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Diffstat (limited to 'src/thing/cacheable-object.js')
| -rw-r--r-- | src/thing/cacheable-object.js | 305 |
1 files changed, 0 insertions, 305 deletions
diff --git a/src/thing/cacheable-object.js b/src/thing/cacheable-object.js deleted file mode 100644 index 9af4160..0000000 --- a/src/thing/cacheable-object.js +++ /dev/null @@ -1,305 +0,0 @@ -// Generally extendable class for caching properties and handling dependencies, -// with a few key properties: -// -// 1) The behavior of every property is defined by its descriptor, which is a -// static value stored on the subclass (all instances share the same property -// descriptors). -// -// 1a) Additional properties may not be added past the time of object -// construction, and attempts to do so (including externally setting a -// property name which has no corresponding descriptor) will throw a -// TypeError. (This is done via an Object.seal(this) call after a newly -// created instance defines its own properties according to the descriptor -// on its constructor class.) -// -// 2) Properties may have two flags set: update and expose. Properties which -// update are provided values from the external. Properties which expose -// provide values to the external, generally dependent on other update -// properties (within the same object). -// -// 2a) Properties may be flagged as both updating and exposing. This is so -// that the same name may be used for both "output" and "input". -// -// 3) Exposed properties have values which are computations dependent on other -// properties, as described by a `compute` function on the descriptor. -// Depended-upon properties are explicitly listed on the descriptor next to -// this function, and are only provided as arguments to the function once -// listed. -// -// 3a) An exposed property may depend only upon updating properties, not other -// exposed properties (within the same object). This is to force the -// general complexity of a single object to be fairly simple: inputs -// directly determine outputs, with the only in-between step being the -// `compute` function, no multiple-layer dependencies. Note that this is -// only true within a given object - externally, values provided to one -// object's `update` may be (and regularly are) the exposed values of -// another object. -// -// 3b) If a property both updates and exposes, it is automatically regarded as -// a dependancy. (That is, its exposed value will depend on the value it is -// updated with.) Rather than a required `compute` function, these have an -// optional `transform` function, which takes the update value as its first -// argument and then the usual key-value dependencies as its second. If no -// `transform` function is provided, the expose value is the same as the -// update value. -// -// 4) Exposed properties are cached; that is, if no depended-upon properties are -// updated, the value of an exposed property is not recomputed. -// -// 4a) The cache for an exposed property is invalidated as soon as any of its -// dependencies are updated, but the cache itself is lazy: the exposed -// value will not be recomputed until it is again accessed. (Likewise, an -// exposed value won't be computed for the first time until it is first -// accessed.) -// -// 5) Updating a property may optionally apply validation checks before passing, -// declared by a `validate` function on the `update` block. This function -// should either throw an error (e.g. TypeError) or return false if the value -// is invalid. -// -// 6) Objects do not expect all updating properties to be provided at once. -// Incomplete objects are deliberately supported and enabled. -// -// 6a) The default value for every updating property is null; undefined is not -// accepted as a property value under any circumstances (it always errors). -// However, this default may be overridden by specifying a `default` value -// on a property's `update` block. (This value will be checked against -// the property's validate function.) Note that a property may always be -// updated to null, even if the default is non-null. (Null always bypasses -// the validate check.) -// -// 6b) It's required by the external consumer of an object to determine whether -// or not the object is ready for use (within the larger program). This is -// convenienced by the static CacheableObject.listAccessibleProperties() -// function, which provides a mapping of exposed property names to whether -// or not their dependencies are yet met. - -import { color, ENABLE_COLOR } from '../util/cli.js'; - -import { inspect as nodeInspect } from 'util'; - -function inspect(value) { - return nodeInspect(value, {colors: ENABLE_COLOR}); -} - -export default class CacheableObject { - static instance = Symbol('CacheableObject `this` instance'); - - #propertyUpdateValues = Object.create(null); - #propertyUpdateCacheInvalidators = Object.create(null); - - /* - // Note the constructor doesn't take an initial data source. Due to a quirk - // of JavaScript, private members can't be accessed before the superclass's - // constructor is finished processing - so if we call the overridden - // update() function from inside this constructor, it will error when - // writing to private members. Pretty bad! - // - // That means initial data must be provided by following up with update() - // after constructing the new instance of the Thing (sub)class. - */ - - constructor() { - this.