/*
  Typing affordances in the composer: `@` to attach something by name, and
  (from the commands section below) `/` to run something instead of sending.

  Both are the same shape -- a token at the caret opens a menu, the menu
  filters as you type, and choosing replaces the token -- so they share one
  menu and one keyboard handler rather than fighting over the composer.

  Three things here are not obvious.

  The keydown listener is registered with `capture: true`. app.js already has a
  document-level Enter handler that submits the form, and listeners on the same
  element in the same phase fire in registration order -- app.js loads first,
  so a bubble-phase listener here would never get to say "that Enter chose a
  menu item, it did not send the message".

  Nothing is inserted into the composer as HTML. Every name in the menu came
  off somebody's filesystem or out of their library.

  A chip is a chip. Choosing a file posts to a route that returns the same
  attachment chip an upload returns, so the composer learns nothing new and the
  remove button, the hidden file_ids input and `claim()` on send all work
  already.
*/
(function () {
  "use strict";

  var menu = null;
  var list = null;
  var open = false;
  var kind = "";
  var pending = null;
  var active = -1;

  /* commands.js loads first and defines these. Guarded anyway so that a page
     which does not carry it -- or one where it failed to parse -- still gets
     `@`, and a message beginning with a slash is simply sent. */
  function commands() {
    return window.lembasCommands || {
      list: function () { return document.createElement("div"); },
      find: function () { return null; },
      run: function () {}
    };
  }

  function commandList(query) { return commands().list(query); }
  function commandIn(value) { return commands().find(value); }
  function runCommand(name, rest) { commands().run(name, rest); }

  /* --- Where we are ------------------------------------------------------- */
  function composer() {
    return document.querySelector("[data-composer-input]");
  }

  function context() {
    var box = document.querySelector(".composer");
    var picker = document.querySelector('select[name="ssh_profile_id"]');
    var dir = document.querySelector("[data-dir-value]");
    return {
      chatId: (box && box.dataset.chatId) || "",
      /* A chat under way carries its connection on the composer; a new one is
         still choosing it, so the select and the hidden field are the truth. */
      profileId: picker ? picker.value : (box && box.dataset.profileId) || "",
      projectDir: dir ? dir.value : (box && box.dataset.projectDir) || ""
    };
  }

  /*
    The token being typed, or null.

    `@` is claimed anywhere it follows whitespace, so `see @src/main.py` works
    mid-sentence, but not inside an email address -- `a@b` is not a mention and
    treating it as one would open a menu every time somebody typed one.
  */
  function tokenAt(input) {
    var value = input.value;
    var caret = input.selectionStart;
    if (caret !== input.selectionEnd) return null;

    var before = value.slice(0, caret);
    var at = before.lastIndexOf("@");
    if (at !== -1 && (at === 0 || /\s/.test(before[at - 1]))) {
      var query = before.slice(at + 1);
      if (!/\s/.test(query)) return { kind: "@", query: query, start: at, end: caret };
    }
    /* A slash command is only ever the first thing in the box. Anywhere else a
       slash is a path, a date or a fraction. */
    if (before[0] === "/" && before[1] !== "/") {
      var word = before.slice(1);
      if (!/\s/.test(word) && caret === value.length) {
        return { kind: "/", query: word, start: 0, end: caret };
      }
    }
    return null;
  }

  /* --- The menu ----------------------------------------------------------- */
  function build() {
    if (menu) return;
    var host = document.querySelector(".composer__inner");
    if (!host) return;
    menu = document.createElement("div");
    menu.className = "composer-menu";
    menu.setAttribute("role", "listbox");
    menu.hidden = true;
    list = document.createElement("div");
    menu.appendChild(list);
    host.insertBefore(menu, host.firstChild);

    menu.addEventListener("mousedown", function (event) {
      /* Before the composer loses focus, or the caret position the choice is
         about to be written at is already gone. */
      event.preventDefault();
    });
    menu.addEventListener("click", function (event) {
      var option = event.target.closest("[data-mention-token], [data-command]");
      if (option) choose(option);
    });
  }

  function show() {
    build();
    if (!menu) return;
    menu.hidden = false;
    open = true;
  }

  function hide() {
    if (!menu) return;
    menu.hidden = true;
    open = false;
    kind = "";
    active = -1;
  }

  function options() {
    return menu ? Array.prototype.slice.call(
      menu.querySelectorAll("[data-mention-token], [data-command]")
    ) : [];
  }

  function highlight(index) {
    var all = options();
    if (!all.length) return;
    active = (index + all.length) % all.length;
    all.forEach(function (option, position) {
      option.classList.toggle("is-selected", position === active);
    });
    if (all[active].scrollIntoView) all[active].scrollIntoView({ block: "nearest" });
  }

