1 files changed, 398 insertions, 0 deletions
diff --git a/src/lib/rx.ts b/src/lib/rx.ts
new file mode 100644
index 0000000..dbdd3ad
--- /dev/null
+++ b/src/lib/rx.ts
@@ -0,0 +1,398 @@
+// Html
+
+export interface Html {
+  type: 'Tag' | 'WithVar'
+}
+
+export interface Tag extends Html {
+  type: 'Tag'
+  tagName: string
+  attributes: Attributes
+  children?: Array<Child>
+  onmount?: (element: Element) => void
+  onunmount?: (element: Element) => void
+}
+
+export interface WithVar<A> extends Html {
+  type: 'WithVar'
+  init: A
+  getChildren: (v: Var<A>, update: (f: (value: A) => A) => void) => Child
+}
+
+interface Attributes {
+  [key: string]: Rx<AttributeValue> | AttributeValue
+}
+
+export type AttributeValue
+  = string
+  | number
+  | boolean
+  | ((event: Event) => void)
+  | ((element: Element) => void)
+
+export type Child = false | undefined | string | number | Html | Rx<Child> | Array<Child>
+
+function isChild(x: any): x is Child {
+  return (typeof x === 'string'
+    || typeof x === 'number'
+    || isHtml(x)
+    || isRx(x)
+    || Array.isArray(x))
+}
+
+type ValueOrArray<T> = T | Array<ValueOrArray<T>>
+
+export function h(
+  tagName: string,
+  x?: Attributes | Child,
+  ...children: Array<Child>
+): Tag {
+  if (x === undefined || x === false) {
+    return {
+      type: 'Tag',
+      tagName,
+      attributes: {}
+    }
+  } else if (isChild(x)) {
+    return {
+      type: 'Tag',
+      tagName,
+      attributes: {},
+      children: [x, ...children],
+    }
+  } else {
+    let attributes = x as Attributes
+    let onmount, onunmount
+    if ('onmount' in attributes) {
+      onmount = attributes['onmount'] as (element: Element) => void
+      delete attributes['onmount']
+    }
+    if ('onunmount' in attributes) {
+      onunmount = attributes['onunmount'] as (element: Element) => void
+      delete attributes['onunmount']
+    }
+    return {
+      type: 'Tag',
+      tagName,
+      attributes,
+      children,
+      onmount,
+      onunmount
+    }
+  }
+}
+
+export function withVar<A>(init: A, getChildren: (v: Var<A>, update: (f: (value: A) => A) => void) => Child): WithVar<A> {
+  return {
+    type: 'WithVar',
+    init,
+    getChildren
+  }
+}
+
+// Rx
+
+export type RxAble<A> = Rx<A> | A
+
+export class Rx<A> {
+  map<B>(f: (value: A) => B): Rx<B> {
+    return new Map<A, B>(this, f)
+  }
+
+  flatMap<B>(f: (value: A) => Rx<B>): Rx<B> {
+    return new FlatMap<A, B>(this, f)
+  }
+}
+
+class Var<A> extends Rx<A> {
+  readonly type: 'Var'
+  readonly id: string
+
+  constructor(id: string) {
+    super()
+    this.id = id
+    this.type = 'Var'
+  }
+}
+
+export class Map<A, B> extends Rx<B> {
+  readonly type: 'Map'
+  readonly rx: Rx<A>
+  readonly f: (value: A) => B
+
+  constructor(rx: Rx<A>, f: (value: A) => B) {
+    super()
+    this.type = 'Map'
+    this.rx = rx
+    this.f = f
+  }
+}
+
+export class FlatMap<A, B> extends Rx<B> {
+  readonly type: 'FlatMap'
+  readonly rx: Rx<A>
+  readonly f: (value: A) => Rx<B>
+
+  constructor(rx: Rx<A>, f: (value: A) => Rx<B>) {
+    super()
+    this.type = 'FlatMap'
+    this.rx = rx
+    this.f = f
+  }
+}
+
+// Mount
+
+export function mount(child: Child): Cancelable {
+  const state = new State()
+  let appendRes = appendChild(state, document.body, child)
+  return appendRes.cancel
+}
+
