// Per-game runes store that owns the local order draft. Mirrors the
// Phase 11 `GameStateStore` lifecycle: one instance per game, created
// in `routes/games/[id]/+layout.svelte`, exposed to descendants via
// Svelte context, disposed when the layout unmounts.
//
// Draft state is persisted into the platform `Cache` under the
// `order-drafts` namespace with a per-game key, so a reload, a
// browser restart, or a navigation through the lobby and back into
// the same game restores the previously composed list. Phase 14
// will add the submit pipeline that drains the draft to the server;
// Phase 26 will hide the order tab in history mode through a flag
// passed by the layout (the store itself remains alive across that
// transition so the draft survives history-mode round-trips).
//
// The store deliberately carries no Svelte component imports so it
// can be tested directly with a synthetic `Cache` without rendering
// any UI.

import type { Cache } from "../platform/store/index";
import type { GalaxyClient } from "../api/galaxy-client";
import { fetchOrder } from "./order-load";
import type { CommandStatus, OrderCommand } from "./order-types";
import { validateEntityName } from "$lib/util/entity-name";

const NAMESPACE = "order-drafts";
const draftKey = (gameId: string): string => `${gameId}/draft`;

/**
 * ORDER_DRAFT_CONTEXT_KEY is the Svelte context key the in-game shell
 * layout uses to expose its `OrderDraftStore` instance to descendants.
 * The order tab and any later command-builder UI resolve the store via
 * `getContext(ORDER_DRAFT_CONTEXT_KEY)`.
 */
export const ORDER_DRAFT_CONTEXT_KEY = Symbol("order-draft");

type Status = "idle" | "ready" | "error";

export class OrderDraftStore {
	commands: OrderCommand[] = $state([]);
	statuses: Record<string, CommandStatus> = $state({});
	updatedAt = $state(0);
	status: Status = $state("idle");
	error: string | null = $state(null);

	/**
	 * needsServerHydration is `true` when the cache row for this game
	 * was absent at `init` time. The layout reads it after both
	 * `gameState.init` and `orderDraft.init` resolve and, if `true`,
	 * calls `hydrateFromServer` once the current turn is known.
	 * An explicitly empty cache row sets it to `false` (the user has
	 * an empty draft, not a missing one).
	 */
	needsServerHydration = $state(false);

	private cache: Cache | null = null;
	private gameId = "";
	private destroyed = false;

	/**
	 * init loads the persisted draft for `opts.gameId` from `opts.cache`
	 * into `commands` and flips `status` to `ready`. The call is
	 * idempotent on the same store instance — the layout always
	 * constructs a fresh store per game, so there is no need to support
	 * mid-life game switching here.
	 *
	 * When the cache row is absent, `needsServerHydration` is set to
	 * `true`; the layout fans out a `hydrateFromServer` call once the
	 * current turn is known. An explicitly empty cache row is treated
	 * as "user has an empty draft" and skipped — local intent always
	 * wins over server snapshot.
	 */
	async init(opts: { cache: Cache; gameId: string }): Promise<void> {
		this.cache = opts.cache;
		this.gameId = opts.gameId;
		try {
			const stored = await opts.cache.get<OrderCommand[]>(
				NAMESPACE,
				draftKey(opts.gameId),
			);
			if (this.destroyed) return;
			if (stored === undefined) {
				this.commands = [];
				this.needsServerHydration = true;
			} else {
				this.commands = Array.isArray(stored) ? [...stored] : [];
				this.needsServerHydration = false;
			}
			this.recomputeStatuses();
			this.status = "ready";
		} catch (err) {
			if (this.destroyed) return;
			this.status = "error";
			this.error = err instanceof Error ? err.message : "load failed";
		}
	}

	/**
	 * hydrateFromServer fetches the player's stored order from the
	 * gateway when the cache row was absent at boot. The result is
	 * merged into `commands` and persisted so subsequent reloads
	 * prefer the cached version. Failures are non-fatal — the draft
	 * stays empty and the user can keep composing.
	 */
	async hydrateFromServer(opts: {
		client: GalaxyClient;
		turn: number;
	}): Promise<void> {
		if (this.status !== "ready" || !this.needsServerHydration) return;
		this.needsServerHydration = false;
		try {
			const fetched = await fetchOrder(opts.client, this.gameId, opts.turn);
			if (this.destroyed) return;
			this.commands = fetched.commands;
			this.updatedAt = fetched.updatedAt;
			this.recomputeStatuses();
			await this.persist();
		} catch (err) {
			if (this.destroyed) return;
			console.warn(
				"order-draft: server hydration failed; staying on empty draft",
				err,
			);
		}
	}

