// Typescript doesn't know about MAX_SAFE_INTEGER??  This was supposed to be
// fixed in typescript 2.0.1 in 2016, but is not working for me in typescript
// 4.2.4 in 2022.  :( https://github.com/microsoft/TypeScript/issues/9937
//const MAX_SAFE_INTEGER = Number.MAX_SAFE_INTEGER;
const MAX_SAFE_INTEGER = 9007199254740991;

// A sane split that splits N *times*, leaving the last chunk unsplit.
function splitN(str: string, delimiter: string, limit: number = MAX_SAFE_INTEGER): string[] {
  if (limit < 1) {
    return [str];
  }
  const at = str.indexOf(delimiter);
  return at === -1 ? [str] : [str.substring(0, at)].concat(splitN(str.substring(at + delimiter.length), delimiter, limit - 1));
}

// A clock that never goes backwards; monotonic.
function Clock() {
  var previousNow = Date.now();
  return {
    now: function (): number {
      const now = Date.now();
      if (now > previousNow) {
        previousNow = now;
        return now;
      }
      return ++previousNow;
    },
  };
}
const clock = Clock();

const Model = {
  addTask: function (timestamp: string, description: string): Element {
    const task = document.createElement("div");
    task.appendChild(document.createTextNode(description));
    task.classList.add("task");
    task.setAttribute("tabindex", "0");
    task.setAttribute("data-created", timestamp);
    task.setAttribute("data-state", "todo");
    document.getElementById("tasks")!.appendChild(task);
    return task;
  },

  edit: function (createTimestamp: string, newDescription: string): Element | null {
    const target = this.getTask(createTimestamp);
    if (!target) return null;
    if (target.hasAttribute("data-description")) {
      // Oh no: An edit has arrived from a replica while a local edit is in progress.
      const input = target.children[0] as HTMLInputElement;
      if (
        input.value === target.getAttribute("data-description") &&
        input.selectionStart === input.value.length &&
        input.selectionEnd === input.value.length
      ) {
        // No local changes have actually been made yet.  Change the contents of the edit box!
        input.value = newDescription;
      } else {
        // No great options.
        // Prefer not to interrupt the local user's edit.
        // The remote edit is mostly lost; this mostly becomes last-write-wins.
        target.setAttribute("data-description", newDescription);
      }
    } else {
      target.textContent = newDescription;
    }
    return target;
  },

  getPriority: function (task: Element): number {
    if (task.hasAttribute("data-priority")) {
      return parseFloat(task.getAttribute("data-priority")!);
    }
    return parseFloat(task.getAttribute("data-created")!);
  },

  getTask: function (createTimestamp: string) {
    for (const task of document.getElementsByClassName("task")) {
      if (task.getAttribute("data-created") === createTimestamp) {
        return task;
      }
    }
  },

  setPriority: function (createTimestamp: string, priority: number): Element | null {
    const target = this.getTask(createTimestamp);
    if (!target) return null;
    target.setAttribute("data-priority", `${priority}`);
    for (const task of document.getElementsByClassName("task")) {
      if (task !== target && this.getPriority(task) > priority) {
        task.parentElement!.insertBefore(target, task);
        return target;
      }
    }
    document.getElementById("tasks")!.appendChild(target);
    return target;
  },

  setState: function (stateTimestamp: string, createTimestamp: string, state: string) {
    const task = this.getTask(createTimestamp);
    if (task) {
      task.setAttribute("data-state", state);
    }
  },
};

function Log(prefix: string = "vp-") {
  var next_log_index = 0;
  return {
    apply: function (entry: string) {
      const [timestamp, command, data] = splitN(entry, " ", 2);
      if (command == "Create") {
        return Model.addTask(timestamp, data);
      }
      if (command == "Edit") {
        const [createTimestamp, description] = splitN(data, " ", 1);
        return Model.edit(createTimestamp, description);
      }
      if (command == "State") {
        const [createTimestamp, state] = splitN(data, " ", 1);
        return Model.setState(timestamp, createTimestamp, state);
      }
      if (command == "Priority") {
        const [createTimestamp, newPriority] = splitN(data, " ", 1);
        return Model.setPriority(createTimestamp, parseFloat(newPriority));
      }
    },

    record: function (entry: string) {
      window.localStorage.setItem(`${prefix}${next_log_index++}`, entry);
    },

    recordAndApply: function (entry: string) {
      this.record(entry);
      return this.apply(entry);
    },

    replay: function () {
      while (true) {
        const entry = window.localStorage.getItem(`${prefix}${next_log_index}`);
        if (entry === null) {
          break;
        }
        this.apply(entry);
        next_log_index++;
      }
    },
  };
}
const log = Log();

