Allow users to have complex logic in templates

src/helpers/case.ts

@@ -0,0 +1,16 @@
+import { HandlebarsHelper, HelperConstructorBlock } from "./helper";
+
+export const caseHelper: HelperConstructorBlock = ctx => {
+    return new HandlebarsHelper("case", (type, rawV1): string => {
+        const v1 = new String(rawV1).toString();
+
+        switch (type) {
+            case "upper":
+                return v1.toUpperCase();
+            case "lower":
+                return v1.toLowerCase();
+            default:
+                throw new Error(`Invalid case type used with case: ${type}`);
+        }
+    });
+};

src/helpers/compare.ts

@@ -0,0 +1,42 @@
+import { HandlebarsHelper, HelperConstructorBlock } from "./helper";
+
+export const compareHelper: HelperConstructorBlock = ctx => {
+    return new HandlebarsHelper("compare", (v1, operator, v2): boolean => {
+        switch (operator) {
+            case "==":
+            case "eq":
+            case "equals":
+                return (v1 == v2);
+            case "===":
+            case "seq":
+            case "strictly-equals":
+                return (v1 === v2);
+            case "!=":
+            case "ne":
+            case "not-equals":
+                return (v1 != v2);
+            case "!==":
+            case "sne":
+            case "strictly-not-equals":
+                return (v1 !== v2);
+            case "<":
+            case "lt":
+            case "less-than":
+                return (v1 < v2);
+            case "<=":
+            case "lte":
+            case "less-than-equals":
+                return (v1 <= v2);
+            case ">":
+            case "gt":
+            case "greater-than":
+                return (v1 > v2);
+            case ">=":
+            case "gte":
+            case "greater-than-equals":
+                return (v1 >= v2);
+            default:
+                throw new Error(`Invalid comparison operator used with compare: ${operator}`);
+        }
+    });
+};

src/helpers/condition.ts

@@ -0,0 +1,19 @@
+import { HandlebarsHelper, HelperConstructorBlock } from "./helper";
+
+export const conditionHelper: HelperConstructorBlock = ctx => {
+    return new HandlebarsHelper("condition", (v1, operator, v2): boolean => {
+        switch (operator) {
+            case "!":
+            case "not":
+                return !v1;
+            case "&&":
+            case "and":
+                return (v1 && v2);
+            case "||":
+            case "or":
+                return (v1 || v2);
+            default:
+                throw new Error(`Invalid operator used with condition: ${operator}`);
+        }
+    });
+};

src/helpers/context.ts

@@ -0,0 +1,9 @@
+import { DateAndTimeUtils } from "../utils/dateAndTime";
+
+export class HelperContext {
+    public dateAndTimeUtils: DateAndTimeUtils;
+
+    constructor(dateUtils: DateAndTimeUtils) {
+        this.dateAndTimeUtils = dateUtils;
+    }
+}

src/helpers/custom_datetime.ts

@@ -0,0 +1,7 @@
+import { HandlebarsHelper, HelperConstructorBlock } from "./helper";
+
+export const customDatetimeHelper: HelperConstructorBlock = ctx => {
+    return new HandlebarsHelper("custom_datetime", (options) => {
+        return ctx.dateAndTimeUtils.getCurrentTime(options.fn(this));
+    });
+};