  /* --- Filling it --------------------------------------------------------- */
  function loadMentions(query) {
    var where = context();
    var url =
      "/api/files/mention-picker?q=" + encodeURIComponent(query) +
      "&chat_id=" + encodeURIComponent(where.chatId) +
      "&profile_id=" + encodeURIComponent(where.profileId) +
      "&project_dir=" + encodeURIComponent(where.projectDir);

    fetch(url, { credentials: "same-origin" })
      .then(function (response) { return response.text(); })
      .then(function (html) {
        if (kind !== "@") return;
        list.innerHTML = html;
        show();
        highlight(0);
      })
      .catch(function () { hide(); });
  }

  function refresh() {
    var input = composer();
    if (!input) return;
    var token = tokenAt(input);
    if (!token) return hide();

    kind = token.kind;
    if (token.kind === "/") {
      list.innerHTML = "";
      list.appendChild(commandList(token.query));
      show();
      highlight(0);
      return;
    }

    clearTimeout(pending);
    pending = setTimeout(function () { loadMentions(token.query); }, 150);
  }

  /* --- Choosing ----------------------------------------------------------- */
  function replaceToken(text) {
    var input = composer();
    var token = tokenAt(input);
    if (!input || !token) return;
    var head = input.value.slice(0, token.start);
    var tail = input.value.slice(token.end);
    var written = (token.kind === "@" ? "@" : "/") + text + " ";
    input.value = head + written + tail;
    var caret = head.length + written.length;
    input.setSelectionRange(caret, caret);
    if (window.lembas && window.lembas.autosize) window.lembas.autosize(input);
    input.focus();
  }

  function choose(option) {
    if (option.dataset.command) {
      hide();
      runCommand(option.dataset.command, "");
      return;
    }

    var where = context();
    /* The reference stays in the sentence being written *and* the contents
       come along as a chip. The first is what makes "change the thing in
       @main.py" read as a sentence; the second is what stops a small model
       having to spend a round fetching it. */
    replaceToken(option.dataset.mentionToken);
    hide();

    var body = new FormData();
    body.append("chat_id", where.chatId);
    if (option.dataset.mentionFile) {
      body.append("profile_id", where.profileId);
      body.append("path", option.dataset.mentionFile);
      attach("/api/files/from-project", body);
    } else if (option.dataset.mentionKnowledge) {
      body.append("document_id", option.dataset.mentionKnowledge);
      attach("/api/files/from-knowledge", body);
    }
  }

  function attach(url, body) {
    var target = document.getElementById("attachments");
    if (!target) return;
    fetch(url, { method: "POST", body: body, credentials: "same-origin" })
      .then(function (response) { return response.text(); })
      .then(function (html) {
        target.insertAdjacentHTML("beforeend", html);
        // The chip's remove button is htmx-driven and inert until announced.
        if (window.htmx) window.htmx.process(target.lastElementChild);
      })
      .catch(function () {
        if (window.lembas) window.lembas.notify("Could not attach that.", { kind: "error" });
      });
  }

  /* --- Keys --------------------------------------------------------------- */
  document.addEventListener(
    "keydown",
    function (event) {
      var input = event.target.closest && event.target.closest("[data-composer-input]");
      if (!input) return;

      if (open) {
        if (event.key === "Escape") {
          event.stopPropagation();
          event.preventDefault();
          return hide();
        }
        if (event.key === "ArrowDown") {
          event.preventDefault();
          return highlight(active + 1);
        }
        if (event.key === "ArrowUp") {
          event.preventDefault();
          return highlight(active - 1);
        }
        if (event.key === "Enter" || event.key === "Tab") {
          var all = options();
          if (all.length && active >= 0) {
            /* Capture phase, so app.js's Enter-to-send never sees this one.
               Without stopping it the message would be sent *and* the menu
               item chosen. */
            event.preventDefault();
            event.stopPropagation();
            choose(all[active]);
            return;
          }
        }
      }

      if (event.key === "Enter" && !event.shiftKey && !event.isComposing) {
        /* Not a menu key: a command typed in full and submitted. Handled here
           rather than on submit so the form is never posted at all -- a
           command is not a message and must not become one if it is unknown. */
        var command = commandIn(input.value);
        if (command) {
          event.preventDefault();
          event.stopPropagation();
          input.value = "";
          if (window.lembas && window.lembas.autosize) window.lembas.autosize(input);
          runCommand(command.name, command.rest);
        }
      }
    },
    true
  );

  document.addEventListener("input", function (event) {
    if (event.target.closest("[data-composer-input]")) refresh();
  });

  document.addEventListener("click", function (event) {
    if (!event.target.closest(".composer-menu") &&
        !event.target.closest("[data-composer-input]")) hide();
  });

  /* Opening the menu from a button, for anyone who would rather press than
     type. Inserts the character and lets the normal path take over. */
  document.addEventListener("click", function (event) {
    var button = event.target.closest("[data-mention-open]");
    if (!button) return;
    event.preventDefault();
    var input = composer();
    if (!input) return;
    input.focus();
    var caret = input.selectionStart;
    var lead = caret && !/\s/.test(input.value[caret - 1]) ? " @" : "@";
    input.setRangeText(lead, caret, caret, "end");
    refresh();
  });

  window.lembas = window.lembas || {};
  window.lembas.closeComposerMenu = hide;
})();