+interface StateEntry<A> {
+  value: A
+  subscribers: Array<(value: A) => void>
+}
+
+class State {
+  readonly state: {[key: string]: StateEntry<any>}
+  varCounter: bigint
+
+  constructor() {
+    this.state = {}
+    this.varCounter = BigInt(0)
+  }
+
+  register<A>(initValue: A) {
+    const v = new Var(this.varCounter.toString())
+    this.varCounter += BigInt(1)
+    this.state[v.id] = {
+      value: initValue,
+      subscribers: []
+    }
+    return v
+  }
+
+  unregister<A>(v: Var<A>) {
+    delete this.state[v.id]
+  }
+
+  get<A>(v: Var<A>) {
+    return this.state[v.id].value
+  }
+
+  update<A>(v: Var<A>, f: (value: A) => A) {
+    const value = f(this.state[v.id].value)
+    this.state[v.id].value = value
+    this.state[v.id].subscribers.forEach(notify => {
+      // Don’t notify if it has been removed from a precedent notifier
+      if (this.state[v.id].subscribers.indexOf(notify) !== -1) {
+        notify(value)
+      }
+    })
+  }
+
+  subscribe<A>(v: Var<A>, notify: (value: A) => void): Cancelable {
+    this.state[v.id].subscribers.push(notify)
+    return () => this.state[v.id].subscribers = this.state[v.id].subscribers.filter(n => n !== notify)
+  }
+}
+
+// Cancelable
+
+type Cancelable = () => void
+
+const voidCancel = () => {}
+
+// Removable
+
+type Removable = () => void
+
+const voidRemove = () => {}
+
+// Rx run
+
+function rxRun<A>(state: State, rx: Rx<A>, effect: (value: A) => void): Cancelable {
+  if (isVar(rx)) {
+    const cancel = state.subscribe(rx, effect)
+    effect(state.get(rx))
+    return cancel
+  } else if (isMap<A, any>(rx)) {
+    return rxRun(state, rx.rx, value => effect(rx.f(value)))
+  } else if (isFlatMap(rx)) {
+    let cancel1 = voidCancel
+    const cancel2 = rxRun(state, rx.rx, (value: A) => {
+      cancel1()
+      cancel1 = rxRun(state, rx.f(value), effect)
+    })
+    return () => {
+      cancel2()
+      cancel1()
+    }
+  } else {
+    throw new Error(`Unrecognized rx: ${rx}`)
+  }
+}
+
+function isRx<A>(x: any): x is Rx<A> {
+  return x !== undefined && x.type !== undefined && (x.type === "Var" || x.type === "Map" || x.type === "FlatMap")
+}
+
+function isVar<A>(x: any): x is Var<A> {
+  return x.type === "Var"
+}
+
+function isMap<A, B>(x: any): x is Map<A, B> {
+    return x.type === "Map"
+}
+
+function isFlatMap<A, B>(x: any): x is FlatMap<A, B> {
+    return x.type === "FlatMap"
+}
+
+// Append
+
+interface AppendResult {
+  cancel: Cancelable
+  remove: Removable
+  lastAdded?: Node
+}
+
+function appendChild(state: State, element: Element, child: Child, lastAdded?: Node): AppendResult {
+  if (Array.isArray(child)) {
+    let cancels: Array<Cancelable> = []
+    let removes: Array<Removable> = []
+    child.forEach((o) => {
+      const appendResult = appendChild(state, element, o, lastAdded)
+      cancels.push(appendResult.cancel)
+      removes.push(appendResult.remove)
+      lastAdded = appendResult.lastAdded
+    })
+    return {
+      cancel: () => cancels.forEach((o) => o()),
+      remove: () => removes.forEach((o) => o()),
+      lastAdded
+    }
+  } else if (typeof child == "string") {
+    const node = document.createTextNode(child)
+    appendNode(element, node, lastAdded)
+    return {
+      cancel: voidCancel,
+      remove: () => element.removeChild(node),
+      lastAdded: node
+    }
