// App state as Svelte 5 runes. Mirrors backend Status/events and wraps every
// command so failures surface as a notice plus an activity entry.
import { backend } from "./backend";
import { errorText, hostOf } from "./format";
import { SIGN_IN_CANCELLED } from "./types";
import type {
  ConflictChoice,
  InstallProgress,
  LogEvent,
  LogLevel,
  Market,
  Phase,
  Settings,
  StackComponent,
  StackEvent,
  Status,
  SyncConflict,
  Unlisten,
} from "./types";

export type ActionKind =
  | "loading"
  | "sign_in"
  | "signing_in"
  | "install"
  | "offline_unavailable"
  | "signed_out_offline"
  | "installing"
  | "restoring"
  | "syncing"
  | "update"
  | "launch"
  | "stack"
  | "error";

export const STACK_ORDER: readonly StackComponent[] = ["postgres", "api", "tiles", "odian"];

export type StackMap = Record<StackComponent, StackEvent | null>;

/** Which primary action the hub shows for a given status. */
export function deriveAction(s: Status | null): ActionKind {
  if (!s) return "loading";
  switch (s.phase) {
    case "error":
      return "error";
    case "signing_in":
      return "signing_in";
    case "installing":
      return "installing";
    case "restoring":
      return "restoring";
    case "syncing":
      return "syncing";
    case "launching":
    case "running":
      return "stack";
  }
  // idle or checking
  if (s.installed === null) {
    if (!s.online) return "offline_unavailable";
    return s.signed_in ? "install" : "sign_in";
  }
  if (s.update_required) return s.signed_in ? "update" : "sign_in";
  // Launching runs ODIAN as the remembered operator; after Sign out there is none.
  if (s.operator === null) return s.online ? "sign_in" : "signed_out_offline";
  return "launch";
}

type LastOp = { kind: "install" } | { kind: "drive"; path: string } | { kind: "launch" };

interface NotesState {
  key: string | null;
  loading: boolean;
  markdown: string | null;
  error: string | null;
  version: string | null;
  fromCache: boolean;
}

const LOCKED_PHASES: ReadonlySet<Phase> = new Set([
  "signing_in",
  "installing",
  "restoring",
  "syncing",
  "launching",
  "running",
]);
const MAX_LOGS = 250;
const FOCUS_REFRESH_MS = 30_000;
const emptyStack = (): StackMap => ({ postgres: null, api: null, tiles: null, odian: null });
const nowSeconds = () => Math.floor(Date.now() / 1000);

class Launcher {
  readonly kind = backend.kind;
  readonly mock = backend.mock;
  readonly win = backend.window;

  status = $state<Status | null>(null);
  settings = $state<Settings | null>(null);
  progress = $state<InstallProgress | null>(null);
  /** Smoothed bytes/sec for a steadier ETA. */
  speed = $state(0);
  stack = $state<StackMap>(emptyStack());
  logs = $state<LogEvent[]>([]);
  unseen = $state(0);
  unseenError = $state(false);
  activityOpen = $state(false);
  /** Last command failure, shown next to the primary action. */
  notice = $state<string | null>(null);
  /** Name of the command in flight, if any. */
  busy = $state<string | null>(null);
  refreshing = $state(false);
  stopping = $state(false);
  /** The sync review panel. */
  syncOpen = $state(false);
  /** The marketplace panel, and the drive it describes (null: this PC and its DHP). */
  marketOpen = $state(false);
  marketDrive = $state<string | null>(null);
  /** Decisions waiting in this PC's database; null until the panel loads them. */
  conflicts = $state<SyncConflict[] | null>(null);
  notes = $state<NotesState>({
    key: null,
    loading: false,
    markdown: null,
    error: null,
    version: null,
    fromCache: false,
  });

  action: ActionKind = $derived(deriveAction(this.status));
  /** Settings can't change while something is installing or running. */
  locked = $derived(this.status ? LOCKED_PHASES.has(this.status.phase) : false);
  siteName = $derived(this.status ? (this.status.site.name ?? hostOf(this.status.site.url)) : "");
  /** Conflicts plus refused edits from the last sync: what needs the operator. */
  syncAttention = $derived(this.status?.sync ? this.status.sync.conflicts + this.status.sync.rejected : 0);
  notesVersion = $derived(
    this.status ? (this.status.online ? (this.status.available ?? this.status.installed) : this.status.installed) : null,
  );
  notesKey = $derived(this.status ? `${this.status.online}|${this.notesVersion ?? ""}` : null);
  eta = $derived.by(() => {
    const p = this.progress;
    if (!p || p.total_bytes <= 0 || this.speed <= 0) return null;
    return Math.max(0, p.total_bytes - p.done_bytes) / this.speed;
  });

  private lastOp: LastOp | null = null;
  private lastProbe = 0;

