planning

node_modules/react-router/modules/miniCreateReactContext.js

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+// MIT License
+// Copyright (c) 2019-present StringEpsilon <StringEpsilon@gmail.com>
+// Copyright (c) 2017-2019 James Kyle <me@thejameskyle.com>
+// https://github.com/StringEpsilon/mini-create-react-context
+import React from "react";
+import PropTypes from "prop-types";
+import warning from "tiny-warning";
+
+const MAX_SIGNED_31_BIT_INT = 1073741823;
+
+const commonjsGlobal =
+  typeof globalThis !== "undefined" // 'global proper'
+    ? // eslint-disable-next-line no-undef
+      globalThis
+    : typeof window !== "undefined"
+    ? window // Browser
+    : typeof global !== "undefined"
+    ? global // node.js
+    : {};
+
+function getUniqueId() {
+  let key = "__global_unique_id__";
+  return (commonjsGlobal[key] = (commonjsGlobal[key] || 0) + 1);
+}
+
+// Inlined Object.is polyfill.
+// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/is
+function objectIs(x, y) {
+  if (x === y) {
+    return x !== 0 || 1 / x === 1 / y;
+  } else {
+    // eslint-disable-next-line no-self-compare
+    return x !== x && y !== y;
+  }
+}
+
+function createEventEmitter(value) {
+  let handlers = [];
+  return {
+    on(handler) {
+      handlers.push(handler);
+    },
+
+    off(handler) {
+      handlers = handlers.filter(h => h !== handler);
+    },
+
+    get() {
+      return value;
+    },
+
+    set(newValue, changedBits) {
+      value = newValue;
+      handlers.forEach(handler => handler(value, changedBits));
+    }
+  };
+}
+
+function onlyChild(children) {
+  return Array.isArray(children) ? children[0] : children;
+}
+
+export default function createReactContext(defaultValue, calculateChangedBits) {
+  const contextProp = "__create-react-context-" + getUniqueId() + "__";
+
+  class Provider extends React.Component {
+    emitter = createEventEmitter(this.props.value);
+
+    static childContextTypes = {
+      [contextProp]: PropTypes.object.isRequired
+    };
+
+    getChildContext() {
+      return {
+        [contextProp]: this.emitter
+      };
+    }
+
+    componentWillReceiveProps(nextProps) {
+      if (this.props.value !== nextProps.value) {
+        let oldValue = this.props.value;
+        let newValue = nextProps.value;
+        let changedBits;
+
+        if (objectIs(oldValue, newValue)) {
+          changedBits = 0; // No change
+        } else {
+          changedBits =
+            typeof calculateChangedBits === "function"
+              ? calculateChangedBits(oldValue, newValue)
+              : MAX_SIGNED_31_BIT_INT;
+          if (process.env.NODE_ENV !== "production") {
+            warning(
+              (changedBits & MAX_SIGNED_31_BIT_INT) === changedBits,
+              "calculateChangedBits: Expected the return value to be a " +
+                "31-bit integer. Instead received: " +
+                changedBits
+            );
+          }
+
+          changedBits |= 0;
+
+          if (changedBits !== 0) {
+            this.emitter.set(nextProps.value, changedBits);
+          }
+        }
+      }
+    }
+
+    render() {
+      return this.props.children;
+    }
+  }
+
+  class Consumer extends React.Component {
+    static contextTypes = {
+      [contextProp]: PropTypes.object
+    };
+
+    observedBits;
+
+    state = {
+      value: this.getValue()
+    };
+
+    componentWillReceiveProps(nextProps) {
+      let { observedBits } = nextProps;
+      this.observedBits =
+        observedBits === undefined || observedBits === null
+          ? MAX_SIGNED_31_BIT_INT // Subscribe to all changes by default
+          : observedBits;
+    }
+
+    componentDidMount() {
+      if (this.context[contextProp]) {
+        this.context[contextProp].on(this.onUpdate);
+      }
+      let { observedBits } = this.props;
+      this.observedBits =
+        observedBits === undefined || observedBits === null
+          ? MAX_SIGNED_31_BIT_INT // Subscribe to all changes by default
+          : observedBits;
+    }
+
+    componentWillUnmount() {
+      if (this.context[contextProp]) {
+        this.context[contextProp].off(this.onUpdate);
+      }
+    }
+
+    getValue() {
+      if (this.context[contextProp]) {
+        return this.context[contextProp].get();
+      } else {
+        return defaultValue;
+      }
+    }
+
+    onUpdate = (newValue, changedBits) => {
+      const observedBits = this.observedBits | 0;
+      if ((observedBits & changedBits) !== 0) {
+        this.setState({ value: this.getValue() });
+      }
+    };
+
+    render() {
+      return onlyChild(this.props.children)(this.state.value);
+    }
+  }
+
+  return {
+    Provider,
+    Consumer
+  };
+}