import * as vscode from 'vscode';
import * as fs from 'fs';
import * as path from 'path';
import { ChatMessage } from '../agent';
import { logInfo, logError } from '../utils';

interface SessionData {
    taskId: string;
    history: ChatMessage[];
    lastActionStr?: string;
    timestamp: number;
}

export class SessionManager {
    private sessionDir: string;

    constructor(private context: vscode.ExtensionContext) {
        // Use globalStorageUri for persistence across workspace restarts
        this.sessionDir = path.join(this.context.globalStorageUri.fsPath, 'sessions');
        this.ensureDir(this.sessionDir);
    }

    private ensureDir(dir: string) {
        if (!fs.existsSync(dir)) {
            fs.mkdirSync(dir, { recursive: true });
        }
    }

    /**
     * Saves the current session state.
     */
    public async saveSession(taskId: string, history: ChatMessage[], lastActionStr?: string) {
        const sessionData: SessionData = {
            taskId,
            history,
            lastActionStr,
            timestamp: Date.now()
        };

        const filePath = path.join(this.sessionDir, `session_${this.sanitizeFilename(taskId)}.json`);
        try {
            fs.writeFileSync(filePath, JSON.stringify(sessionData, null, 2), 'utf-8');
            // Also store the last active taskId in globalState
            await this.context.globalState.update('activeTaskId', taskId);
        } catch (error: any) {
            logError('Failed to save session state', error);
        }
    }

    /**
     * Loads a specific session by taskId.
     */
    public loadSession(taskId: string): SessionData | null {
        const filePath = path.join(this.sessionDir, `session_${this.sanitizeFilename(taskId)}.json`);
        if (!fs.existsSync(filePath)) return null;

        try {
            const content = fs.readFileSync(filePath, 'utf-8');
            return JSON.parse(content) as SessionData;
        } catch (error: any) {
            logError(`Failed to load session for taskId: ${taskId}`, error);
            return null;
        }
    }

    /**
     * Loads the last active session.
     */
    public loadLastActiveSession(): SessionData | null {
        const lastTaskId = this.context.globalState.get<string>('activeTaskId');
        if (!lastTaskId) return null;
        return this.loadSession(lastTaskId);
    }

    /**
     * Clears a specific session.
     */
    public clearSession(taskId: string) {
        const filePath = path.join(this.sessionDir, `session_${this.sanitizeFilename(taskId)}.json`);
        if (fs.existsSync(filePath)) {
            fs.unlinkSync(filePath);
        }
    }

    private sanitizeFilename(name: string): string {
        return name.replace(/[^a-z0-9]/gi, '_').toLowerCase();
    }
}