#include "clay.h"
#include <SDL3/SDL_main.h>
#include <SDL3/SDL.h>
#include <SDL3_ttf/SDL_ttf.h>
#include <SDL3_image/SDL_image.h>

typedef struct {
    SDL_Renderer *renderer;
    TTF_TextEngine *textEngine;
    TTF_Font **fonts;
} Clay_SDL3RendererData;

/* Global for convenience. Even in 4K this is enough for smooth curves (low radius or rect size coupled with
 * no AA or low resolution might make it appear as jagged curves) */
static int NUM_CIRCLE_SEGMENTS = 16;

//all rendering is performed by a single SDL call, avoiding multiple RenderRect + plumbing choice for circles.
static void SDL_Clay_RenderFillRoundedRect(Clay_SDL3RendererData *rendererData, const SDL_FRect rect, const float cornerRadius, const Clay_Color _color) {
    const SDL_FColor color = { _color.r/255, _color.g/255, _color.b/255, _color.a/255 };

    int indexCount = 0, vertexCount = 0;

    const float minRadius = SDL_min(rect.w, rect.h) / 2.0f;
    const float clampedRadius = SDL_min(cornerRadius, minRadius);

    const int numCircleSegments = SDL_max(NUM_CIRCLE_SEGMENTS, (int) clampedRadius * 0.5f);

    int totalVertices = 4 + (4 * (numCircleSegments * 2)) + 2*4;
    int totalIndices = 6 + (4 * (numCircleSegments * 3)) + 6*4;

    SDL_Vertex vertices[totalVertices];
    int indices[totalIndices];

    //define center rectangle
    vertices[vertexCount++] = (SDL_Vertex){ {rect.x + clampedRadius, rect.y + clampedRadius}, color, {0, 0} }; //0 center TL
    vertices[vertexCount++] = (SDL_Vertex){ {rect.x + rect.w - clampedRadius, rect.y + clampedRadius}, color, {1, 0} }; //1 center TR
    vertices[vertexCount++] = (SDL_Vertex){ {rect.x + rect.w - clampedRadius, rect.y + rect.h - clampedRadius}, color, {1, 1} }; //2 center BR
    vertices[vertexCount++] = (SDL_Vertex){ {rect.x + clampedRadius, rect.y + rect.h - clampedRadius}, color, {0, 1} }; //3 center BL

    indices[indexCount++] = 0;
    indices[indexCount++] = 1;
    indices[indexCount++] = 3;
    indices[indexCount++] = 1;
    indices[indexCount++] = 2;
    indices[indexCount++] = 3;

    //define rounded corners as triangle fans
    const float step = (SDL_PI_F/2) / numCircleSegments;
    for (int i = 0; i < numCircleSegments; i++) {
        const float angle1 = (float)i * step;
        const float angle2 = ((float)i + 1.0f) * step;

        for (int j = 0; j < 4; j++) {  // Iterate over four corners
            float cx, cy, signX, signY;

            switch (j) {
                case 0: cx = rect.x + clampedRadius; cy = rect.y + clampedRadius; signX = -1; signY = -1; break; // Top-left
                case 1: cx = rect.x + rect.w - clampedRadius; cy = rect.y + clampedRadius; signX = 1; signY = -1; break; // Top-right
                case 2: cx = rect.x + rect.w - clampedRadius; cy = rect.y + rect.h - clampedRadius; signX = 1; signY = 1; break; // Bottom-right
                case 3: cx = rect.x + clampedRadius; cy = rect.y + rect.h - clampedRadius; signX = -1; signY = 1; break; // Bottom-left
                default: return;
            }

            vertices[vertexCount++] = (SDL_Vertex){ {cx + SDL_cosf(angle1) * clampedRadius * signX, cy + SDL_sinf(angle1) * clampedRadius * signY}, color, {0, 0} };
            vertices[vertexCount++] = (SDL_Vertex){ {cx + SDL_cosf(angle2) * clampedRadius * signX, cy + SDL_sinf(angle2) * clampedRadius * signY}, color, {0, 0} };

            indices[indexCount++] = j;  // Connect to corresponding central rectangle vertex
            indices[indexCount++] = vertexCount - 2;
            indices[indexCount++] = vertexCount - 1;
        }
    }

