@tanstack/db
Version:
A reactive client store for building super fast apps on sync
924 lines (818 loc) • 32.1 kB
text/typescript
/**
* A utility for creating a proxy that captures changes to an object
* and provides a way to retrieve those changes.
*/
import { deepEquals, isTemporal } from "./utils"
/**
* Simple debug utility that only logs when debug mode is enabled
* Set DEBUG to true in localStorage to enable debug logging
*/
function debugLog(...args: Array<unknown>): void {
// Check if we're in a browser environment
const isBrowser =
typeof window !== `undefined` && typeof localStorage !== `undefined`
// In browser, check localStorage for debug flag
if (isBrowser && localStorage.getItem(`DEBUG`) === `true`) {
console.log(`[proxy]`, ...args)
}
// In Node.js environment, check for environment variable (though this is primarily for browser)
else if (
// true
!isBrowser &&
typeof process !== `undefined` &&
process.env.DEBUG === `true`
) {
console.log(`[proxy]`, ...args)
}
}
// Add TypedArray interface with proper type
interface TypedArray {
length: number
[index: number]: number
}
// Update type for ChangeTracker
interface ChangeTracker<T extends object> {
originalObject: T
modified: boolean
copy_: T
proxyCount: number
assigned_: Record<string | symbol, boolean>
parent?:
| {
tracker: ChangeTracker<Record<string | symbol, unknown>>
prop: string | symbol
}
| {
tracker: ChangeTracker<Record<string | symbol, unknown>>
prop: string | symbol
updateMap: (newValue: unknown) => void
}
| {
tracker: ChangeTracker<Record<string | symbol, unknown>>
prop: unknown
updateSet: (newValue: unknown) => void
}
target: T
}
/**
* Deep clones an object while preserving special types like Date and RegExp
*/
function deepClone<T extends unknown>(
obj: T,
visited = new WeakMap<object, unknown>()
): T {
// Handle null and undefined
if (obj === null || obj === undefined) {
return obj
}
// Handle primitive types
if (typeof obj !== `object`) {
return obj
}
// If we've already cloned this object, return the cached clone
if (visited.has(obj as object)) {
return visited.get(obj as object) as T
}
if (obj instanceof Date) {
return new Date(obj.getTime()) as unknown as T
}
if (obj instanceof RegExp) {
return new RegExp(obj.source, obj.flags) as unknown as T
}
if (Array.isArray(obj)) {
const arrayClone = [] as Array<unknown>
visited.set(obj as object, arrayClone)
obj.forEach((item, index) => {
arrayClone[index] = deepClone(item, visited)
})
return arrayClone as unknown as T
}
// Handle TypedArrays
if (ArrayBuffer.isView(obj) && !(obj instanceof DataView)) {
// Get the constructor to create a new instance of the same type
const TypedArrayConstructor = Object.getPrototypeOf(obj).constructor
const clone = new TypedArrayConstructor(
(obj as unknown as TypedArray).length
) as unknown as TypedArray
visited.set(obj as object, clone)
// Copy the values
for (let i = 0; i < (obj as unknown as TypedArray).length; i++) {
clone[i] = (obj as unknown as TypedArray)[i]!