+  } else if (typeof child == "number") {
+    return appendChild(state, element, child.toString(), lastAdded)
+  } else if (isTag(child)) {
+    const { tagName, attributes, children, onmount, onunmount } = child
+
+    const childElement = document.createElement(tagName)
+    const cancelAttributes = Object.entries(attributes).map(([key, value]) => {
+      if (isRx<AttributeValue>(value)) {
+        return rxRun(state, value, newValue => setAttribute(state, childElement, key, newValue))
+      } else {
+        setAttribute(state, childElement, key, value)
+      }
+    })
+
+    const appendChildrenRes = appendChild(state, childElement, children)
+
+    appendNode(element, childElement, lastAdded)
+
+    if (onmount !== undefined) {
+      onmount(childElement)
+    }
+
+    return {
+      cancel: () => {
+        cancelAttributes.forEach(cancel => cancel !== undefined ? cancel() : {})
+        appendChildrenRes.cancel()
+        if (onunmount !== undefined) {
+          onunmount(childElement)
+        }
+      },
+      remove: () => element.removeChild(childElement),
+      lastAdded: childElement,
+    }
+  } else if (isWithVar(child)) {
+    const { init, getChildren } = child
+    const v = state.register(init)
+    const children = getChildren(v, f => state.update(v, f))
+    const appendRes = appendChild(state, element, children)
+    return {
+      cancel: () => {
+        appendRes.cancel()
+        state.unregister(v)
+      },
+      remove: () => appendRes.remove(),
+      lastAdded: appendRes.lastAdded
+    }
+  } else if (isRx(child)) {
+    const rxBase = document.createTextNode("")
+    element.append(rxBase)
+    let appendRes: AppendResult = {
+      cancel: voidCancel,
+      remove: voidRemove,
+      lastAdded: rxBase
+    }
+    const cancelRx = rxRun(state, child, (value: Child) => {
+      appendRes.cancel()
+      appendRes.remove()
+      appendRes = appendChild(state, element, value, rxBase)
+    })
+    return {
+      cancel: () => {
+        appendRes.cancel()
+        cancelRx()
+      },
+      remove: appendRes.remove,
+      lastAdded: appendRes.lastAdded,
+    }
+  } else if (child === undefined || child === false) {
+    return {
+      cancel: voidCancel,
+      remove: voidRemove,
+      lastAdded
+    }
+  } else {
+    throw new Error(`Unrecognized child: ${child}`)
+  }
+}
+
+function isHtml<A>(x: any): x is Html {
+  return isTag<A>(x) || isWithVar<A>(x)
+}
+
+function isTag<A>(x: any): x is Tag {
+  return x !== undefined && x.type === "Tag"
+}
+
+function isWithVar<A>(x: any): x is WithVar<A> {
+  return x !== undefined && x.type === "WithVar"
+}
+
+function appendNode(base: Element, node: Node, lastAdded?: Node) {
+  if (lastAdded !== undefined) {
+    base.insertBefore(node, lastAdded.nextSibling)
+  } else {
+    base.append(node)
+  }
+}
+
+function setAttribute(state: State, element: Element, key: string, attribute: AttributeValue) {
+  if (typeof attribute == "boolean") {
+    if (attribute) {
+      // @ts-ignore
+      element[key] = "true"
+    }
+  } else if (typeof attribute == "number") {
+    // @ts-ignore
+    element[key] = attribute.toString()
+  } else if (typeof attribute == "string") {
+    // @ts-ignore
+    element[key] = attribute
+  } else {
+    // @ts-ignore
+    element[key] = (event: Event) => attribute(event)
+  }
+}