add persistent chat history with cross-device sync

1 files changed, 136 insertions, 0 deletions

diff --git a/src/chat-history.ts b/src/chat-history.ts
new file mode 100644
index 0000000..ac29ed9
--- /dev/null
+++ b/src/chat-history.ts
@@ -0,0 +1,136 @@
+import type { App } from "obsidian";
+import type { ChatMessage } from "./ollama-client";
+
+/**
+ * Stored chat history format.
+ * Only user and assistant messages are persisted — system and tool messages
+ * are transient (injected per-request by the agent loop).
+ */
+export interface ChatHistoryData {
+	version: 1;
+	messages: PersistedMessage[];
+}
+
+/**
+ * A message stored in the chat history file.
+ * This is a subset of ChatMessage — we strip tool_calls, tool_name,
+ * and system/tool role messages since they are not meaningful across sessions.
+ */
+export interface PersistedMessage {
+	role: "user" | "assistant";
+	content: string;
+}
+
+const CHAT_HISTORY_FILENAME = "chat-history.json";
+
+/**
+ * Resolve the full path to the chat history file inside the plugin folder.
+ */
+function getHistoryPath(app: App, pluginId: string): string {
+	return `${app.vault.configDir}/plugins/${pluginId}/${CHAT_HISTORY_FILENAME}`;
+}
+
+/**
+ * Filter ChatMessage[] down to only persistable user/assistant messages.
+ */
+export function toPersistableMessages(messages: readonly ChatMessage[]): PersistedMessage[] {
+	const result: PersistedMessage[] = [];
+	for (const msg of messages) {
+		if (msg.role === "user" || msg.role === "assistant") {
+			result.push({ role: msg.role, content: msg.content });
+		}
+	}
+	return result;
+}
+
+/**
+ * Convert persisted messages back to ChatMessage[] for the LLM context.
+ */
+export function toRuntimeMessages(messages: readonly PersistedMessage[]): ChatMessage[] {
+	return messages.map((m) => ({ role: m.role, content: m.content }));
+}
+
+/**
+ * Load chat history from the plugin folder.
+ * Returns an empty array if the file doesn't exist or is corrupted.
+ */
+export async function loadChatHistory(app: App, pluginId: string): Promise<PersistedMessage[]> {
+	const path = getHistoryPath(app, pluginId);
+
+	try {
+		const exists = await app.vault.adapter.exists(path);
+		if (!exists) {
+			return [];
+		}
+
+		const raw = await app.vault.adapter.read(path);
+		const parsed = JSON.parse(raw) as unknown;
+
+		if (!isValidChatHistory(parsed)) {
+			return [];
+		}
+
+		return parsed.messages;
+	} catch {
+		return [];
+	}
+}
+
+/**
+ * Save chat history to the plugin folder.
+ */
+export async function saveChatHistory(
+	app: App,
+	pluginId: string,
+	messages: readonly ChatMessage[],
+): Promise<void> {
+	const path = getHistoryPath(app, pluginId);
+	const persistable = toPersistableMessages(messages);
+
+	const data: ChatHistoryData = {
+		version: 1,
+		messages: persistable,
+	};
+
+	await app.vault.adapter.write(path, JSON.stringify(data, null, 2));
+}
+
+/**
+ * Clear the chat history by writing an empty messages array.
+ * Writing an empty file rather than deleting ensures Obsidian Sync
+ * propagates the "cleared" state to all devices.
+ */
+export async function clearChatHistory(app: App, pluginId: string): Promise<void> {
+	const path = getHistoryPath(app, pluginId);
+
+	const data: ChatHistoryData = {
+		version: 1,
+		messages: [],
+	};
+
+	try {
+		await app.vault.adapter.write(path, JSON.stringify(data, null, 2));
+	} catch {
+		// Silently ignore — clear is best-effort
+	}
+}
+
+/**
+ * Type guard for validating the parsed chat history JSON.
+ */
+function isValidChatHistory(value: unknown): value is ChatHistoryData {
+	if (typeof value !== "object" || value === null) return false;
+
+	const obj = value as Record<string, unknown>;
+	if (obj["version"] !== 1) return false;
+	if (!Array.isArray(obj["messages"])) return false;
+
+	for (const msg of obj["messages"]) {
+		if (typeof msg !== "object" || msg === null) return false;
+		const m = msg as Record<string, unknown>;
+		if (m["role"] !== "user" && m["role"] !== "assistant") return false;
+		if (typeof m["content"] !== "string") return false;
+	}
+
+	return true;
+}