}
return clone as unknown as T
}
if (obj instanceof Map) {
const clone = new Map() as Map<unknown, unknown>
visited.set(obj as object, clone)
obj.forEach((value, key) => {
clone.set(key, deepClone(value, visited))
})
return clone as unknown as T
}
if (obj instanceof Set) {
const clone = new Set()
visited.set(obj as object, clone)
obj.forEach((value) => {
clone.add(deepClone(value, visited))
})
return clone as unknown as T
}
// Handle Temporal objects
if (isTemporal(obj)) {
// Temporal objects are immutable, so we can return them directly
// This preserves all their internal state correctly
return obj
}
const clone = {} as Record<string | symbol, unknown>
visited.set(obj as object, clone)
for (const key in obj) {
if (Object.prototype.hasOwnProperty.call(obj, key)) {
clone[key] = deepClone(
(obj as Record<string | symbol, unknown>)[key],
visited
)
}
}
const symbolProps = Object.getOwnPropertySymbols(obj)
for (const sym of symbolProps) {
clone[sym] = deepClone(
(obj as Record<string | symbol, unknown>)[sym],
visited
)
}
return clone as T
}
let count = 0
function getProxyCount() {
count += 1
return count
}
/**
* Creates a proxy that tracks changes to the target object
*
* @param target The object to proxy
* @param parent Optional parent information
* @returns An object containing the proxy and a function to get the changes
*/
export function createChangeProxy<
T extends Record<string | symbol, any | undefined>,
>(
target: T,
parent?: {
tracker: ChangeTracker<Record<string | symbol, unknown>>
prop: string | symbol
}
): {
proxy: T
getChanges: () => Record<string | symbol, any>
} {
const changeProxyCache = new Map<object, object>()
function memoizedCreateChangeProxy<
TInner extends Record<string | symbol, any | undefined>,
>(
innerTarget: TInner,
innerParent?: {
tracker: ChangeTracker<Record<string | symbol, unknown>>
prop: string | symbol
}
): {
proxy: TInner
getChanges: () => Record<string | symbol, any>
} {
debugLog(`Object ID:`, innerTarget.constructor.name)
if (changeProxyCache.has(innerTarget)) {
return changeProxyCache.get(innerTarget) as {
proxy: TInner
getChanges: () => Record<string | symbol, any>
}
} else {
const changeProxy = createChangeProxy(innerTarget, innerParent)
changeProxyCache.set(innerTarget, changeProxy)
return changeProxy
}
}
// Create a WeakMap to cache proxies for nested objects
// This prevents creating multiple proxies for the same object
// and handles circular references
const proxyCache = new Map<object, object>()
// Create a change tracker to track changes to the object
const changeTracker: ChangeTracker<T> = {
copy_: deepClone(target),
originalObject: deepClone(target),
proxyCount: getProxyCount(),
modified: false,
assigned_: {},
parent,
target, // Store reference to the target object
}
debugLog(
`createChangeProxy called for target`,
target,
changeTracker.proxyCount
)
// Mark this object and all its ancestors as modified
// Also propagate the actual changes up the chain
function markChanged(state: ChangeTracker<object>) {
if (!state.modified) {
state.modified = true
}
// Propagate the change up the parent chain
if (state.parent) {
debugLog(`propagating change to parent`)
// Check if this is a special Map parent with updateMap function
if (`updateMap` in state.parent) {
// Use the special updateMap function for Maps
state.parent.updateMap(state.copy_)
} else if (`updateSet` in state.parent) {
// Use the special updateSet function for Sets
state.parent.updateSet(state.copy_)
} else {
// Update parent's copy with this object's current state
state.parent.tracker.copy_[state.parent.prop] = state.copy_
state.parent.tracker.assigned_[state.parent.prop] = true
}
// Mark parent as changed
markChanged(state.parent.tracker)
}
}
// Check if all properties in the current state have reverted to original values
function checkIfReverted(
state: ChangeTracker<Record<string | symbol, unknown>>
): boolean {
debugLog(
`checkIfReverted called with assigned keys:`,
Object.keys(state.assigned_)
)
// If there are no assigned properties, object is unchanged
if (
Object.keys(state.assigned_).length === 0 &&
