// 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) {
    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);
    task.focus();
  },

  destroyTask: function (createTimestamp: string) {
    const task = this.getTask(createTimestamp);
    if (task) {
      task.parentElement!.removeChild(task);
    }
  },

  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) {
    const target = this.getTask(createTimestamp);
    if (!target) return;
    target.setAttribute("data-priority", `${priority}`);
    for (const task of document.getElementsByClassName("task")) {
      if (task !== target && this.getPriority(task) > priority) {
        task.parentElement!.insertBefore(target, task);
        target instanceof HTMLElement && target.focus();
        return;
      }
    }
    document.getElementById("tasks")!.appendChild(target);
    target instanceof HTMLElement && target.focus();
  },

  setState: function (stateTimestamp: string, createTimestamp: string, state: string) {
    const task = this.getTask(createTimestamp);
    if (task) {
      task.setAttribute(`data-${state}`, stateTimestamp);
      if (task instanceof HTMLElement) {
        task.style.display = "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") {
        Model.addTask(timestamp, data);
      }
      if (command == "Destroy") {
        Model.destroyTask(data.split(" ", 1)[0]);
      }
      if (command == "State") {
        const [createTimestamp, state] = splitN(data, " ", 1);
        Model.setState(timestamp, createTimestamp, state);
      }
      if (command == "Priority") {
        const [createTimestamp, newPriority] = splitN(data, " ", 1);
        Model.setPriority(createTimestamp, parseFloat(newPriority));
      }
    },

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

    recordAndApply: function (entry: string) {
      this.record(entry);
      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 UI = {
  addTask: function (description: string) {
    log.recordAndApply(`${Date.now()} Create ${description}`);
  },
  destroyTask: function (createTimestamp: string) {
    log.recordAndApply(`${Date.now()} Destroy ${createTimestamp} ${Model.getTask(createTimestamp)?.textContent}`);
  },
  setPriority: function (createTimestamp: string, priority: number) {
    log.recordAndApply(`${Date.now()} Priority ${createTimestamp} ${priority}`);
  },
  setState: function (createTimestamp: string, state: string) {
    log.recordAndApply(`${Date.now()} State ${createTimestamp} ${state}`);
  },
};

const BrowserUI = {
  addTask: function () {
    const input = <HTMLInputElement>document.getElementById("taskName");
    if (input.value) {
      UI.addTask(input.value);
      input.value = "";
    }
  },

  destroyTask: function () {
    const createTimestamp = document.activeElement?.getAttribute("data-created");
    this.moveCursor(1) || this.moveCursor(-1);
    return UI.destroyTask(createTimestamp!);
  },

  focusTaskNameInput: function (event: any) {
    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);
  },

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

function handleKey(event: any) {
  if (event.target.tagName === "INPUT") {
    if (event.key == "Enter") return BrowserUI.addTask();
  } 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 == "X") return BrowserUI.destroyTask();
  }
}

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