src/pages/api/sql.ts

import { HfInference } from "@huggingface/inference";
import { NextApiRequest, NextApiResponse } from "next";
import { createConnection, executeQuery } from "@/utils/database";

export default async function handler(
  req: NextApiRequest,
  res: NextApiResponse
) {
  if (req.method !== "POST") {
    return res.status(405).json({ message: "Method not allowed" });
  }

  const { dbUri, userPrompt } = req.body;

  if (!dbUri || !userPrompt) {
    return res.status(400).json({ 
      message: "Missing required fields", 
      details: {
        dbUri: !dbUri ? "Database URI is required" : null,
        userPrompt: !userPrompt ? "Query prompt is required" : null
      }
    });
  }

  try {
    const apiKey = process.env.HUGGINGFACE_API_KEY;
    if (!apiKey) {
      return res.status(500).json({ 
        message: "Server configuration error", 
        details: "API key is not configured"
      });
    }

    let hf;
    try {
      hf = new HfInference(apiKey);
    } catch (error: any) {
      return res.status(500).json({ 
        message: "Failed to initialize AI model",
        details: error.message
      });
    }

    let response;
    const prompt = `You are a SQL expert. Convert the following text to a SQL query.
Rules:
- Return a JSON object with exactly this format: {"query": "YOUR SQL QUERY HERE", "chartType": "CHART TYPE HERE"}
- For chartType use one of: "bar", "pie", "line", "doughnut", or null
- The query should be safe and only return the requested data
- Keep table names exactly as provided
- Do not include any explanations or comments

Example input: "Show me sales data as a pie chart"
Example output: {"query": "SELECT * FROM sales LIMIT 10", "chartType": "pie"}

Text: ${userPrompt}`;

    try {
      response = await hf.chatCompletion({
        model: "nvidia/Llama-3.1-Nemotron-70B-Instruct-HF",
        messages: [{ role: "user", content: prompt }],
        temperature: 0.1,
        max_tokens: 500,
      });
      console.log(response);
    } catch (error: any) {
      console.log(error);
      return res.status(500).json({ 
        message: "AI model error",
        details: error.message || "Failed to generate SQL query"
      });
    }

    let sqlQuery = '';
    let requestedChartType = null;
    try {
      const content = response?.choices?.[0]?.message?.content?.trim() || '';
      
      const jsonMatch = content.match(/\{.*\}/s);
      if (jsonMatch) {
        const parsedResponse = JSON.parse(jsonMatch[0]);
        sqlQuery = parsedResponse.query?.trim();
        requestedChartType = parsedResponse.chartType;
      } else {
        sqlQuery = content
          .replace(/```sql/gi, '')
          .replace(/```/gi, '')
          .replace(/sql query:?\s*/gi, '')
          .replace(/query:?\s*/gi, '')
          .trim();
      }

      if (!sqlQuery) {
        throw new Error('No valid SQL query found in response');
      }
    } catch (error: any) {
      return res.status(500).json({ 
        message: "Failed to parse AI response",
        details: error.message
      });
    }

    let connection;
    try {
      connection = await createConnection(dbUri);
    } catch (error: any) {
      return res.status(500).json({ 
        message: "Database connection error",
        details: error.message
      });
    }

    try {
      const results = await executeQuery(connection, sqlQuery || '');
      
      let visualization = null;
      if (Array.isArray(results) && results.length > 0) {
        const firstRow = results[0];
        const columns = Object.keys(firstRow);
        
        const dataAnalysis = {
          totalColumns: columns.length,
          numericColumns: columns.filter(col => 
            typeof firstRow[col] === 'number' && 
            !col.toLowerCase().includes('id') && 
            !col.toLowerCase().includes('_id')
          ),
          dateColumns: columns.filter(col => firstRow[col] instanceof Date),
          stringColumns: columns.filter(col => 
            typeof firstRow[col] === 'string' ||
            col.toLowerCase().includes('name') ||
            col.toLowerCase().includes('title')
          ),
          rowCount: results.length
        };

        if (requestedChartType === 'pie' || requestedChartType === 'doughnut') {
          const preferredNumericColumns = dataAnalysis.numericColumns.filter(col => 
            col.toLowerCase().includes('status') ||
            col.toLowerCase().includes('count') ||
            col.toLowerCase().includes('amount') ||
            col.toLowerCase().includes('total')
          );
          
          if (preferredNumericColumns.length > 0) {
            dataAnalysis.numericColumns = preferredNumericColumns;
          }
        }

        if (requestedChartType) {
          switch (requestedChartType) {
            case 'pie':
            case 'doughnut':
              if (dataAnalysis.numericColumns.length > 0) {
                visualization = {
                  type: requestedChartType,
                  config: {
                    labels: results.map(row => 
                      dataAnalysis.stringColumns[0] 
                        ? String(row[dataAnalysis.stringColumns[0]]) 
                        : `Row ${results.indexOf(row) + 1}`
                    ),
                    datasets: [{
                      data: results.map(row => row[dataAnalysis.numericColumns[0]]),
                      backgroundColor: results.map(() => 
                        `hsla(${Math.random() * 360}, 70%, 50%, 0.6)`
                      )
                    }]
                  }
                };
              }
              break;

            case 'line':
              if (dataAnalysis.dateColumns.length > 0 || dataAnalysis.numericColumns.length > 0) {
                visualization = {
                  type: 'line',
                  config: {
                    labels: dataAnalysis.dateColumns.length > 0 
                      ? results.map(row => new Date(row[dataAnalysis.dateColumns[0]]).toLocaleDateString())
                      : results.map((_, idx) => `Point ${idx + 1}`),
                    datasets: dataAnalysis.numericColumns.map(col => ({
                      label: col,
                      data: results.map(row => row[col]),
                      borderColor: `hsl(${Math.random() * 360}, 70%, 50%)`,
                      tension: 0.1
                    }))
                  }
                };
              }
              break;

            case 'bar':
            default:
              visualization = {
                type: 'bar',
                config: {
                  labels: dataAnalysis.stringColumns.length > 0
                    ? results.map(row => String(row[dataAnalysis.stringColumns[0]]))
                    : results.map((_, idx) => `Row ${idx + 1}`),
                  datasets: dataAnalysis.numericColumns.map(col => ({
                    label: col,
                    data: results.map(row => row[col]),
                    backgroundColor: `hsla(${Math.random() * 360}, 70%, 50%, 0.6)`,
                    borderColor: `hsl(${Math.random() * 360}, 70%, 50%)`,
                    borderWidth: 1
                  }))
                }
              };
              break;
          }
        }
      }

      await connection.end();
      return res.status(200).json({ 
        results, 
        query: sqlQuery,
        visualization 
      });
    } catch (error: any) {
      await connection?.end();
      return res.status(500).json({ 
        message: "Query execution error",
        details: error.message
      });
    }

  } catch (error: any) {
    console.error('Unexpected API Error:', error);
    return res.status(500).json({ 
      message: "Unexpected error occurred", 
      details: error.message || "Unknown error"
    });
  }
}