src/helpers/datetime.ts

@@ -0,0 +1,94 @@
+import { HandlebarsHelper, HelperConstructorBlock } from "./helper";
+import { AttributeValueType, AttributeDefinition, AttributeParser } from "./utils/attributes";
+import * as moment from "moment";
+
+const FORMAT = "format";
+const SET_DATE = "set_date";
+const SET_TIME = "set_time";
+const DELTA_YEARS = "delta_years";
+const DELTA_MONTHS = "delta_months";
+const DELTA_DAYS = "delta_days";
+const DELTA_HOURS = "delta_hours";
+const DELTA_MINUTES = "delta_minutes";
+const DELTA_SECONDS = "delta_seconds";
+
+export const datetimeHelper: HelperConstructorBlock = (ctx) => {
+    const schema: AttributeDefinition[] = [
+        {
+            name: FORMAT,
+            valueType: AttributeValueType.String,
+            defaultValue: ctx.dateAndTimeUtils.getDateTimeFormat()
+        },
+        {
+            name: SET_DATE,
+            valueType: AttributeValueType.String,
+            defaultValue: ""
+        },
+        {
+            name: SET_TIME,
+            valueType: AttributeValueType.String,
+            defaultValue: ""
+        },
+        {
+            name: DELTA_YEARS,
+            valueType: AttributeValueType.Number,
+            defaultValue: 0
+        },
+        {
+            name: DELTA_MONTHS,
+            valueType: AttributeValueType.Number,
+            defaultValue: 0
+        },
+        {
+            name: DELTA_DAYS,
+            valueType: AttributeValueType.Number,
+            defaultValue: 0
+        },
+        {
+            name: DELTA_HOURS,
+            valueType: AttributeValueType.Number,
+            defaultValue: 0
+        },
+        {
+            name: DELTA_MINUTES,
+            valueType: AttributeValueType.Number,
+            defaultValue: 0
+        },
+        {
+            name: DELTA_SECONDS,
+            valueType: AttributeValueType.Number,
+            defaultValue: 0
+        }
+    ];
+
+    return new HandlebarsHelper("datetime", function (options) {
+        const parser = new AttributeParser(schema);
+        const attrs = parser.parse(options.hash);
+
+        const now = moment(new Date().getTime());
+
+        if (attrs[SET_DATE]) {
+            const parsedDate = ctx.dateAndTimeUtils.parseDate(attrs[SET_DATE] as string, ctx.dateAndTimeUtils.getDateFormat());
+            now.set("date", parsedDate.date);
+            now.set("month", parsedDate.month);
+            now.set("year", parsedDate.year);
+        }
+
+        if (attrs[SET_TIME]) {
+            const parsedTime = ctx.dateAndTimeUtils.parseTime(attrs[SET_TIME] as string, ctx.dateAndTimeUtils.getTimeFormat());
+            now.set("hours", parsedTime.hours);
+            now.set("minutes", parsedTime.minutes);
+            now.set("seconds", 0);
+            now.set("milliseconds", 0);
+        }
+
+        now.add(attrs[DELTA_YEARS] as number, "years");
+        now.add(attrs[DELTA_MONTHS] as number, "months");
+        now.add(attrs[DELTA_DAYS] as number, "days");
+        now.add(attrs[DELTA_HOURS] as number, "hours");
+        now.add(attrs[DELTA_MINUTES] as number, "minutes");
+        now.add(attrs[DELTA_SECONDS] as number, "seconds");
+
+        return ctx.dateAndTimeUtils.formatMsToLocal(now.toDate().getTime(), attrs[FORMAT] as string);
+    });
+};

src/helpers/helper.ts

@@ -0,0 +1,21 @@
+import * as Handlebars from "handlebars/dist/handlebars";
+import { HelperContext } from "./context";
+
+export type HelperConstructorBlock = (ctx: HelperContext) => HandlebarsHelper;
+
+// eslint-disable-next-line @typescript-eslint/no-explicit-any
+type HelperImpl = (...args: Array<any>) => any;
+
+export class HandlebarsHelper {
+    private tag: string;
+    private impl: HelperImpl;
+
+    constructor(tag: string, impl: HelperImpl) {
+        this.tag = tag;
+        this.impl = impl;
+    }
+
+    public register(): void {
+        Handlebars.registerHelper(this.tag, this.impl);
+    }
+}

src/helpers/index.ts

@@ -0,0 +1,30 @@
+import { DateAndTimeUtils } from "../utils/dateAndTime";
+import { HelperConstructorBlock } from "./helper";
+import { HelperContext } from "./context";
+
+import { customDatetimeHelper } from "./custom_datetime";
+import { compareHelper } from "./compare";
+import { mathHelper } from "./math";
+import { conditionHelper } from "./condition";
+import { repeatHelper } from "./repeat";
+import { datetimeHelper } from "./datetime";
+import { caseHelper } from "./case";
+
+export class HelperFactory {
+    private static helpers: HelperConstructorBlock[] = [
+        customDatetimeHelper,
+        compareHelper,
+        mathHelper,
+        conditionHelper,
+        repeatHelper,
+        datetimeHelper,
+        caseHelper,
+    ];
+
+    static registerHelpers(dateAndTimeUtils: DateAndTimeUtils): void {
+        const context = new HelperContext(dateAndTimeUtils);
+        for (const helper of this.helpers) {
+            helper(context).register();
+        }
+    }
+}