    //Define edge rectangles
    // Top edge
    vertices[vertexCount++] = (SDL_Vertex){ {rect.x + clampedRadius, rect.y}, color, {0, 0} }; //TL
    vertices[vertexCount++] = (SDL_Vertex){ {rect.x + rect.w - clampedRadius, rect.y}, color, {1, 0} }; //TR

    indices[indexCount++] = 0;
    indices[indexCount++] = vertexCount - 2; //TL
    indices[indexCount++] = vertexCount - 1; //TR
    indices[indexCount++] = 1;
    indices[indexCount++] = 0;
    indices[indexCount++] = vertexCount - 1; //TR
    // Right edge
    vertices[vertexCount++] = (SDL_Vertex){ {rect.x + rect.w, rect.y + clampedRadius}, color, {1, 0} }; //RT
    vertices[vertexCount++] = (SDL_Vertex){ {rect.x + rect.w, rect.y + rect.h - clampedRadius}, color, {1, 1} }; //RB

    indices[indexCount++] = 1;
    indices[indexCount++] = vertexCount - 2; //RT
    indices[indexCount++] = vertexCount - 1; //RB
    indices[indexCount++] = 2;
    indices[indexCount++] = 1;
    indices[indexCount++] = vertexCount - 1; //RB
    // Bottom edge
    vertices[vertexCount++] = (SDL_Vertex){ {rect.x + rect.w - clampedRadius, rect.y + rect.h}, color, {1, 1} }; //BR
    vertices[vertexCount++] = (SDL_Vertex){ {rect.x + clampedRadius, rect.y + rect.h}, color, {0, 1} }; //BL

    indices[indexCount++] = 2;
    indices[indexCount++] = vertexCount - 2; //BR
    indices[indexCount++] = vertexCount - 1; //BL
    indices[indexCount++] = 3;
    indices[indexCount++] = 2;
    indices[indexCount++] = vertexCount - 1; //BL
    // Left edge
    vertices[vertexCount++] = (SDL_Vertex){ {rect.x, rect.y + rect.h - clampedRadius}, color, {0, 1} }; //LB
    vertices[vertexCount++] = (SDL_Vertex){ {rect.x, rect.y + clampedRadius}, color, {0, 0} }; //LT

    indices[indexCount++] = 3;
    indices[indexCount++] = vertexCount - 2; //LB
    indices[indexCount++] = vertexCount - 1; //LT
    indices[indexCount++] = 0;
    indices[indexCount++] = 3;
    indices[indexCount++] = vertexCount - 1; //LT

    // Render everything
    SDL_RenderGeometry(rendererData->renderer, NULL, vertices, vertexCount, indices, indexCount);
}

static void SDL_Clay_RenderArc(Clay_SDL3RendererData *rendererData, const SDL_FPoint center, const float radius, const float startAngle, const float endAngle, const float thickness, const Clay_Color color) {
    SDL_SetRenderDrawColor(rendererData->renderer, color.r, color.g, color.b, color.a);

    const float radStart = startAngle * (SDL_PI_F / 180.0f);
    const float radEnd = endAngle * (SDL_PI_F / 180.0f);

    const int numCircleSegments = SDL_max(NUM_CIRCLE_SEGMENTS, (int)(radius * 1.5f)); //increase circle segments for larger circles, 1.5 is arbitrary.

    const float angleStep = (radEnd - radStart) / (float)numCircleSegments;
    const float thicknessStep = 0.4f; //arbitrary value to avoid overlapping lines. Changing THICKNESS_STEP or numCircleSegments might cause artifacts.

