* tras gl_loader_init().
#include "gfx/gl_loader.h"

#include <cstdlib>
#include <cstring>
#include <cstdio>
#include <cmath>

// ---------------------------------------------------------------------------
// Community palette (ABGR packed, 10 colors)
// ---------------------------------------------------------------------------
static const uint32_t k_palette[10] = {
    0xFF4CAF50, // green
    0xFFF44336, // red
    0xFF2196F3, // blue
    0xFFFF9800, // orange
    0xFF9C27B0, // purple
    0xFF00BCD4, // cyan
    0xFFFFEB3B, // yellow
    0xFFE91E63, // pink
    0xFF795548, // brown
    0xFF607D8B  // blue-grey
};

// ---------------------------------------------------------------------------
// Internal struct
// ---------------------------------------------------------------------------
struct GraphRenderer {
    unsigned int fbo;
    unsigned int texture;
    unsigned int rbo; // depth/stencil renderbuffer
    int width, height;

    // Node rendering (instanced quads)
    unsigned int node_vao, node_quad_vbo, node_instance_vbo;
    unsigned int node_shader;

    // Edge rendering (lines)
    unsigned int edge_vao, edge_vbo;
    unsigned int edge_shader;

    GraphRendererConfig config;
};

// ---------------------------------------------------------------------------
// Shader sources
// ---------------------------------------------------------------------------

// Node vertex shader — instanced unit quad
static const char* k_node_vert = R"(
#version 330 core
// Quad corners [-0.5, 0.5]
layout(location = 0) in vec2 a_quad;

// Per-instance: world position, size, RGBA color
layout(location = 1) in vec2  a_pos;
layout(location = 2) in float a_size;
layout(location = 3) in vec4  a_color;

out vec2  v_uv;
out vec4  v_color;

uniform vec2  u_viewport;   // (width, height) in pixels
uniform float u_scale;      // cam_zoom
uniform vec2  u_translate;  // (tx, ty) in pixels

void main() {
    // World -> screen (pixels)
    vec2 screen = a_pos * u_scale + u_translate;
    // Expand quad by node radius (size = diameter)
    screen += a_quad * a_size * u_scale;
    // Screen -> NDC
    vec2 ndc = (screen / u_viewport) * 2.0 - 1.0;
    ndc.y = -ndc.y; // flip Y (screen Y grows downward)
    gl_Position = vec4(ndc, 0.0, 1.0);
    v_uv    = a_quad + 0.5; // [0,1]
    v_color = a_color;
}
)";

// Node fragment shader — SDF circle with outline
static const char* k_node_frag = R"(
#version 330 core
in vec2 v_uv;
in vec4 v_color;

out vec4 frag_color;

uniform float u_outline_px;  // outline width in uv units
uniform float u_node_px;     // node diameter in pixels (= size * zoom)

void main() {
    // SDF circle centered at (0.5, 0.5) in uv space
    float dist = length(v_uv - 0.5);
    float r    = 0.5;

    // Anti-alias edge (in uv units; 1px ~ 1/u_node_px in uv space)
    float fwidth_uv = 1.5 / max(u_node_px, 1.0);

    float alpha = 1.0 - smoothstep(r - fwidth_uv, r, dist);
    if (alpha < 0.001) discard;

    // Outline ring
    float outline_uv = u_outline_px / max(u_node_px, 1.0);
    float outline    = smoothstep(r - outline_uv - fwidth_uv, r - outline_uv, dist);

    vec3 fill    = v_color.rgb;
    vec3 outline_col = mix(fill, vec3(1.0), 0.6); // lighter outline
    vec3 color   = mix(fill, outline_col, outline);

    frag_color = vec4(color, v_color.a * alpha);
}
)";

// Edge vertex shader
static const char* k_edge_vert = R"(
#version 330 core
layout(location = 0) in vec2 a_pos;
layout(location = 1) in vec4 a_color;

out vec4 v_color;

uniform vec2  u_viewport;
uniform float u_scale;
uniform vec2  u_translate;

void main() {
    vec2 screen = a_pos * u_scale + u_translate;
    vec2 ndc    = (screen / u_viewport) * 2.0 - 1.0;
    ndc.y = -ndc.y;
    gl_Position = vec4(ndc, 0.0, 1.0);
    v_color = a_color;
}
)";

// Edge fragment shader
static const char* k_edge_frag = R"(
#version 330 core
in vec4 v_color;
out vec4 frag_color;

void main() {
    frag_color = v_color;
}
)";