	/**
	 * add appends a command to the end of the draft, runs local
	 * validation for the new entry, and persists the updated list.
	 * Mutations made before `init` resolves are ignored — the layout
	 * always awaits `init` before exposing the store.
	 */
	async add(command: OrderCommand): Promise<void> {
		if (this.status !== "ready") return;
		this.commands = [...this.commands, command];
		this.statuses = { ...this.statuses, [command.id]: validateCommand(command) };
		await this.persist();
	}

	/**
	 * remove drops the command with the given id from the draft and
	 * persists the result. A miss is a no-op.
	 */
	async remove(id: string): Promise<void> {
		if (this.status !== "ready") return;
		const next = this.commands.filter((cmd) => cmd.id !== id);
		if (next.length === this.commands.length) return;
		this.commands = next;
		const nextStatuses = { ...this.statuses };
		delete nextStatuses[id];
		this.statuses = nextStatuses;
		await this.persist();
	}

	/**
	 * move relocates the command at `fromIndex` to `toIndex`, shifting
	 * the intermediate commands. Out-of-range indices and identical
	 * positions are no-ops; both indices are clamped against the
	 * current `commands` length.
	 */
	async move(fromIndex: number, toIndex: number): Promise<void> {
		if (this.status !== "ready") return;
		const length = this.commands.length;
		if (fromIndex < 0 || fromIndex >= length) return;
		if (toIndex < 0 || toIndex >= length) return;
		if (fromIndex === toIndex) return;
		const next = [...this.commands];
		const [picked] = next.splice(fromIndex, 1);
		if (picked === undefined) return;
		next.splice(toIndex, 0, picked);
		this.commands = next;
		await this.persist();
	}

	/**
	 * markSubmitting flips the status of every entry in `ids` to
	 * `submitting` so the order tab can disable per-row controls and
	 * show a spinner. The state machine runs `valid → submitting →
	 * applied | rejected` (see ui/docs/order-composer.md).
	 */
	markSubmitting(ids: string[]): void {
		const next = { ...this.statuses };
		for (const id of ids) {
			next[id] = "submitting";
		}
		this.statuses = next;
	}

	/**
	 * applyResults merges the verdict map returned by `submitOrder`
	 * into the per-command status map. Entries not present in the
	 * map keep their current status — useful when only a subset of
	 * commands round-tripped to the server. The engine-assigned
	 * `updatedAt` is also stashed for the next submit's stale-order
	 * detection (kept as plumbing only in Phase 14).
	 */
	applyResults(opts: {
		results: Map<string, CommandStatus>;
		updatedAt: number;
	}): void {
		const next = { ...this.statuses };
		for (const [id, status] of opts.results.entries()) {
			next[id] = status;
		}
		this.statuses = next;
		this.updatedAt = opts.updatedAt;
	}

	/**
	 * markRejected switches every supplied id to `rejected`. Used by
	 * the order tab when `submitOrder` returns `ok: false` — the
	 * gateway didn't process any command, so the entire batch is
	 * treated as rejected.
	 */
	markRejected(ids: string[]): void {
		const next = { ...this.statuses };
		for (const id of ids) {
			next[id] = "rejected";
		}
		this.statuses = next;
	}

	/**
	 * revertSubmittingToValid resets every entry currently in
	 * `submitting` back to its pre-submit status (typically `valid`).
	 * Called when the network layer throws an exception so the
	 * operator can retry without the rows looking stuck mid-flight.
	 */
	revertSubmittingToValid(): void {
		const next = { ...this.statuses };
		for (const cmd of this.commands) {
			if (next[cmd.id] === "submitting") {
				next[cmd.id] = validateCommand(cmd);
			}
		}
		this.statuses = next;
	}

	dispose(): void {
		this.destroyed = true;
		this.cache = null;
	}

	private recomputeStatuses(): void {
		const next: Record<string, CommandStatus> = {};
		for (const cmd of this.commands) {
			next[cmd.id] = validateCommand(cmd);
		}
		this.statuses = next;
	}

	private async persist(): Promise<void> {
		if (this.cache === null || this.destroyed) return;
		// `commands` is `$state`, so individual entries are proxies.
		// IndexedDB's structured clone refuses to clone proxies, so the
		// snapshot must be taken before the put.
		const snapshot = $state.snapshot(this.commands) as OrderCommand[];
		await this.cache.put(NAMESPACE, draftKey(this.gameId), snapshot);
	}
}

function validateCommand(cmd: OrderCommand): CommandStatus {
	switch (cmd.kind) {
		case "planetRename":
			return validateEntityName(cmd.name).ok ? "valid" : "invalid";
		case "placeholder":
			// Phase 12 placeholder entries are content-free and never
			// transition out of `draft` — they are not submittable.
			return "draft";
	}
}