Object.getOwnPropertySymbols(state.assigned_).length === 0
) {
debugLog(`No assigned properties, returning true`)
return true
}
// Check each assigned regular property
for (const prop in state.assigned_) {
// If this property is marked as assigned
if (state.assigned_[prop] === true) {
const currentValue = state.copy_[prop]
const originalValue = (state.originalObject as any)[prop]
debugLog(
`Checking property ${String(prop)}, current:`,
currentValue,
`original:`,
originalValue
)
// If the value is not equal to original, something is still changed
if (!deepEquals(currentValue, originalValue)) {
debugLog(`Property ${String(prop)} is different, returning false`)
return false
}
} else if (state.assigned_[prop] === false) {
// Property was deleted, so it's different from original
debugLog(`Property ${String(prop)} was deleted, returning false`)
return false
}
}
// Check each assigned symbol property
const symbolProps = Object.getOwnPropertySymbols(state.assigned_)
for (const sym of symbolProps) {
if (state.assigned_[sym] === true) {
const currentValue = (state.copy_ as any)[sym]
const originalValue = (state.originalObject as any)[sym]
// If the value is not equal to original, something is still changed
if (!deepEquals(currentValue, originalValue)) {
debugLog(`Symbol property is different, returning false`)
return false
}
} else if (state.assigned_[sym] === false) {
// Property was deleted, so it's different from original
debugLog(`Symbol property was deleted, returning false`)
return false
}
}
debugLog(`All properties match original values, returning true`)
// All assigned properties match their original values
return true
}
// Update parent status based on child changes
function checkParentStatus(
parentState: ChangeTracker<Record<string | symbol, unknown>>,
childProp: string | symbol | unknown
) {
debugLog(`checkParentStatus called for child prop:`, childProp)
// Check if all properties of the parent are reverted
const isReverted = checkIfReverted(parentState)
debugLog(`Parent checkIfReverted returned:`, isReverted)
if (isReverted) {
debugLog(`Parent is fully reverted, clearing tracking`)
// If everything is reverted, clear the tracking
parentState.modified = false
parentState.assigned_ = {}
// Continue up the chain
if (parentState.parent) {
debugLog(`Continuing up the parent chain`)
checkParentStatus(parentState.parent.tracker, parentState.parent.prop)
}
}
}
// Create a proxy for the target object
function createObjectProxy<TObj extends object>(obj: TObj): TObj {
debugLog(`createObjectProxy`, obj)
// If we've already created a proxy for this object, return it
if (proxyCache.has(obj)) {
debugLog(`proxyCache found match`)
return proxyCache.get(obj) as TObj
}
// Create a proxy for the object
const proxy = new Proxy(obj, {
get(ptarget, prop) {
debugLog(`get`, ptarget, prop)
const value =
changeTracker.copy_[prop as keyof T] ??
changeTracker.originalObject[prop as keyof T]
const originalValue = changeTracker.originalObject[prop as keyof T]
debugLog(`value (at top of proxy get)`, value)
// If it's a getter, return the value directly
const desc = Object.getOwnPropertyDescriptor(ptarget, prop)
if (desc?.get) {
return value
}
// If the value is a function, bind it to the ptarget
if (typeof value === `function`) {
// For Array methods that modify the array
if (Array.isArray(ptarget)) {
const methodName = prop.toString()
const modifyingMethods = new Set([
`pop`,
`push`,
`shift`,
`unshift`,
`splice`,
`sort`,
`reverse`,
`fill`,
`copyWithin`,
])
if (modifyingMethods.has(methodName)) {
return function (...args: Array<unknown>) {
const result = value.apply(changeTracker.copy_, args)
markChanged(changeTracker)
return result
}
}
}
// For Map and Set methods that modify the collection
if (ptarget instanceof Map || ptarget instanceof Set) {
const methodName = prop.toString()
const modifyingMethods = new Set([
`set`,
`delete`,
`clear`,
`add`,
`pop`,
`push`,
`shift`,
`unshift`,
`splice`,
`sort`,
`reverse`,
])
if (modifyingMethods.has(methodName)) {
return function (...args: Array<unknown>) {
const result = value.apply(changeTracker.copy_, args)