// ---------------------------------------------------------------------------
// Shader helpers
// ---------------------------------------------------------------------------
static unsigned int compile_shader(GLenum type, const char* src) {
    unsigned int s = glCreateShader(type);
    glShaderSource(s, 1, &src, nullptr);
    glCompileShader(s);
    int ok;
    glGetShaderiv(s, GL_COMPILE_STATUS, &ok);
    if (!ok) {
        char buf[512];
        glGetShaderInfoLog(s, sizeof(buf), nullptr, buf);
        fprintf(stderr, "[graph_renderer] shader compile error: %s\n", buf);
    }
    return s;
}

static unsigned int link_program(const char* vert_src, const char* frag_src) {
    unsigned int vs = compile_shader(GL_VERTEX_SHADER,   vert_src);
    unsigned int fs = compile_shader(GL_FRAGMENT_SHADER, frag_src);
    unsigned int prog = glCreateProgram();
    glAttachShader(prog, vs);
    glAttachShader(prog, fs);
    glLinkProgram(prog);
    int ok;
    glGetProgramiv(prog, GL_LINK_STATUS, &ok);
    if (!ok) {
        char buf[512];
        glGetProgramInfoLog(prog, sizeof(buf), nullptr, buf);
        fprintf(stderr, "[graph_renderer] program link error: %s\n", buf);
    }
    glDeleteShader(vs);
    glDeleteShader(fs);
    return prog;
}

// ---------------------------------------------------------------------------
// FBO helpers
// ---------------------------------------------------------------------------
static void create_fbo(GraphRenderer* r) {
    // Texture
    glGenTextures(1, &r->texture);
    glBindTexture(GL_TEXTURE_2D, r->texture);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, r->width, r->height, 0, GL_RGBA, GL_UNSIGNED_BYTE, nullptr);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    glBindTexture(GL_TEXTURE_2D, 0);

    // Depth renderbuffer
    glGenRenderbuffers(1, &r->rbo);
    glBindRenderbuffer(GL_RENDERBUFFER, r->rbo);
    glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT24, r->width, r->height);
    glBindRenderbuffer(GL_RENDERBUFFER, 0);

    // FBO
    glGenFramebuffers(1, &r->fbo);
    glBindFramebuffer(GL_FRAMEBUFFER, r->fbo);
    glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, r->texture, 0);
    glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, r->rbo);
    glBindFramebuffer(GL_FRAMEBUFFER, 0);
}

static void destroy_fbo(GraphRenderer* r) {
    glDeleteFramebuffers(1,  &r->fbo);
    glDeleteTextures(1,      &r->texture);
    glDeleteRenderbuffers(1, &r->rbo);
    r->fbo = r->texture = r->rbo = 0;
}

// ---------------------------------------------------------------------------
// Helper: unpack ABGR uint32 to float RGBA
// ---------------------------------------------------------------------------
static inline void abgr_to_rgba(uint32_t abgr, float& r, float& g, float& b, float& a) {
    // ABGR layout: bits 31-24 = A, 23-16 = B, 15-8 = G, 7-0 = R
    a = ((abgr >> 24) & 0xFF) / 255.0f;
    b = ((abgr >> 16) & 0xFF) / 255.0f;
    g = ((abgr >>  8) & 0xFF) / 255.0f;
    r = ((abgr      ) & 0xFF) / 255.0f;
}

// ---------------------------------------------------------------------------
// Public API
// ---------------------------------------------------------------------------

GraphRenderer* graph_renderer_create(int width, int height, const GraphRendererConfig& config) {
    GraphRenderer* r = new GraphRenderer();
    r->width  = width;
    r->height = height;
    r->config = config;

    // --- FBO ---
    create_fbo(r);

    // --- Node VAO ---
    // Unit quad: 4 vertices, each (x, y) in [-0.5, 0.5]
    static const float quad_verts[8] = {
        -0.5f, -0.5f,
         0.5f, -0.5f,
        -0.5f,  0.5f,
         0.5f,  0.5f,
    };

    glGenVertexArrays(1, &r->node_vao);
    glBindVertexArray(r->node_vao);

    // Quad VBO (location 0)
    glGenBuffers(1, &r->node_quad_vbo);
    glBindBuffer(GL_ARRAY_BUFFER, r->node_quad_vbo);
    glBufferData(GL_ARRAY_BUFFER, sizeof(quad_verts), quad_verts, GL_STATIC_DRAW);
    glEnableVertexAttribArray(0);
    glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 2 * sizeof(float), (void*)0);

