import { Message, Skill, ToolDefinition, AgentConfig } from '../types';
import { formatDate } from '../utils/helpers';

/**
 * Context builder for constructing prompts
 */
export class ContextBuilder {
  private config: AgentConfig;

  constructor(config: AgentConfig) {
    this.config = config;
  }

  /**
   * Build system prompt with skills and tools
   */
  buildSystemPrompt(skills: Skill[], tools: ToolDefinition[]): string {
    const parts: string[] = [];

    // Add base system prompt
    if (this.config.systemPrompt) {
      parts.push(this.config.systemPrompt);
    } else {
      parts.push(this.getDefaultSystemPrompt());
    }

    // Add current time
    parts.push(`\nCurrent time: ${formatDate(new Date())}`);

    // Add skills information
    if (skills.length > 0) {
      parts.push('\n## Available Skills');
      parts.push(
        'You have access to the following skills that provide additional context and capabilities:\n'
      );
      for (const skill of skills) {
        parts.push(`### ${skill.name}`);
        parts.push(skill.description);
        parts.push('');
      }
    }

    // Add tools information
    if (tools.length > 0) {
      parts.push('\n## Available Tools');
      parts.push('You can use the following tools to perform actions:\n');
      for (const tool of tools) {
        parts.push(`- **${tool.function.name}**: ${tool.function.description}`);
      }
      parts.push('');
    }

    return parts.join('\n');
  }

  /**
   * Get default system prompt
   */
  private getDefaultSystemPrompt(): string {
    return `You are a helpful AI assistant powered by planck-claw. You are knowledgeable, precise, and aim to be helpful.

Your capabilities:
- Answer questions accurately and concisely
- Execute tasks using available tools
- Remember context from the conversation
- Use skills to enhance your knowledge and capabilities

Guidelines:
- Be honest if you don't know something
- Use tools when they can help accomplish the task
- Keep responses clear and well-structured
- Respect user privacy and security`;
  }

  /**
   * Build context messages for LLM
   */
  buildContextMessages(
    conversationMessages: Message[],
    skills: Skill[],
    tools: ToolDefinition[]
  ): Message[] {
    const messages: Message[] = [];

    // Add system message with full context
    const systemPrompt = this.buildSystemPrompt(skills, tools);
    messages.push({
      role: 'system',
      content: systemPrompt,
    });

    // Add conversation history
    messages.push(...conversationMessages);

    return messages;
  }

  /**
   * Format tool result for display
   */
  formatToolResult(toolName: string, result: string): string {
    return `[Tool: ${toolName}]\n${result}`;
  }

  /**
   * Truncate context if too long
   */
  truncateContext(messages: Message[], maxLength: number): Message[] {
    // Always keep system message
    const systemMessages = messages.filter((m) => m.role === 'system');
    const otherMessages = messages.filter((m) => m.role !== 'system');

    // Calculate total length
    let totalLength = 0;
    for (const msg of messages) {
      totalLength += msg.content.length;
    }

    if (totalLength <= maxLength) {
      return messages;
    }

    // Keep recent messages that fit within limit
    const recentMessages: Message[] = [];
    let currentLength = systemMessages.reduce((sum, m) => sum + m.content.length, 0);

    // If system messages alone exceed maxLength, return only system messages
    if (currentLength >= maxLength) {
      return systemMessages;
    }

    for (let i = otherMessages.length - 1; i >= 0; i--) {
      const msg = otherMessages[i];
      if (currentLength + msg.content.length > maxLength) {
        break;
      }
      recentMessages.unshift(msg);
      currentLength += msg.content.length;
    }

    return [...systemMessages, ...recentMessages];
  }
}