import type { ViewStateResult, WorkspaceLeaf } from "obsidian";
import { ItemView, TFile } from "obsidian";
import { mount, unmount } from "svelte";
import type { Rect } from "./inset";
import { insetFor } from "./inset";
import type BeaverPlugin from "./main";
import { PanelState } from "./state.svelte";
import App from "./ui/app.svelte";

export const VIEW_TYPE_PANEL = "beaver-panel";

// Bars that paint over a leaf instead of shortening it. On a phone the navbar
// sits under every view, including the one filling the screen.
const BOTTOM_BARS = [".status-bar", ".mobile-navbar", ".mobile-toolbar"];

// The keyboard and the navbar both animate, and Obsidian hides the navbar
// *after* the keyboard is up: the inset is re-measured every frame until the
// reading has held still long enough to outlast both moves.
const STEADY_FRAMES = 12;

/** Obsidian's Capacitor keyboard events on mobile; absent on the desktop. */
const KEYBOARD_EVENTS = [
  "keyboardWillShow",
  "keyboardDidShow",
  "keyboardWillHide",
  "keyboardDidHide",
] as const;

interface SavedState {
  follow?: unknown;
  selected?: unknown;
}

// One panel leaf: a sidedock column, a tab, or the phone screen. Follows
// the active note's ``conversation_id`` unless pinned, and remembers both
// across restarts through the workspace layout.
export class PanelView extends ItemView {
  readonly state = new PanelState();
  private readonly plugin: BeaverPlugin;
  private root: Record<string, unknown> | null = null;
  private settling: number | null = null;

  constructor(leaf: WorkspaceLeaf, plugin: BeaverPlugin) {
    super(leaf);
    this.plugin = plugin;
    this.navigation = false;
  }

  getViewType(): string {
    return VIEW_TYPE_PANEL;
  }

  getDisplayText(): string {
    return "Beaver";
  }

  getIcon(): string {
    return "bot";
  }

  getState(): Record<string, unknown> {
    return { follow: this.state.follow, selected: this.state.selected };
  }

  async setState(state: unknown, result: ViewStateResult): Promise<void> {
    const saved = (state ?? {}) as SavedState;
    if (typeof saved.follow === "boolean") {
      this.state.follow = saved.follow;
    }
    if (typeof saved.selected === "string" || saved.selected === null) {
      this.state.selected = saved.selected;
    }
    await super.setState(state, result);
  }

  onOpen(): Promise<void> {
    this.contentEl.empty();
    this.contentEl.style.padding = "0";
    this.contentEl.style.overflow = "hidden";
    this.registerEvent(
      this.app.workspace.on("file-open", (file) => {
        // ``null`` means the active leaf is not a file (this panel got
        // focus, say): keep following the last note rather than drop it.
        if (file) {
          this.follow(file);
        }
      })
    );
    this.registerEvent(
      this.app.metadataCache.on("changed", (file) => {
        // The note we follow just got its conversation_id - typically
        // right after the first send. Re-resolve.
        if (file.path === this.state.sourcePath) {
          this.follow(file);
        }
      })
    );
    this.registerEvent(this.app.workspace.on("resize", () => this.settle()));
    this.registerEvent(
      this.app.workspace.on("layout-change", () => this.settle())
    );
    // The keyboard resizes the visual viewport only: no workspace event
    // fires, so the composer would stay behind it without these two.
    const vv = window.visualViewport;
    if (vv) {
      const onViewport = () => this.settle();
      vv.addEventListener("resize", onViewport);
      vv.addEventListener("scroll", onViewport);
      this.register(() => {
        vv.removeEventListener("resize", onViewport);
        vv.removeEventListener("scroll", onViewport);
      });
    }
    // Focus opens the keyboard, blur closes it; both animate, and on the way
    // out the navbar comes back, so the leaf has to be re-measured after.
    this.registerDomEvent(this.contentEl, "focusin", () => this.settle());
    this.registerDomEvent(this.contentEl, "focusout", () => this.settle());
    // Obsidian's own keyboard events (Capacitor, mobile only) fire before the
    // animation and again as the navbar returns, which visualViewport alone
    // does not always report.
    for (const name of KEYBOARD_EVENTS) {
      const onKeyboard = () => this.settle();
      window.addEventListener(name, onKeyboard);
      this.register(() => window.removeEventListener(name, onKeyboard));
    }
    this.follow(this.app.workspace.getActiveFile());
    this.plugin.views.add(this);
    this.mountApp();
    this.settle();
    return Promise.resolve();
  }