    // Instance VBO (location 1,2,3 — position, size, color)
    glGenBuffers(1, &r->node_instance_vbo);
    glBindBuffer(GL_ARRAY_BUFFER, r->node_instance_vbo);
    // layout: x, y, size, r, g, b, a  — 7 floats per instance
    glEnableVertexAttribArray(1); // pos
    glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 7 * sizeof(float), (void*)0);
    glVertexAttribDivisor(1, 1);
    glEnableVertexAttribArray(2); // size
    glVertexAttribPointer(2, 1, GL_FLOAT, GL_FALSE, 7 * sizeof(float), (void*)(2 * sizeof(float)));
    glVertexAttribDivisor(2, 1);
    glEnableVertexAttribArray(3); // color
    glVertexAttribPointer(3, 4, GL_FLOAT, GL_FALSE, 7 * sizeof(float), (void*)(3 * sizeof(float)));
    glVertexAttribDivisor(3, 1);

    glBindVertexArray(0);

    // --- Edge VAO ---
    // Each edge: 2 vertices x (x, y, r, g, b, a) = 2 * 6 floats
    glGenVertexArrays(1, &r->edge_vao);
    glBindVertexArray(r->edge_vao);

    glGenBuffers(1, &r->edge_vbo);
    glBindBuffer(GL_ARRAY_BUFFER, r->edge_vbo);
    glEnableVertexAttribArray(0); // pos
    glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 6 * sizeof(float), (void*)0);
    glEnableVertexAttribArray(1); // color
    glVertexAttribPointer(1, 4, GL_FLOAT, GL_FALSE, 6 * sizeof(float), (void*)(2 * sizeof(float)));

    glBindVertexArray(0);

    // --- Shaders ---
    r->node_shader = link_program(k_node_vert, k_node_frag);
    r->edge_shader = link_program(k_edge_vert, k_edge_frag);

    return r;
}

void graph_renderer_destroy(GraphRenderer* r) {
    if (!r) return;
    destroy_fbo(r);
    glDeleteVertexArrays(1, &r->node_vao);
    glDeleteBuffers(1, &r->node_quad_vbo);
    glDeleteBuffers(1, &r->node_instance_vbo);
    glDeleteVertexArrays(1, &r->edge_vao);
    glDeleteBuffers(1, &r->edge_vbo);
    glDeleteProgram(r->node_shader);
    glDeleteProgram(r->edge_shader);
    delete r;
}

void graph_renderer_resize(GraphRenderer* r, int width, int height) {
    if (!r) return;
    if (r->width == width && r->height == height) return;
    r->width  = width;
    r->height = height;
    destroy_fbo(r);
    create_fbo(r);
}

unsigned int graph_renderer_draw(GraphRenderer* r, const GraphData& graph,
                                  float cam_x, float cam_y, float cam_zoom) {
    if (!r) return 0;

    // --- Save GL state ---
    GLint prev_fbo;
    glGetIntegerv(GL_FRAMEBUFFER_BINDING, &prev_fbo);
    GLint prev_viewport[4];
    glGetIntegerv(GL_VIEWPORT, prev_viewport);

    // --- Bind FBO ---
    glBindFramebuffer(GL_FRAMEBUFFER, r->fbo);
    glViewport(0, 0, r->width, r->height);

    // Clear with bg_color (ABGR)
    float bg_a, bg_b, bg_g, bg_cr;
    abgr_to_rgba(r->config.bg_color, bg_cr, bg_g, bg_b, bg_a);
    glClearColor(bg_cr, bg_g, bg_b, bg_a);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    // Enable blending for anti-aliasing and transparency
    glEnable(GL_BLEND);
    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

    // View transform: world -> screen pixels
    // tx = -cam_x * scale + width/2
    // ty = -cam_y * scale + height/2
    float scale = cam_zoom;
    float tx = -cam_x * scale + (float)r->width  * 0.5f;
    float ty = -cam_y * scale + (float)r->height * 0.5f;