markChanged(changeTracker)
return result
}
}
// Handle iterator methods for Map and Set
const iteratorMethods = new Set([
`entries`,
`keys`,
`values`,
`forEach`,
Symbol.iterator,
])
if (iteratorMethods.has(methodName) || prop === Symbol.iterator) {
return function (this: unknown, ...args: Array<unknown>) {
const result = value.apply(changeTracker.copy_, args)
// For forEach, we need to wrap the callback to track changes
if (methodName === `forEach`) {
const callback = args[0]
if (typeof callback === `function`) {
// Replace the original callback with our wrapped version
const wrappedCallback = function (
this: unknown,
// eslint-disable-next-line
value: unknown,
key: unknown,
collection: unknown
) {
// Call the original callback
const cbresult = callback.call(
this,
value,
key,
collection
)
// Mark as changed since the callback might have modified the value
markChanged(changeTracker)
return cbresult
}
// Call forEach with our wrapped callback
return value.apply(ptarget, [
wrappedCallback,
...args.slice(1),
])
}
}
// For iterators (entries, keys, values, Symbol.iterator)
if (
methodName === `entries` ||
methodName === `values` ||
methodName === Symbol.iterator.toString() ||
prop === Symbol.iterator
) {
// If it's an iterator, we need to wrap the returned iterator
// to track changes when the values are accessed and potentially modified
const originalIterator = result
// For values() iterator on Maps, we need to create a value-to-key mapping
const valueToKeyMap = new Map()
if (methodName === `values` && ptarget instanceof Map) {
// Build a mapping from value to key for reverse lookup
// Use the copy_ (which is the current state) to build the mapping
for (const [
key,
mapValue,
] of changeTracker.copy_.entries()) {
valueToKeyMap.set(mapValue, key)
}
}
// For Set iterators, we need to create an original-to-modified mapping
const originalToModifiedMap = new Map()
if (ptarget instanceof Set) {
// Initialize with original values
for (const setValue of changeTracker.copy_.values()) {
originalToModifiedMap.set(setValue, setValue)
}
}
// Create a proxy for the iterator that will mark changes when next() is called
return {
next() {
const nextResult = originalIterator.next()
// If we have a value and it's an object, we need to track it
if (
!nextResult.done &&
nextResult.value &&
typeof nextResult.value === `object`
) {
// For entries, the value is a [key, value] pair
if (
methodName === `entries` &&
Array.isArray(nextResult.value) &&
nextResult.value.length === 2
) {
// The value is at index 1 in the [key, value] pair
if (
nextResult.value[1] &&
typeof nextResult.value[1] === `object`
) {
const mapKey = nextResult.value[0]
// Create a special parent tracker that knows how to update the Map
const mapParent = {
tracker: changeTracker,
prop: mapKey,
updateMap: (newValue: unknown) => {
// Update the Map in the copy
if (changeTracker.copy_ instanceof Map) {
changeTracker.copy_.set(mapKey, newValue)
}
},
}
// Create a proxy for the value and replace it in the result
const { proxy: valueProxy } =
memoizedCreateChangeProxy(
nextResult.value[1],
mapParent
)
nextResult.value[1] = valueProxy
}
} else if (
methodName === `values` ||
methodName === Symbol.iterator.toString() ||
prop === Symbol.iterator
) {
// If the value is an object, create a proxy for it
if (
typeof nextResult.value === `object` &&
nextResult.value !== null
) {
// For Map values(), try to find the key using our mapping
if (
methodName === `values` &&
ptarget instanceof Map
) {
const mapKey = valueToKeyMap.get(nextResult.value)
if (mapKey !== undefined) {
// Create a special parent tracker for this Map value
const mapParent = {
tracker: changeTracker,
prop: mapKey,
updateMap: (newValue: unknown) => {
// Update the Map in the copy
if (changeTracker.copy_ instanceof Map) {
changeTracker.copy_.set(mapKey, newValue)
}
},
}
const { proxy: valueProxy } =
memoizedCreateChangeProxy(
nextResult.value,
mapParent
)
nextResult.value = valueProxy
}
} else if (ptarget instanceof Set) {
// For Set, we need to track modifications and update the Set accordingly