  /** Subscribes to backend events and loads the first status. Returns a disposer. */
  start(): () => void {
    let disposed = false;
    const unlisteners: Unlisten[] = [];
    const keep = (p: Promise<Unlisten>) =>
      p.then((unlisten) => {
        if (disposed) unlisten();
        else unlisteners.push(unlisten);
      });

    void (async () => {
      try {
        await Promise.all([
          keep(backend.onStatus((s) => this.applyStatus(s))),
          keep(backend.onInstallProgress((p) => this.applyProgress(p))),
          keep(backend.onStack((e) => (this.stack[e.component] = e))),
          keep(backend.onLog((l) => this.pushLog(l))),
        ]);
        const [status, settings] = await Promise.all([backend.getStatus(), backend.getSettings()]);
        if (disposed) return;
        this.applyStatus(status);
        this.settings = settings;
        // A UI (re)loaded mid-launch redraws the stack from the backend's last known states.
        for (const event of await backend.getStack()) this.stack[event.component] = event;
      } catch (e) {
        this.fail(e);
      }
      if (!disposed) void this.refresh();
    })();

    const onFocus = () => {
      if (this.status?.phase === "idle" && Date.now() - this.lastProbe > FOCUS_REFRESH_MS) void this.refresh();
    };
    window.addEventListener("focus", onFocus);

    return () => {
      disposed = true;
      unlisteners.forEach((u) => u());
      window.removeEventListener("focus", onFocus);
    };
  }

  // ── event reducers ──────────────────────────────────────────────────────

  private applyStatus(next: Status) {
    const prev = this.status;
    if (next.phase === "launching" && prev?.phase !== "launching") this.stack = emptyStack();
    if (next.phase !== "installing" && next.phase !== "restoring") {
      this.progress = null;
      this.speed = 0;
    }
    if (next.phase !== "running" && next.phase !== "launching") this.stopping = false;
    if (prev && prev.phase !== next.phase && LOCKED_PHASES.has(next.phase)) this.notice = null;
    this.status = next;
  }

  private applyProgress(p: InstallProgress) {
    const prev = this.progress;
    const sameStage = prev !== null && prev.stage_index === p.stage_index && prev.stage === p.stage;
    if (p.bytes_per_sec <= 0) this.speed = 0;
    else if (!sameStage || this.speed <= 0) this.speed = p.bytes_per_sec;
    else this.speed = this.speed * 0.85 + p.bytes_per_sec * 0.15;
    this.progress = p;
  }

  private pushLog(entry: LogEvent) {
    this.logs = [entry, ...this.logs].slice(0, MAX_LOGS);
    if (!this.activityOpen) {
      this.unseen++;
      if (entry.level === "error") this.unseenError = true;
    }
  }

  private note(level: LogLevel, message: string) {
    this.pushLog({ level, message, at: nowSeconds() });
  }

  private fail(error: unknown) {
    const message = errorText(error);
    this.notice = message;
    this.note("error", message);
  }

  private async run(name: string, task: () => Promise<void>): Promise<boolean> {
    if (this.busy) return false;
    this.busy = name;
    this.notice = null;
    try {
      await task();
      return true;
    } catch (e) {
      this.fail(e);
      return false;
    } finally {
      this.busy = null;
    }
  }

  // ── commands ────────────────────────────────────────────────────────────

  async refresh() {
    if (this.refreshing) return;
    this.refreshing = true;
    this.lastProbe = Date.now();
    try {
      this.applyStatus(await backend.refresh());
    } catch (e) {
      this.fail(e);
    } finally {
      this.refreshing = false;
    }
  }

  signIn() {
    return this.run("sign_in", async () => {
      try {
        await backend.signIn();
      } catch (e) {
        // Cancelling is the operator's choice, not a failure to show.
        if (errorText(e) !== SIGN_IN_CANCELLED) throw e;
        this.note("info", SIGN_IN_CANCELLED);
      }
      this.applyStatus(await backend.getStatus());
    });
  }

  /** Not wrapped in `run`: the sign-in it cancels is the command in flight. */
  async cancelSignIn() {
    try {
      await backend.cancelSignIn();
    } catch (e) {
      this.fail(e);
    }
  }

  signOut() {
    return this.run("sign_out", async () => this.applyStatus(await backend.signOut()));
  }

  async openExternal(url: string) {
    try {
      await backend.openExternal(url);
    } catch (e) {
      this.fail(e);
    }
  }