    // ----------------------------------------------------------------
    // Draw edges
    // ----------------------------------------------------------------
    if (graph.edge_count > 0 && graph.edges && graph.nodes) {
        // Pack: 2 vertices per edge, each vertex = (x, y, r, g, b, a) = 6 floats
        const int floats_per_edge = 2 * 6;
        float* edge_buf = (float*)malloc((size_t)graph.edge_count * floats_per_edge * sizeof(float));
        int vi = 0;
        for (int i = 0; i < graph.edge_count; ++i) {
            const GraphEdge& e = graph.edges[i];
            uint32_t ecol = e.color != 0 ? e.color : 0xFF888888u; // default gray
            float er, eg, eb, ea;
            abgr_to_rgba(ecol, er, eg, eb, ea);
            ea *= r->config.edge_alpha;

            if (e.source < (uint32_t)graph.node_count && e.target < (uint32_t)graph.node_count) {
                const GraphNode& ns = graph.nodes[e.source];
                const GraphNode& nt = graph.nodes[e.target];

                // Source vertex
                edge_buf[vi++] = ns.x; edge_buf[vi++] = ns.y;
                edge_buf[vi++] = er;   edge_buf[vi++] = eg;
                edge_buf[vi++] = eb;   edge_buf[vi++] = ea;
                // Target vertex
                edge_buf[vi++] = nt.x; edge_buf[vi++] = nt.y;
                edge_buf[vi++] = er;   edge_buf[vi++] = eg;
                edge_buf[vi++] = eb;   edge_buf[vi++] = ea;
            }
        }

        glUseProgram(r->edge_shader);
        glUniform2f(glGetUniformLocation(r->edge_shader, "u_viewport"), (float)r->width, (float)r->height);
        glUniform1f(glGetUniformLocation(r->edge_shader, "u_scale"),    scale);
        glUniform2f(glGetUniformLocation(r->edge_shader, "u_translate"), tx, ty);

        glLineWidth(r->config.edge_width);

        glBindVertexArray(r->edge_vao);
        glBindBuffer(GL_ARRAY_BUFFER, r->edge_vbo);
        glBufferData(GL_ARRAY_BUFFER, vi * (int)sizeof(float), edge_buf, GL_DYNAMIC_DRAW);
        glDrawArrays(GL_LINES, 0, vi / 6);
        glBindVertexArray(0);

        free(edge_buf);
    }

    // ----------------------------------------------------------------
    // Draw nodes (instanced quads)
    // ----------------------------------------------------------------
    if (graph.node_count > 0 && graph.nodes) {
        // Pack: 7 floats per node: x, y, size, r, g, b, a
        float* node_buf = (float*)malloc((size_t)graph.node_count * 7 * sizeof(float));
        for (int i = 0; i < graph.node_count; ++i) {
            const GraphNode& n = graph.nodes[i];
            uint32_t ncol = n.color != 0 ? n.color : k_palette[n.community % 10];
            float nr, ng, nb, na;
            abgr_to_rgba(ncol, nr, ng, nb, na);

            float sz = n.size > 0.0f ? n.size : 4.0f;
            float* p = node_buf + i * 7;
            p[0] = n.x; p[1] = n.y; p[2] = sz;
            p[3] = nr;  p[4] = ng;  p[5] = nb; p[6] = na;
        }

        glUseProgram(r->node_shader);
        glUniform2f(glGetUniformLocation(r->node_shader, "u_viewport"),  (float)r->width, (float)r->height);
        glUniform1f(glGetUniformLocation(r->node_shader, "u_scale"),     scale);
        glUniform2f(glGetUniformLocation(r->node_shader, "u_translate"), tx, ty);
        glUniform1f(glGetUniformLocation(r->node_shader, "u_outline_px"), r->config.node_outline);

        glBindVertexArray(r->node_vao);
        glBindBuffer(GL_ARRAY_BUFFER, r->node_instance_vbo);
        glBufferData(GL_ARRAY_BUFFER, graph.node_count * 7 * (int)sizeof(float), node_buf, GL_DYNAMIC_DRAW);

        // Draw 4 vertices (triangle strip quad) x node_count instances
        // Pass per-instance node_px uniform via the average size (approximation)
        // For exact per-node pixel size we'd need a texture or another approach;
        // use a uniform average for AA quality — good enough for most graphs.
        float avg_px = 8.0f * scale; // rough estimate
        glUniform1f(glGetUniformLocation(r->node_shader, "u_node_px"), avg_px);

        glDrawArraysInstanced(GL_TRIANGLE_STRIP, 0, 4, graph.node_count);
        glBindVertexArray(0);

        free(node_buf);
    }

    // --- Restore GL state ---
    glDisable(GL_BLEND);
    glBindFramebuffer(GL_FRAMEBUFFER, (GLuint)prev_fbo);
    glViewport(prev_viewport[0], prev_viewport[1], prev_viewport[2], prev_viewport[3]);

    return r->texture;
}