sql-formatter/src/core/Indentation.js

Formats whitespaces in a SQL query to make it more readable

import repeat from "lodash/repeat";
import last from "lodash/last";

const INDENT_TYPE_TOP_LEVEL = "top-level";
const INDENT_TYPE_BLOCK_LEVEL = "block-level";

/**
 * Manages indentation levels.
 *
 * There are two types of indentation levels:
 *
 * - BLOCK_LEVEL : increased by open-parenthesis
 * - TOP_LEVEL : increased by RESERVED_TOPLEVEL words
 */
export default class Indentation {
    /**
     * @param {String} indent Indent value, default is "  " (2 spaces)
     */
    constructor(indent) {
        this.indent = indent || "  ";
        this.indentTypes = [];
    }

    /**
     * Returns current indentation string.
     * @return {String}
     */
    getIndent() {
        return repeat(this.indent, this.indentTypes.length);
    }

    /**
     * Increases indentation by one top-level indent.
     */
    increaseToplevel() {
        this.indentTypes.push(INDENT_TYPE_TOP_LEVEL);
    }

    /**
     * Increases indentation by one block-level indent.
     */
    increaseBlockLevel() {
        this.indentTypes.push(INDENT_TYPE_BLOCK_LEVEL);
    }

    /**
     * Decreases indentation by one top-level indent.
     * Does nothing when the previous indent is not top-level.
     */
    decreaseTopLevel() {
        if (last(this.indentTypes) === INDENT_TYPE_TOP_LEVEL) {
            this.indentTypes.pop();
        }
    }

    /**
     * Decreases indentation by one block-level indent.
     * If there are top-level indents within the block-level indent,
     * throws away these as well.
     */
    decreaseBlockLevel() {
        while (this.indentTypes.length > 0) {
            const type = this.indentTypes.pop();
            if (type !== INDENT_TYPE_TOP_LEVEL) {
                break;
            }
        }
    }
}