#defineProperties(); - this.#initializeUpdatingPropertyValues(); - - if (CacheableObject.DEBUG_SLOW_TRACK_INVALID_PROPERTIES) { - return new Proxy(this, { - get: (obj, key) => { - if (!Object.hasOwn(obj, key)) { - if (key !== 'constructor') { - CacheableObject._invalidAccesses.add(`(${obj.constructor.name}).${key}`); - } - } - return obj[key]; - } - }); - } - } - - #initializeUpdatingPropertyValues() { - for (const [ property, descriptor ] of Object.entries(this.constructor.propertyDescriptors)) { - const { flags, update } = descriptor; - - if (!flags.update) { - continue; - } - - if (update?.default) { - this[property] = update?.default; - } else { - this[property] = null; - } - } - } - - #defineProperties() { - for (const [ property, descriptor ] of Object.entries(this.constructor.propertyDescriptors)) { - const { flags } = descriptor; - - const definition = { - configurable: false, - enumerable: true - }; - - if (flags.update) { - definition.set = this.#getUpdateObjectDefinitionSetterFunction(property); - } - - if (flags.expose) { - definition.get = this.#getExposeObjectDefinitionGetterFunction(property); - } - - Object.defineProperty(this, property, definition); - } - - Object.seal(this); - } - - #getUpdateObjectDefinitionSetterFunction(property) { - const { update } = this.#getPropertyDescriptor(property); - const validate = update?.validate; - const allowNull = update?.allowNull; - - return (newValue) => { - const oldValue = this.#propertyUpdateValues[property]; - - if (newValue === undefined) { - throw new ValueError(`Properties cannot be set to undefined`); - } - - if (newValue === oldValue) { - return; - } - - if (newValue !== null && validate) { - try { - const result = validate(newValue); - if (result === undefined) { - throw new TypeError(`Validate function returned undefined`); - } else if (result !== true) { - throw new TypeError(`Validation failed for value ${newValue}`); - } - } catch (error) { - error.message = `Property ${color.green(property)} (${inspect(this[property])} -> ${inspect(newValue)}): ${error.message}`; - throw error; - } - } - - this.#propertyUpdateValues[property] = newValue; - this.#invalidateCachesDependentUpon(property); - }; - } - - #getUpdatePropertyValidateFunction(property) { - const descriptor = this.#getPropertyDescriptor(property); - } - - #getPropertyDescriptor(property) { - return this.constructor.propertyDescriptors[property]; - } - - #invalidateCachesDependentUpon(property) { - for (const invalidate of this.#propertyUpdateCacheInvalidators[property] || []) { - invalidate(); - } - } - - #getExposeObjectDefinitionGetterFunction(property) { - const { flags } = this.#getPropertyDescriptor(property); - const compute = this.#getExposeComputeFunction(property); - - if (compute) { - let cachedValue; - const checkCacheValid = this.#getExposeCheckCacheValidFunction(property); - return () => { - if (checkCacheValid()) { - return cachedValue; - } else { - return (cachedValue = compute()); - } - }; - } else if (!flags.update && !compute) { - throw new Error(`Exposed property ${property} does not update and is missing compute function`); - } else { - return () => this.#propertyUpdateValues[property]; - } - } - - #getExposeComputeFunction(property) { - const { flags, expose } = this.#getPropertyDescriptor(property); - - const compute = expose?.compute; - const transform = expose?.transform; - - if (flags.update && !transform) { - return null; - } else if (flags.update && compute) { - throw new Error(`Updating property ${property} has compute function, should be formatted as transform`); - } else if (!flags.update && !compute) { - throw new Error(`Exposed property ${property} does not update and is missing compute function`); - } - - const dependencyKeys = expose.dependencies || []; - const dependencyGetters = dependencyKeys.map(key => () => [key, this.#propertyUpdateValues[key]]); - const getAllDependencies = () => Object.fromEntries(dependencyGetters.map(f => f()) - .concat([[this.constructor.instance, this]])); - - if (flags.update) { - return () => transform(this.#propertyUpdateValues[property], getAllDependencies()); - } else { - return () => compute(getAllDependencies()); - } - } - - #getExposeCheckCacheValidFunction(property) { - const { flags, expose } = this.#getPropertyDescriptor(property); - - let valid = false; - - const invalidate = () => { - valid = false; - }; - - const dependencyKeys = new Set(expose?.dependencies); - - if (flags.update) { - dependencyKeys.add(property); - } - - for (const key of dependencyKeys) { - if (this.#propertyUpdateCacheInvalidators[key]) { - this.#propertyUpdateCacheInvalidators[key].push(invalidate); - } else { - this.#propertyUpdateCacheInvalidators[key] = [invalidate]; - } - } - - return () => { - if (!valid) { - valid = true; - return false; - } else { - return true; - } - }; - } - - static DEBUG_SLOW_TRACK_INVALID_PROPERTIES = false; - static _invalidAccesses = new Set(); - - static showInvalidAccesses() { - if (!this.DEBUG_SLOW_TRACK_INVALID_PROPERTIES) { - return; - } - - if (!this._invalidAccesses.size) { - return; - } - - console.log(`${this._invalidAccesses.size} unique invalid accesses:`); - for (const line of this._invalidAccesses) { - console.log(` - ${line}`); - } - } -} |