Sanitization + better error reporting

src/assert.js

@@ -0,0 +1,51 @@
+const Point = require('./point')
+
+const assert = exports.assert = (exp, msg) => {
+    if (!exp) {
+        throw new Error(msg)
+    }
+}
+
+const type = exports.type = (val) => {
+    if (Array.isArray(val)) return 'array'
+    if (val === null) return 'null'
+    return typeof val
+}
+
+const sane = exports.sane = (val, name, _type) => {
+    assert(type(val) == _type, `Field "${name}" should be of type ${_type}!`)
+    return val
+}
+
+const detect_unexpected = exports.detect_unexpected = (obj, name, expected) => {
+    const sane_obj = sane(obj, name, 'object')
+    for (const key of Object.keys(sane_obj)) {
+        assert(expected.includes(key), `Unexpected key "${key}" within field "${name}"!`)
+    }
+}
+
+const xy = exports.xy = (raw, name) => {
+    assert(type(raw) == 'array' && raw.length == 2, `Field "${name}" should be an array of length 2!`)
+    const x = raw[0] || 0
+    const y = raw[1] || 0
+    assert(type(x) == 'number' && type(y) == 'number', `Field "${name}" should contain numbers!`)
+    return {x, y}
+}
+
+exports.anchor = (raw, name, points={}) => {
+    detect_unexpected(raw, name, ['ref', 'shift', 'rotate'])
+    let a = new Point()
+    if (raw.ref !== undefined) {
+        assert(points[raw.ref], `Unknown point reference "${raw.ref}" in anchor "${name}"!`)
+        a = points[raw.ref].clone()
+    }
+    if (raw.shift !== undefined) {
+        const xyval = xy(raw.shift, name + '.shift')
+        a.x += xyval.x
+        a.y += xyval.y
+    }
+    if (raw.rotate !== undefined) {
+        a.r += sane(raw.rotate || 0, name + '.rotate', 'number')
+    }
+    return a
+}