const setOriginalValue = nextResult.value
const setParent = {
tracker: changeTracker,
prop: setOriginalValue, // Use the original value as the prop
updateSet: (newValue: unknown) => {
// Update the Set in the copy by removing old value and adding new one
if (changeTracker.copy_ instanceof Set) {
changeTracker.copy_.delete(setOriginalValue)
changeTracker.copy_.add(newValue)
// Update our mapping for future iterations
originalToModifiedMap.set(
setOriginalValue,
newValue
)
}
},
}
const { proxy: valueProxy } =
memoizedCreateChangeProxy(
nextResult.value,
setParent
)
nextResult.value = valueProxy
} else {
// For other cases, use a symbol as a placeholder
const tempKey = Symbol(`iterator-value`)
const { proxy: valueProxy } =
memoizedCreateChangeProxy(nextResult.value, {
tracker: changeTracker,
prop: tempKey,
})
nextResult.value = valueProxy
}
}
}
}
return nextResult
},
[Symbol.iterator]() {
return this
},
}
}
return result
}
}
}
return value.bind(ptarget)
}
// If the value is an object (but not Date, RegExp, or Temporal), create a proxy for it
if (
value &&
typeof value === `object` &&
!((value as any) instanceof Date) &&
!((value as any) instanceof RegExp) &&
!isTemporal(value)
) {
// Create a parent reference for the nested object
const nestedParent = {
tracker: changeTracker,
prop: String(prop),
}
// Create a proxy for the nested object
const { proxy: nestedProxy } = memoizedCreateChangeProxy(
originalValue,
nestedParent
)
// Cache the proxy
proxyCache.set(value, nestedProxy)
return nestedProxy
}
return value
},
set(_sobj, prop, value) {
const currentValue = changeTracker.copy_[prop as keyof T]
debugLog(
`set called for property ${String(prop)}, current:`,
currentValue,
`new:`,
value
)
// Only track the change if the value is actually different
if (!deepEquals(currentValue, value)) {
// Check if the new value is equal to the original value
// Important: Use the originalObject to get the true original value
const originalValue = changeTracker.originalObject[prop as keyof T]
const isRevertToOriginal = deepEquals(value, originalValue)
debugLog(
`value:`,
value,
`original:`,
originalValue,
`isRevertToOriginal:`,
isRevertToOriginal
)
if (isRevertToOriginal) {
debugLog(`Reverting property ${String(prop)} to original value`)
// If the value is reverted to its original state, remove it from changes
delete changeTracker.assigned_[prop.toString()]
// Make sure the copy is updated with the original value
debugLog(`Updating copy with original value for ${String(prop)}`)
changeTracker.copy_[prop as keyof T] = deepClone(originalValue)
// Check if all properties in this object have been reverted
debugLog(`Checking if all properties reverted`)
const allReverted = checkIfReverted(changeTracker)
debugLog(`All reverted:`, allReverted)
if (allReverted) {
debugLog(`All properties reverted, clearing tracking`)
// If all have been reverted, clear tracking
changeTracker.modified = false
changeTracker.assigned_ = {}
// If we're a nested object, check if the parent needs updating
if (parent) {
debugLog(`Updating parent for property:`, parent.prop)
checkParentStatus(parent.tracker, parent.prop)
}
} else {
// Some properties are still changed
debugLog(`Some properties still changed, keeping modified flag`)
changeTracker.modified = true
}
} else {
debugLog(`Setting new value for property ${String(prop)}`)
// Set the value on the copy
changeTracker.copy_[prop as keyof T] = value
// Track that this property was assigned - store using the actual property (symbol or string)
changeTracker.assigned_[prop.toString()] = true
// Mark this object and its ancestors as modified
debugLog(`Marking object and ancestors as modified`, changeTracker)
markChanged(changeTracker)
}
} else {
debugLog(`Value unchanged, not tracking`)
}
return true
},
defineProperty(_ptarget, prop, descriptor) {
// const result = Reflect.defineProperty(
// changeTracker.copy_,
// prop,
// descriptor
// )
// if (result) {
if (`value` in descriptor) {
changeTracker.copy_[prop as keyof T] = deepClone(descriptor.value)
changeTracker.assigned_[prop.toString()] = true
markChanged(changeTracker)
}
// }
