import {UBO_BINDINGS, UniformBuffer, std140Layout} from './uniform_buffer.ts';

import type {Context} from './context.ts';
import type {ProjectionData, RendererProjectionData} from '../geo/projection/projection_data.ts';

const layout = std140Layout([
    {name: 'u_projection_matrix', type: 'mat4'},
    {name: 'u_projection_fallback_matrix', type: 'mat4'},
    {name: 'u_projection_tile_mercator_coords', type: 'vec4'},
    {name: 'u_projection_clipping_plane', type: 'vec4'},
    {name: 'u_projection_transition', type: 'float'},
    {name: 'u_projection_clip_antimeridian', type: 'int'},
]);

const offsets = layout.offsets;

/**
 * @internal
 * The buffer behind the `ProjectionUBO` block in the shader preludes.
 */
export function createProjectionUniformBuffer(context: Context): UniformBuffer {
    return new UniformBuffer(context, UBO_BINDINGS.ProjectionUBO, layout);
}

function updateProjectionUniformBuffer(buffer: UniformBuffer, projectionData: ProjectionData): void {
    const f32 = buffer.pending;
    f32.set(projectionData.mainMatrix, offsets.u_projection_matrix);
    f32.set(projectionData.fallbackMatrix, offsets.u_projection_fallback_matrix);
    f32.set(projectionData.tileMercatorCoords, offsets.u_projection_tile_mercator_coords);
    f32.set(projectionData.clippingPlane, offsets.u_projection_clipping_plane);
    f32[offsets.u_projection_transition] = projectionData.projectionTransition;
    buffer.pendingWords[offsets.u_projection_clip_antimeridian] = projectionData.clipAntimeridian ? 1 : 0;
    buffer.upload();
}

export function bindProjectionUniformBuffer(context: Context, projectionData: ProjectionData & Pick<RendererProjectionData, 'uniformBufferKey'>): void {
    if (!projectionData) {
        context.projectionUniformBuffer.bind();
        return;
    }
    const key = projectionData.uniformBufferKey;
    if (key === undefined) {
        updateProjectionUniformBuffer(context.projectionUniformBuffer, projectionData);
        return;
    }
    const keyedBuffer = context.keyedProjectionUniformBuffers.get(key);
    if (keyedBuffer) {
        keyedBuffer.bind();
        return;
    }
    const buffer = context.freeProjectionUniformBuffers.pop() ?? createProjectionUniformBuffer(context);
    context.keyedProjectionUniformBuffers.set(key, buffer);
    updateProjectionUniformBuffer(buffer, projectionData);
}

export function releaseProjectionUniformBuffers(context: Context): void {
    context.freeProjectionUniformBuffers.push(...context.keyedProjectionUniformBuffers.values());
    context.keyedProjectionUniformBuffers.clear();
}

export function destroyProjectionUniformBuffers(context: Context): void {
    context.projectionUniformBuffer.destroy();
    for (const buffer of context.keyedProjectionUniformBuffers.values()) buffer.destroy();
    for (const buffer of context.freeProjectionUniformBuffers) buffer.destroy();
}