    for (float t = thicknessStep; t < thickness - thicknessStep; t += thicknessStep) {
        SDL_FPoint points[numCircleSegments + 1];
        const float clampedRadius = SDL_max(radius - t, 1.0f);

        for (int i = 0; i <= numCircleSegments; i++) {
            const float angle = radStart + i * angleStep;
            points[i] = (SDL_FPoint){
                    SDL_roundf(center.x + SDL_cosf(angle) * clampedRadius),
                    SDL_roundf(center.y + SDL_sinf(angle) * clampedRadius) };
        }
        SDL_RenderLines(rendererData->renderer, points, numCircleSegments + 1);
    }
}

SDL_Rect currentClippingRectangle;

static void SDL_Clay_RenderClayCommands(Clay_SDL3RendererData *rendererData, Clay_RenderCommandArray *rcommands)
{
    for (size_t i = 0; i < rcommands->length; i++) {
        Clay_RenderCommand *rcmd = Clay_RenderCommandArray_Get(rcommands, i);
        const Clay_BoundingBox bounding_box = rcmd->boundingBox;
        const SDL_FRect rect = { (int)bounding_box.x, (int)bounding_box.y, (int)bounding_box.width, (int)bounding_box.height };

        switch (rcmd->commandType) {
            case CLAY_RENDER_COMMAND_TYPE_RECTANGLE: {
                Clay_RectangleRenderData *config = &rcmd->renderData.rectangle;
                SDL_SetRenderDrawBlendMode(rendererData->renderer, SDL_BLENDMODE_BLEND);
                SDL_SetRenderDrawColor(rendererData->renderer, config->backgroundColor.r, config->backgroundColor.g, config->backgroundColor.b, config->backgroundColor.a);
                if (config->cornerRadius.topLeft > 0) {
                    SDL_Clay_RenderFillRoundedRect(rendererData, rect, config->cornerRadius.topLeft, config->backgroundColor);
                } else {
                    SDL_RenderFillRect(rendererData->renderer, &rect);
                }
            } break;
            case CLAY_RENDER_COMMAND_TYPE_TEXT: {
                Clay_TextRenderData *config = &rcmd->renderData.text;
                TTF_Font *font = rendererData->fonts[config->fontId];
                TTF_Text *text = TTF_CreateText(rendererData->textEngine, font, config->stringContents.chars, config->stringContents.length);
                TTF_SetTextColor(text, config->textColor.r, config->textColor.g, config->textColor.b, config->textColor.a);
                TTF_DrawRendererText(text, rect.x, rect.y);
                TTF_DestroyText(text);
            } break;
            case CLAY_RENDER_COMMAND_TYPE_BORDER: {
                Clay_BorderRenderData *config = &rcmd->renderData.border;

