#!/usr/bin/env node

var path = require('path');
var fs = require('fs');
var mkdirp = require('mkdirp');

var shaderName = process.argv[2];
var inputPath = process.argv[3];
var outputPath = process.argv[4];

if (!shaderName || !inputPath || !outputPath) {
    console.warn('Not enough arguments.');
    console.warn('Usage: %s shaderName /path-to-shader-sources /output-path', path.basename(process.argv[1]));
    process.exit(1);
}

function applyPragmas(source, pragmas) {
    return source.replace(/#pragma mapbox: ([\w]+) ([\w]+) ([\w]+) ([\w]+)/g, (match, operation, precision, type, name) => {
        return pragmas[operation]
            .join("\n")
            .replace(/\{type\}/g, type)
            .replace(/\{precision\}/g, precision)
            .replace(/\{name\}/g, name);
    });
}

function vertexSource() {
    var prelude = fs.readFileSync(path.join(inputPath, '_prelude.vertex.glsl'));
    var source = fs.readFileSync(path.join(inputPath, shaderName + '.vertex.glsl'), 'utf8');
    return prelude + applyPragmas(source, {
        define: [
            "uniform lowp float a_{name}_t;",
            "attribute {precision} {type} a_{name}_min;",
            "attribute {precision} {type} a_{name}_max;",
            "varying {precision} {type} {name};"
        ],
        initialize: [
            "{name} = mix(a_{name}_min, a_{name}_max, a_{name}_t);"
        ]
    });
}

function fragmentSource() {
    var prelude = fs.readFileSync(path.join(inputPath, '_prelude.fragment.glsl'));
    var source = fs.readFileSync(path.join(inputPath, shaderName + '.fragment.glsl'), 'utf8');
    return prelude + applyPragmas(source, {
        define: [
            "varying {precision} {type} {name};"
        ],
        initialize: [
        ]
    });
}

var content = "#pragma once\n" +
"\n" +
"// NOTE: DO NOT CHANGE THIS FILE. IT IS AUTOMATICALLY GENERATED.\n" +
"\n" +
"#include <mbgl/gl/gl.hpp>\n" +
"\n" +
"namespace mbgl {\n" +
"namespace shaders {\n" +
"\n" +
"class " + shaderName + " {\n" +
"public:\n" +
"    static constexpr const char* name = \"" + shaderName + "\";\n" +
"    static constexpr const char* vertexSource = R\"MBGL_SHADER(\n" + vertexSource() + ")MBGL_SHADER\";\n" +
"    static constexpr const char* fragmentSource = R\"MBGL_SHADER(\n" + fragmentSource() + ")MBGL_SHADER\";\n" +
"};\n" +
"\n" +
"} // namespace shaders\n" +
"} // namespace mbgl\n";

mkdirp.sync(outputPath);
fs.writeFileSync(path.join(outputPath, shaderName + '.hpp'), content);