  /**
   * Re-measure until the viewport stops moving. The keyboard animates both
   * ways and Obsidian hides its navbar while it is up, so a fixed delay lands
   * mid-animation; a frame loop that stops once two readings agree does not
   * care how long the animation takes, or whether any event fires at all -
   * which is the case in a sidedock drawer.
   */
  private settle(): void {
    let last = Number.NaN;
    let steady = 0;
    // A fresh trigger restarts the watch rather than being dropped: the navbar
    // coming back is a second move, after the first one has settled.
    if (this.settling !== null) {
      cancelAnimationFrame(this.settling);
    }
    const tick = () => {
      const floor = this.inset();
      steady = floor === last ? steady + 1 : 0;
      last = floor;
      if (steady >= STEADY_FRAMES) {
        this.settling = null;
        return;
      }
      this.settling = requestAnimationFrame(tick);
    };
    this.settling = requestAnimationFrame(tick);
    this.register(() => {
      if (this.settling !== null) {
        cancelAnimationFrame(this.settling);
        this.settling = null;
      }
    });
  }

  // Whatever floats over the bottom of this leaf, measured rather than
  // guessed. Returns the inset it wrote, so the settle loop can tell when the
  // reading stops changing; the arithmetic itself lives in ``inset.ts``.
  private inset(): number {
    const box = this.contentEl.getBoundingClientRect();
    if (box.height <= 0) {
      return Number.NaN;
    }
    const bars: Rect[] = [];
    for (const selector of BOTTOM_BARS) {
      const node = document.querySelector<HTMLElement>(selector);
      if (node && node.offsetParent !== null) {
        bars.push(node.getBoundingClientRect());
      }
    }
    const vv = window.visualViewport;
    const inset = insetFor(
      box,
      bars,
      vv ? { height: vv.height, offsetTop: vv.offsetTop } : null
    );
    this.contentEl.style.setProperty("--beaver-inset-bottom", `${inset}px`);
    return inset;
  }

  async onClose(): Promise<void> {
    this.plugin.views.delete(this);
    await this.unmountApp();
    this.contentEl.empty();
  }

  // The active note changed: remember it, and switch to its conversation
  // when following and it has one.
  follow(file: TFile | null): void {
    if (!(file instanceof TFile)) {
      return;
    }
    this.state.sourcePath = file.path;
    if (!this.state.follow) {
      return;
    }
    const id = this.plugin.conversationIdOf(file);
    if (id) {
      this.state.selected = id;
      this.state.companion = !this.inTabs();
    }
  }

  show(id: string): void {
    this.state.selected = id;
    this.state.companion = false;
  }

  private inTabs(): boolean {
    return this.leaf.getRoot() === this.app.workspace.rootSplit;
  }

  // Settings changed: the client is built from them, so rebuild the tree.
  async remount(): Promise<void> {
    await this.unmountApp();
    this.mountApp();
  }

  private mountApp(): void {
    this.root = mount(App, {
      props: {
        app: this.app,
        chatsFolder: () => this.plugin.settings.chatsFolder,
        client: this.plugin.apiClient(),
        component: this,
        onOpenSettings: () => this.plugin.openSettings(),
        state: this.state,
      },
      target: this.contentEl,
    });
  }

  private async unmountApp(): Promise<void> {
    if (this.root) {
      await unmount(this.root);
      this.root = null;
    }
  }
}