  /** The marketplace listing, of this PC's DHP or of a drive. Throws, so the drawer says why. */
  loadMarket(drive?: string): Promise<Market> {
    return backend.getMarket(drive);
  }

  openMarket() {
    this.marketDrive = null;
    this.marketOpen = true;
  }

  /** Installing from a drive starts by looking at what the drive carries. */
  async chooseDrive() {
    const path = await this.pickFolder();
    if (!path) return;
    this.marketDrive = path;
    this.marketOpen = true;
  }

  /** Choose what an install about to run will bring; nothing installed is touched. */
  setMarket(selected: string[], drive?: string) {
    return this.run("market", () => backend.setMarket(selected, drive));
  }

  /** Save the choice of optional items and apply it (downloads show as an install). */
  applyMarket(selected: string[]) {
    return this.run("market", async () => {
      this.lastOp = null;
      await backend.applyMarket(selected);
      this.applyStatus(await backend.getStatus());
    });
  }

  install() {
    return this.run("install", async () => {
      this.lastOp = { kind: "install" };
      await backend.startInstall();
    });
  }

  /**
   * Installing from a drive is a copy the operator chooses first: the marketplace opens on what
   * the drive carries, and starts this once they have picked.
   */
  async installFromDrive(path: string) {
    return this.run("install", async () => {
      this.lastOp = { kind: "drive", path };
      await backend.startInstallFromDrive(path);
    });
  }

  cancelInstall() {
    return this.run("cancel", () => backend.cancelInstall());
  }

  launch() {
    return this.run("launch", async () => {
      this.lastOp = { kind: "launch" };
      await backend.launch();
    });
  }

  stop() {
    return this.run("stop", async () => {
      this.stopping = true;
      try {
        await backend.stop();
      } catch (e) {
        this.stopping = false;
        throw e;
      }
    });
  }

  /** Repeats the failed operation; without history, infers it from status. */
  retry() {
    const op = this.lastOp;
    const s = this.status;
    if (op?.kind === "drive") {
      return this.run("install", () => backend.startInstallFromDrive(op.path));
    }
    if (op?.kind === "install") return this.install();
    if (op?.kind === "launch") return this.launch();
    if (!s) return this.refresh();
    if (s.installed === null || s.update_required) {
      return s.online && s.signed_in ? this.install() : this.refresh();
    }
    return this.launch();
  }

  saveSettings(next: Settings) {
    return this.run("settings", async () => {
      this.applyStatus(await backend.setSettings(next));
      this.settings = await backend.getSettings();
    });
  }

  syncNow() {
    return this.run("sync", async () => {
      await backend.syncNow();
      // The panel lists what the sync just found (or settled).
      if (this.syncOpen) this.conflicts = await backend.getSyncConflicts();
    });
  }

  /** Opens the review panel and loads what waits for a decision. */
  async openSync() {
    this.syncOpen = true;
    await this.run("conflicts", async () => {
      this.conflicts = await backend.getSyncConflicts();
    });
  }

  closeSync() {
    this.syncOpen = false;
  }

  resolveConflict(conflict: SyncConflict, choice: ConflictChoice, value?: unknown) {
    return this.run("resolve", async () => {
      this.conflicts = await backend.resolveSyncConflict(conflict.tbl, conflict.key, choice, value);
    });
  }

  async pickFolder(): Promise<string | null> {
    try {
      return await backend.pickFolder();
    } catch (e) {
      this.fail(e);
      return null;
    }
  }

  async loadNotes() {
    const key = this.notesKey;
    const s = this.status;
    if (key === null || !s) return;
    if (key === this.notes.key && (this.notes.loading || this.notes.markdown !== null)) return;
    const version = this.notesVersion ?? undefined;
    this.notes = {
      key,
      loading: true,
      markdown: null,
      error: null,
      version: version ?? null,
      fromCache: !s.online,
    };
    try {
      const markdown = await backend.getNotes(version);
      if (this.notes.key === key) this.notes = { ...this.notes, loading: false, markdown };
    } catch (e) {
      if (this.notes.key === key) this.notes = { ...this.notes, loading: false, error: errorText(e) };
    }
  }

  // ── activity panel ──────────────────────────────────────────────────────

  setActivityOpen(open: boolean) {
    this.activityOpen = open;
    if (open) {
      this.unseen = 0;
      this.unseenError = false;
    }
  }

  clearLogs() {
    this.logs = [];
    this.unseen = 0;
    this.unseenError = false;
  }

  dismissNotice() {
    this.notice = null;
  }
}

export const launcher = new Launcher();