src/helpers/math.ts

@@ -0,0 +1,30 @@
+import { HandlebarsHelper, HelperConstructorBlock } from "./helper";
+
+export const mathHelper: HelperConstructorBlock = ctx => {
+    return new HandlebarsHelper("math", (rawV1, operator, rawV2): number => {
+        const v1 = Number.parseFloat(rawV1);
+        const v2 = Number.parseFloat(rawV2);
+
+        if (Number.isNaN(v1) || Number.isNaN(v2)) {
+            throw new Error(`Can't convert "${rawV1}" and "${rawV2}" to numbers while using math`);
+        }
+
+        switch (operator) {
+            case "+":
+                return v1 + v2;
+            case "-":
+                return v1 - v2;
+            case "*":
+                return v1 * v2;
+            case "/":
+                return v1 / v2;
+            case "**":
+                return v1 ** v2;
+            case "%":
+                if (!v2) throw new Error("% operator used with 0");
+                return v1 % v2;
+            default:
+                throw new Error(`Invalid operator used with math: ${operator}`);
+        }
+    });
+};

src/helpers/repeat.ts

@@ -0,0 +1,17 @@
+import { HandlebarsHelper, HelperConstructorBlock } from "./helper";
+
+export const repeatHelper: HelperConstructorBlock = (ctx) => {
+    return new HandlebarsHelper("repeat", function (rawNum, options) {
+        const num = Number.parseInt(rawNum);
+
+        if (Number.isNaN(num)) {
+            throw new Error(`Can't convert "${rawNum}" to number while using repeat`);
+        }
+
+        let ret = "";
+        for (let i = 0; i < rawNum; i++) {
+            ret += options.fn({ ...this, "repeat_index": i });
+        }
+        return ret;
+    });
+};

src/helpers/utils/attributes.ts

@@ -0,0 +1,57 @@
+export enum AttributeValueType {
+    Number = "number",
+    String = "string",
+    Boolean = "boolean",
+}
+
+export interface AttributeDefinition {
+    name: string;
+    valueType: AttributeValueType;
+    defaultValue: unknown
+}
+
+interface RawAttributes {
+    [attr: string]: unknown
+}
+
+export interface ParsedAttributes {
+    [attr: string]: string | number | boolean
+}
+
+export class AttributeParser {
+    constructor(private schema: AttributeDefinition[]) {}
+
+    private parseAttribute(attr: AttributeDefinition, rawValue: unknown) {
+        switch (attr.valueType) {
+            case AttributeValueType.Boolean:
+                return !!rawValue;
+            case AttributeValueType.Number: {
+                const v = typeof rawValue === "string" ? Number.parseFloat(rawValue) : rawValue;
+                if (typeof v !== "number" || Number.isNaN(v)) {
+                    throw new Error(`Can't convert "${rawValue}" to number while parsing ${attr.name}.`);
+                }
+                return v;
+            }
+            case AttributeValueType.String:
+                return new String(rawValue).toString();
+        }
+    }
+
+    parse(rawAttributes: RawAttributes): ParsedAttributes {
+        const parsedAttributes = {};
+
+        if (!(typeof rawAttributes === "object")) {
+            throw new Error("There was an error parsing attributes.")
+        }
+
+        for (const attr of this.schema) {
+            if (attr.name in rawAttributes) {
+                parsedAttributes[attr.name] = this.parseAttribute(attr, rawAttributes[attr.name]);
+            } else {
+                parsedAttributes[attr.name] = attr.defaultValue;
+            }
+        }
+
+        return parsedAttributes;
+    }
+}

src/parser.ts

@@ -7,6 +7,7 @@ import { Note } from "./utils/templates";
 import { getVariableFromDefinition } from "./variables/parser";
 import { CustomVariable } from "./variables/types/base";
 import { setTemplateVariablesView } from "./views/templateVariables";
+import { HelperFactory } from "./helpers";
 
 // Can't use import for this library because the types in the library
 // are declared incorrectly which result in typescript errors.
@@ -38,10 +39,6 @@ export class Parser {
     }
 
     private getDefaultContext() {
-        Handlebars.registerHelper("custom_datetime", (options) => {
-            return this.utils.getCurrentTime(options.fn(this));
-        });
-
         return {
             date: this.utils.getCurrentTime(this.utils.getDateFormat()),
             time: this.utils.getCurrentTime(this.utils.getTimeFormat()),
@@ -231,6 +228,8 @@ export class Parser {
         template.body = this.preProcessTemplateBody(template.body);
 
         try {
+            HelperFactory.registerHelpers(this.utils);
+
             const processedTemplate = frontmatter(template.body);
             const templateVariables = processedTemplate.attributes;