function UI() {
  const undoLog: string[] = [];
  return {
    addTask: function (description: string): Element {
      const now = clock.now();
      undoLog.push(`State ${now} deleted`);
      return <Element>log.recordAndApply(`${now} Create ${description}`);
    },
    edit: function (createTimestamp: string, newDescription: string, oldDescription: string) {
      undoLog.push(`Edit ${createTimestamp} ${oldDescription}`);
      return log.recordAndApply(`${clock.now()} Edit ${createTimestamp} ${newDescription}`);
    },
    setPriority: function (createTimestamp: string, newPriority: number, oldPriority: number) {
      undoLog.push(`Priority ${createTimestamp} ${oldPriority}`);
      return log.recordAndApply(`${clock.now()} Priority ${createTimestamp} ${newPriority}`);
    },
    setState: function (createTimestamp: string, newState: string, oldState: string) {
      undoLog.push(`State ${createTimestamp} ${oldState}`);
      return log.recordAndApply(`${clock.now()} State ${createTimestamp} ${newState}`);
    },
    undo: function () {
      if (undoLog.length > 0) {
        return log.recordAndApply(`${clock.now()} ${undoLog.pop()}`);
      }
    },
  };
}
const ui = UI();

enum CommitOrAbort {
  Commit,
  Abort,
}

function BrowserUI() {
  var currentViewState = "todo";
  var taskFocusedBeforeJumpingToInput: HTMLElement | null = null;
  return {
    addTask: function (event: KeyboardEvent) {
      const input = <HTMLInputElement>document.getElementById("taskName");
      if (input.value) {
        const task = ui.addTask(input.value);
        if (currentViewState === "todo") {
          task instanceof HTMLElement && task.focus();
        } else if (this.returnFocusAfterInput()) {
        } else {
          this.firstVisibleTask()?.focus();
        }
        input.value = "";
        if (event.getModifierState("Control")) {
          this.setPriority(task, null, document.getElementsByClassName("task")[0]);
        }
      }
    },

    beginEdit: function (event: Event) {
      const task = document.activeElement;
      if (!task) return;
      const input = document.createElement("input");
      const oldDescription = task.textContent!;
      task.setAttribute("data-description", oldDescription);
      input.value = oldDescription;
      input.addEventListener("blur", this.completeEdit, { once: true });
      task.textContent = "";
      task.appendChild(input);
      input.focus();
      event.preventDefault();
    },

    completeEdit: function (event: Event, resolution: CommitOrAbort = CommitOrAbort.Commit) {
      const input = event.target as HTMLInputElement;
      const task = input.parentElement!;
      const oldDescription = task.getAttribute("data-description")!;
      const newDescription = input.value;
      input.removeEventListener("blur", this.completeEdit);
      task.removeChild(task.children[0]);
      task.removeAttribute("data-description");
      task.focus();
      if (newDescription === oldDescription || resolution === CommitOrAbort.Abort) {
        task.textContent = oldDescription;
      } else {
        ui.edit(task.getAttribute("data-created")!, newDescription, oldDescription);
      }
    },

    firstVisibleTask: function () {
      for (const task of document.getElementsByClassName("task")) {
        if (task instanceof HTMLElement && task.getAttribute("data-state") === currentViewState) {
          return task;
        }
      }
    },

    focusTaskNameInput: function (event: Event) {
      if (document.activeElement instanceof HTMLElement) {
        taskFocusedBeforeJumpingToInput = document.activeElement;
      }
      document.getElementById("taskName")!.focus();
      event.preventDefault();
    },

    visibleTaskAtOffset(task: Element, offset: number): Element {
      var cursor: Element | null = task;
      var valid_cursor = cursor;
      const increment = offset / Math.abs(offset);
      while (true) {
        cursor = increment > 0 ? cursor.nextElementSibling : cursor.previousElementSibling;
        if (!cursor || !(cursor instanceof HTMLElement)) break;
        if (cursor.getAttribute("data-state")! === currentViewState) {
          offset -= increment;
          valid_cursor = cursor;
        }
        if (Math.abs(offset) < 0.5) break;
      }
      return valid_cursor;
    },

    moveCursor: function (offset: number): boolean {
      const active = document.activeElement;
      if (!active) return false;
      const dest = this.visibleTaskAtOffset(active, offset);
      if (dest !== active && dest instanceof HTMLElement) {
        dest.focus();
        return true;
      }
      return false;
    },

    moveTask: function (offset: number) {
      const active = document.activeElement;
      if (!active) return;
      const dest = this.visibleTaskAtOffset(active, offset);
      if (dest === active) return; // Already extremal
      var onePastDest: Element | null = this.visibleTaskAtOffset(dest, offset / Math.abs(offset));
      if (onePastDest == dest) onePastDest = null; // Will become extremal
      if (offset > 0) {
        this.setPriority(active, dest, onePastDest);
      } else {
        this.setPriority(active, onePastDest, dest);
      }
    },

    returnFocusAfterInput: function (): boolean {
      if (taskFocusedBeforeJumpingToInput) {
        taskFocusedBeforeJumpingToInput.focus();
        return true;
      }
      return false;
    },

