/*
 * Copyright (c) 2015-2018, IGN France.
 * Copyright (c) 2018-2026, Giro3D team.
 * SPDX-License-Identifier: MIT
 */

import type { ShaderMaterial } from 'three';

import PrecisionQualifier from './chunk/giro3d_precision_qualifiers.glsl';

const rePosition = new RegExp('gl_Position.*(?![^]*gl_Position)');
const reMain = new RegExp('[^\\w]*main[^\\w]*(void)?[^\\w]*{');

export default {
    patchMaterialForLogDepthSupport(material: ShaderMaterial): void {
        // Check if the shader does not already use the log depth buffer
        if (
            material.vertexShader.indexOf('USE_LOGARITHMIC_DEPTH_BUFFER') !== -1 ||
            material.vertexShader.indexOf('logdepthbuf_pars_vertex') !== -1
        ) {
            return;
        }

        // Add vertex shader log depth buffer header
        material.vertexShader = `#include <logdepthbuf_pars_vertex>\n#define EPSILON 1e-6\n${material.vertexShader}`;
        // Add log depth buffer code snippet after last gl_Position modification
        let re = rePosition.exec(material.vertexShader);
        if (re && re.length > 0) {
            const idx = re[0].length + re.index;
            material.vertexShader = `${material.vertexShader.slice(0, idx)}\n#include <logdepthbuf_vertex>\n${material.vertexShader.slice(idx)}`;
        }

        // Add fragment shader log depth buffer header
        material.fragmentShader = `${PrecisionQualifier}\n#include <logdepthbuf_pars_fragment>\n${material.fragmentShader}`;
        // Add log depth buffer code snippet at the first line of the main function
        re = reMain.exec(material.fragmentShader);
        if (re && re.length > 0) {
            const idx = re[0].length + re.index;
            material.fragmentShader = `${material.fragmentShader.slice(0, idx)}\n#include <logdepthbuf_fragment>\n${material.fragmentShader.slice(idx)}`;
        }

        material.defines = {
            USE_LOGARITHMIC_DEPTH_BUFFER: 1,
        };
    },
};