                const float minRadius = SDL_min(rect.w, rect.h) / 2.0f;
                const Clay_CornerRadius clampedRadii = {
                    .topLeft = SDL_min(config->cornerRadius.topLeft, minRadius),
                    .topRight = SDL_min(config->cornerRadius.topRight, minRadius),
                    .bottomLeft = SDL_min(config->cornerRadius.bottomLeft, minRadius),
                    .bottomRight = SDL_min(config->cornerRadius.bottomRight, minRadius)
                };
                //edges
                SDL_SetRenderDrawColor(rendererData->renderer, config->color.r, config->color.g, config->color.b, config->color.a);
                if (config->width.left > 0) {
                    const float starting_y = rect.y + clampedRadii.topLeft;
                    const float length = rect.h - clampedRadii.topLeft - clampedRadii.bottomLeft;
                    SDL_FRect line = { rect.x, starting_y, config->width.left, length };
                    SDL_RenderFillRect(rendererData->renderer, &line);
                }
                if (config->width.right > 0) {
                    const float starting_x = rect.x + rect.w - (float)config->width.right;
                    const float starting_y = rect.y + clampedRadii.topRight;
                    const float length = rect.h - clampedRadii.topRight - clampedRadii.bottomRight;
                    SDL_FRect line = { starting_x, starting_y, config->width.right, length };
                    SDL_RenderFillRect(rendererData->renderer, &line);
                }
                if (config->width.top > 0) {
                    const float starting_x = rect.x + clampedRadii.topLeft;
                    const float length = rect.w - clampedRadii.topLeft - clampedRadii.topRight;
                    SDL_FRect line = { starting_x, rect.y, length, config->width.top };
                    SDL_RenderFillRect(rendererData->renderer, &line);
                }
                if (config->width.bottom > 0) {
                    const float starting_x = rect.x + clampedRadii.bottomLeft;
                    const float starting_y = rect.y + rect.h - (float)config->width.bottom;
                    const float length = rect.w - clampedRadii.bottomLeft - clampedRadii.bottomRight;
                    SDL_FRect line = { starting_x, starting_y, length, config->width.bottom };
                    SDL_SetRenderDrawColor(rendererData->renderer, config->color.r, config->color.g, config->color.b, config->color.a);
                    SDL_RenderFillRect(rendererData->renderer, &line);
                }
                //corners
                if (config->cornerRadius.topLeft > 0) {
                    const float centerX = rect.x + clampedRadii.topLeft -1;
                    const float centerY = rect.y + clampedRadii.topLeft;
                    SDL_Clay_RenderArc(rendererData, (SDL_FPoint){centerX, centerY}, clampedRadii.topLeft,
                        180.0f, 270.0f, config->width.top, config->color);
                }
                if (config->cornerRadius.topRight > 0) {
                    const float centerX = rect.x + rect.w - clampedRadii.topRight -1;
                    const float centerY = rect.y + clampedRadii.topRight;
                    SDL_Clay_RenderArc(rendererData, (SDL_FPoint){centerX, centerY}, clampedRadii.topRight,
                        270.0f, 360.0f, config->width.top, config->color);
                }
                if (config->cornerRadius.bottomLeft > 0) {
                    const float centerX = rect.x + clampedRadii.bottomLeft -1;
                    const float centerY = rect.y + rect.h - clampedRadii.bottomLeft -1;
                    SDL_Clay_RenderArc(rendererData, (SDL_FPoint){centerX, centerY}, clampedRadii.bottomLeft,
                        90.0f, 180.0f, config->width.bottom, config->color);
                }
                if (config->cornerRadius.bottomRight > 0) {
                    const float centerX = rect.x + rect.w - clampedRadii.bottomRight -1; //TODO: why need to -1 in all calculations???
                    const float centerY = rect.y + rect.h - clampedRadii.bottomRight -1;
                    SDL_Clay_RenderArc(rendererData, (SDL_FPoint){centerX, centerY}, clampedRadii.bottomRight,
                        0.0f, 90.0f, config->width.bottom, config->color);
                }

            } break;
            case CLAY_RENDER_COMMAND_TYPE_SCISSOR_START: {
                Clay_BoundingBox boundingBox = rcmd->boundingBox;
                currentClippingRectangle = (SDL_Rect) {
                        .x = boundingBox.x,
                        .y = boundingBox.y,
                        .w = boundingBox.width,
                        .h = boundingBox.height,
                };
                SDL_SetRenderClipRect(rendererData->renderer, &currentClippingRectangle);
                break;
            }
            case CLAY_RENDER_COMMAND_TYPE_SCISSOR_END: {
                SDL_SetRenderClipRect(rendererData->renderer, NULL);
                break;
            }
            case CLAY_RENDER_COMMAND_TYPE_IMAGE: {
                SDL_Surface *image = (SDL_Surface *)rcmd->renderData.image.imageData;
                SDL_Texture *texture = SDL_CreateTextureFromSurface(rendererData->renderer, image);
                const SDL_FRect dest = { rect.x, rect.y, rect.w, rect.h };

                SDL_RenderTexture(rendererData->renderer, texture, NULL, &dest);
                SDL_DestroyTexture(texture);
                break;
            }
            default:
                SDL_Log("Unknown render command type: %d", rcmd->commandType);
        }
    }
}