    // Change task's priority to be between other tasks a and b.
    setPriority: function (task: Element, a: Element | null, b: Element | null) {
      const aPriority = a === null ? 0 : Model.getPriority(a);
      const bPriority = b === null ? clock.now() : Model.getPriority(b);
      console.assert(aPriority < bPriority, aPriority, "<", bPriority);
      const span = bPriority - aPriority;
      const newPriority = aPriority + 0.1 * span + 0.8 * span * Math.random();
      console.assert(aPriority < newPriority && newPriority < bPriority, aPriority, "<", newPriority, "<", bPriority);
      const newPriorityRounded = Math.round(newPriority);
      const okToRound = aPriority < newPriorityRounded && newPriorityRounded < bPriority;
      ui.setPriority(task.getAttribute("data-created")!, okToRound ? newPriorityRounded : newPriority, Model.getPriority(task));
      task instanceof HTMLElement && task.focus();
    },

    setState: function (newState: string) {
      const task = document.activeElement;
      if (!task) return;
      const oldState = task.getAttribute("data-state")!;
      if (newState === oldState) return;
      const createTimestamp = task.getAttribute("data-created")!;
      this.moveCursor(1) || this.moveCursor(-1);
      return ui.setState(createTimestamp, newState, oldState);
    },

    setView: function (state: string) {
      const sheet = (document.getElementById("viewStyle") as HTMLStyleElement).sheet!;
      sheet.insertRule(`.task:not([data-state=${state}]) { display: none }`);
      sheet.removeRule(1);
      currentViewState = state;
      if (document.activeElement?.getAttribute("data-state") !== state) {
        this.firstVisibleTask()?.focus();
      }
    },

    undo: function () {
      const ret = ui.undo();
      if (ret && ret instanceof HTMLElement) ret.focus();
    },
  };
}
const browserUI = BrowserUI();

enum InputState {
  Command,
  View,
}
var inputState = InputState.Command;

function handleKey(event: any) {
  if (event.target.tagName === "INPUT") {
    if (event.target.id === "taskName") {
      if (event.key == "Enter") return browserUI.addTask(event);
      if (event.key == "Escape") return browserUI.returnFocusAfterInput();
    } else {
      if (event.key == "Enter") return browserUI.completeEdit(event);
      if (event.key == "Escape") return browserUI.completeEdit(event, CommitOrAbort.Abort);
    }
  } else {
    if (inputState === InputState.Command) {
      if (event.key == "j") return browserUI.moveCursor(1);
      if (event.key == "k") return browserUI.moveCursor(-1);
      if (event.key == "J") return browserUI.moveTask(1);
      if (event.key == "K") return browserUI.moveTask(-1);
      if (event.key == "n") return browserUI.focusTaskNameInput(event);
      if (event.key == "c") return browserUI.setState("cancelled");
      if (event.key == "d") return browserUI.setState("done");
      if (event.key == "q") return browserUI.setState("todo");
      if (event.key == "s") return browserUI.setState("someday-maybe");
      if (event.key == "w") return browserUI.setState("waiting");
      if (event.key == "X") return browserUI.setState("deleted");
      if (event.key == "u") return browserUI.undo();
      if (event.key == "e") return browserUI.beginEdit(event);
      if (event.key == "v") return (inputState = InputState.View);
    } else if (inputState === InputState.View) {
      inputState = InputState.Command;
      if (event.key == "c") return browserUI.setView("cancelled");
      if (event.key == "d") return browserUI.setView("done");
      if (event.key == "q") return browserUI.setView("todo");
      if (event.key == "s") return browserUI.setView("someday-maybe");
      if (event.key == "w") return browserUI.setView("waiting");
      if (event.key == "x") return browserUI.setView("deleted");
    }
  }
}

function browserInit() {
  document.body.addEventListener("keydown", handleKey, { capture: false });
  log.replay();
  browserUI.firstVisibleTask()?.focus();
}