// return result
return true
},
deleteProperty(dobj, prop) {
debugLog(`deleteProperty`, dobj, prop)
const stringProp = typeof prop === `symbol` ? prop.toString() : prop
if (stringProp in dobj) {
// Check if the property exists in the original object
const hadPropertyInOriginal =
stringProp in changeTracker.originalObject
// Delete the property from the copy
// Use type assertion to tell TypeScript this is allowed
delete (changeTracker.copy_ as Record<string | symbol, unknown>)[prop]
// If the property didn't exist in the original object, removing it
// should revert to the original state
if (!hadPropertyInOriginal) {
delete changeTracker.copy_[stringProp]
delete changeTracker.assigned_[stringProp]
// If this is the last change and we're not a nested object,
// mark the object as unmodified
if (
Object.keys(changeTracker.assigned_).length === 0 &&
Object.getOwnPropertySymbols(changeTracker.assigned_).length === 0
) {
changeTracker.modified = false
} else {
// We still have changes, keep as modified
changeTracker.modified = true
}
} else {
// Mark this property as deleted
changeTracker.assigned_[stringProp] = false
changeTracker.copy_[stringProp as keyof T] = undefined as T[keyof T]
markChanged(changeTracker)
}
}
return true
},
})
// Cache the proxy
proxyCache.set(obj, proxy)
return proxy
}
// Create a proxy for the target object
const proxy = createObjectProxy(target)
// Return the proxy and a function to get the changes
return {
proxy,
getChanges: () => {
debugLog(`getChanges called, modified:`, changeTracker.modified)
debugLog(changeTracker)
// First, check if the object is still considered modified
if (!changeTracker.modified) {
debugLog(`Object not modified, returning empty object`)
return {}
}
// If we have a copy, return it directly
// Check if valueObj is actually an object
if (
typeof changeTracker.copy_ !== `object` ||
Array.isArray(changeTracker.copy_)
) {
return changeTracker.copy_
}
if (Object.keys(changeTracker.assigned_).length === 0) {
return changeTracker.copy_
}
const result: Record<string, any | undefined> = {}
// Iterate through keys in keyObj
for (const key in changeTracker.copy_) {
// If the key's value is true and the key exists in valueObj
if (
changeTracker.assigned_[key] === true &&
key in changeTracker.copy_
) {
result[key] = changeTracker.copy_[key]
}
}
debugLog(`Returning copy:`, result)
return result as unknown as Record<string | symbol, unknown>
},
}
}
/**
* Creates proxies for an array of objects and tracks changes to each
*
* @param targets Array of objects to proxy
* @returns An object containing the array of proxies and a function to get all changes
*/
export function createArrayChangeProxy<T extends object>(
targets: Array<T>
): {
proxies: Array<T>
getChanges: () => Array<Record<string | symbol, unknown>>
} {
const proxiesWithChanges = targets.map((target) => createChangeProxy(target))
return {
proxies: proxiesWithChanges.map((p) => p.proxy),
getChanges: () => proxiesWithChanges.map((p) => p.getChanges()),
}
}
/**
* Creates a proxy for an object, passes it to a callback function,
* and returns the changes made by the callback
*
* @param target The object to proxy
* @param callback Function that receives the proxy and can make changes to it
* @returns The changes made to the object
*/
export function withChangeTracking<T extends object>(
target: T,
callback: (proxy: T) => void
): Record<string | symbol, unknown> {
const { proxy, getChanges } = createChangeProxy(target)
callback(proxy)
return getChanges()
}
/**
* Creates proxies for an array of objects, passes them to a callback function,
* and returns the changes made by the callback for each object
*
* @param targets Array of objects to proxy
* @param callback Function that receives the proxies and can make changes to them
* @returns Array of changes made to each object
*/
export function withArrayChangeTracking<T extends object>(
targets: Array<T>,
callback: (proxies: Array<T>) => void
): Array<Record<string | symbol, unknown>> {
const { proxies, getChanges } = createArrayChangeProxy(targets)
callback(proxies)
return getChanges()
}