@cloudpss/template/src/compiler.ts

Lightweight string and object templating utilities with interpolation and formula support.

import { unwrapFromVmValue } from '@mirascript/mirascript';
import { buildError } from './builder.js';
import type { TemplateFunction, TemplateOptions } from './index.js';
import { parseTemplate } from './parser.js';
import {
    hasOwn,
    isError,
    isArrayBuffer,
    copyArrayBuffer,
    stringify,
    toString,
    isArrayBufferView,
    isArray,
} from './utils.js';

/** 模板序列号 */
let seq = 0;

const $init = [unwrapFromVmValue] as const;
const $unwrapFromVmValue = 0;

/** 创建模板 */
export class TemplateCompiler {
    constructor(
        readonly template: unknown,
        readonly options: Required<TemplateOptions>,
    ) {}
    private readonly $: unknown[] = [...$init];
    /** 放入 $，返回索引 */
    private use(value: unknown): number {
        this.$.push(value);
        return this.$.length - 1;
    }
    /** 构建数组 */
    private buildArray(arr: unknown[]): string {
        let result = '[';
        for (let i = 0, len = arr.length; i < len; i++) {
            result += this.buildValue(arr[i]);
            result += ',\n';
        }
        result += ']';
        return result;
    }
    /** 构建 ArrayBuffer */
    private buildArrayBuffer(buffer: ArrayBuffer | SharedArrayBuffer): string {
        const copy = copyArrayBuffer(buffer, 0);
        return `$[${this.use(copy)}].slice(0)`;
    }
    /** 构建 ArrayBufferView */
    private buildArrayBufferView(view: ArrayBufferView): string {
        const copy = copyArrayBuffer(view.buffer, view.byteOffset, view.byteLength);
        return `new ${view.constructor.name}($[${this.use(copy)}].slice(0))`;
    }
    /** 构建可能为模板的字符串 */
    private buildTemplate(value: string): string {
        const template = parseTemplate(value);
        if (typeof template == 'string') {
            return stringify(template);
        } else {
            return `$[${$unwrapFromVmValue}]($[${this.use(template.value)}](context))`;
        }
    }
    /** 构建对象 */
    private buildObject(obj: Record<string, unknown>): string {
        let result = '{';
        for (const key in obj) {
            if (!hasOwn(obj, key)) continue;
            result += '[';
            if (this.options.objectKeyMode === 'ignore') {
                result += stringify(key);
            } else {
                result += this.buildTemplate(key);
            }
            result += ']:';
            const value = obj[key];
            result += this.buildValue(value);
            result += ',\n';
        }
        result += '}';
        return result;
    }
    /** 构建值 */
    private buildValue(value: unknown): string {
        if (value === null) return 'null';
        if (value === undefined) return 'undefined';
        if (value === true) return 'true';
        if (value === false) return 'false';
        if (typeof value == 'function') return 'undefined';
        if (typeof value == 'symbol') return 'undefined';
        if (typeof value == 'bigint') return `${value}n`;
        if (typeof value == 'number') return String(value);
        if (typeof value == 'string') return this.buildTemplate(value);
        /* c8 ignore next */
        if (typeof value != 'object') throw new Error(`Unsupported value: ${toString(value)}`);
        if (value instanceof Date) return `new Date(${value.getTime()})`;
        if (value instanceof RegExp) return value.toString();
        if (isError(value)) return buildError(value);
        if (isArray(value)) return this.buildArray(value);
        if (isArrayBuffer(value)) return this.buildArrayBuffer(value);
        if (isArrayBufferView(value)) return this.buildArrayBufferView(value);
        return this.buildObject(value as Record<string, unknown>);
    }
    /** 构建模板 */
    build(): TemplateFunction {
        const source = this.buildValue(this.template);
        try {
            // eslint-disable-next-line @typescript-eslint/no-implied-eval, @typescript-eslint/no-unsafe-call
            const result = new Function(
                '$',
                [
                    `//# sourceURL=cloudpss-template[${seq++}]`, // sourceURL 用于调试
                    `return (context) => (${source});`,
                ].join('\n'),
            )(this.$) as TemplateFunction;
            return result;
            /* c8 ignore next 3 */
        } catch (e) {
            throw new Error(`Failed to compile template: ${source}\n${(e as Error).message}`, { cause: e });
        }
    }
}