// 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));
}

const Model = {
  addTask: function (timestamp: string, description: string): Element {
    const task = document.createElement("div");
    task.appendChild(document.createTextNode(description));
    task.setAttribute("class", "task");
    task.setAttribute("tabindex", "0");
    task.setAttribute("data-created", timestamp);
    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 === 0 &&
        input.selectionEnd === input.value.length
      ) {
        // No local changes have actually been made yet.  Change the contents of the edit box!
        input.value = newDescription;
        input.select();
      } 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")!);
  },

  getState: function (task: Element): string {
    return task.getAttribute("data-state") ?? "todo";
  },

  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);
      if (task instanceof HTMLElement) {
        task.style.display = state == "todo" ? "block" : "none"; // Until view filtering
      }
    }
  },
};

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();

const undoLog: string[] = [];

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

const BrowserUI = {
  addTask: function (event: KeyboardEvent) {
    const input = <HTMLInputElement>document.getElementById("taskName");
    if (input.value) {
      const task = UI.addTask(input.value);
      if (task && task instanceof HTMLElement) task.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", BrowserUI.completeEdit, { once: true });
    task.textContent = "";
    task.appendChild(input);
    input.focus();
    input.select();
    event.preventDefault();
  },

  completeEdit: function (event: Event) {
    const input = event.target as HTMLInputElement;
    const task = input.parentElement!;
    const oldDescription = task.getAttribute("data-description")!;
    const newDescription = input.value;
    input.removeEventListener("blur", BrowserUI.completeEdit);
    task.removeChild(task.children[0]);
    task.removeAttribute("data-description");
    task.focus();
    if (newDescription === oldDescription) {
      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.style.display !== "none") {
        return task;
      }
    }
  },

  focusTaskNameInput: function (event: Event) {
    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.style.display !== "none") {
        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);
    }
  },

  // 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 ? Date.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 = Model.getState(task);
    if (newState === oldState) return;
    const createTimestamp = task.getAttribute("data-created")!;
    this.moveCursor(1) || this.moveCursor(-1);
    return UI.setState(createTimestamp, newState, oldState);
  },

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

function handleKey(event: any) {
  if (event.target.tagName === "INPUT") {
    if (event.target.id === "taskName") {
      if (event.key == "Enter") return BrowserUI.addTask(event);
    } else {
      if (event.key == "Enter") return BrowserUI.completeEdit(event);
    }
  } else {
    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 == "s") return BrowserUI.setState("someday-maybe");
    if (event.key == "w") return BrowserUI.setState("waiting");
    if (event.key == "d") return BrowserUI.setState("done");
    if (event.key == "c") return BrowserUI.setState("cancelled");
    if (event.key == "t") return BrowserUI.setState("todo");
    if (event.key == "X") return BrowserUI.setState("deleted");
    if (event.key == "u") return BrowserUI.undo();
    if (event.key == "e") return BrowserUI.beginEdit(event);
  }
}

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