const AWS = require('aws-sdk');
const dynamodb = new AWS.DynamoDB.DocumentClient();
const { v4: uuidv4 } = require('uuid');

const TABLE_NAME = process.env.TABLE_NAME;

// CORS headers
const headers = {
  'Content-Type': 'application/json',
  'Access-Control-Allow-Origin': process.env.CORS_ORIGIN || '*',
  'Access-Control-Allow-Headers': 'Content-Type,Authorization,X-Amz-Date,X-Api-Key,X-Amz-Security-Token',
  'Access-Control-Allow-Methods': 'GET,POST,PUT,DELETE,OPTIONS',
  'Access-Control-Allow-Credentials': 'true'
};

// Helper function to create response
const createResponse = (statusCode, body) => ({
  statusCode,
  headers,
  body: JSON.stringify(body)
});

// Helper to transform new structure to legacy format for backwards compatibility
const transformToLegacy = (item) => {
  if (item._legacy) {
    // New structure - extract legacy fields
    return {
      id: item.id,
      brand: item.brand,
      tip: item._legacy.tip || item.type || item.material?.base,
      finish: item._legacy.finish || item.material?.modifier || 'Basic',
      boja: item._legacy.boja || item.color?.name,
      refill: item._legacy.refill || (item.condition?.isRefill ? 'Da' : ''),
      vakum: item._legacy.vakum || (item.condition?.storageCondition === 'vacuum' ? 'vakuum' : ''),
      otvoreno: item._legacy.otvoreno || (item.condition?.storageCondition === 'opened' ? 'otvorena' : ''),
      kolicina: item._legacy.kolicina || String(item.inventory?.total || ''),
      cena: item._legacy.cena || String(item.pricing?.purchasePrice || ''),
      status: item._legacy.status,
      createdAt: item.createdAt,
      updatedAt: item.updatedAt
    };
  }
  // Already in legacy format
  return item;
};

// GET all filaments or filter by query params
const getFilaments = async (event) => {
  try {
    const queryParams = event.queryStringParameters || {};
    
    let params = {
      TableName: TABLE_NAME
    };

    // Support both old and new query parameters
    const brand = queryParams.brand;
    const materialBase = queryParams.material || queryParams.tip;
    const storageCondition = queryParams.storageCondition || queryParams.status;

    // Filter by brand
    if (brand) {
      params = {
        ...params,
        IndexName: 'brand-index',
        KeyConditionExpression: 'brand = :brand',
        ExpressionAttributeValues: {
          ':brand': brand
        }
      };
    }
    // Filter by material (supports old 'tip' param)
    else if (materialBase) {
      // Try new index first, fall back to old
      try {
        params = {
          ...params,
          IndexName: 'material-base-index',
          KeyConditionExpression: '#mb = :mb',
          ExpressionAttributeNames: {
            '#mb': 'material.base'
          },
          ExpressionAttributeValues: {
            ':mb': materialBase
          }
        };
      } catch (e) {
        // Fall back to old index
        params = {
          ...params,
          IndexName: 'tip-index',
          KeyConditionExpression: 'tip = :tip',
          ExpressionAttributeValues: {
            ':tip': materialBase
          }
        };
      }
    }
    // Filter by storage condition
    else if (storageCondition) {
      params = {
        ...params,
        FilterExpression: '#sc = :sc',
        ExpressionAttributeNames: {
          '#sc': 'condition.storageCondition'
        },
        ExpressionAttributeValues: {
          ':sc': storageCondition
        }
      };
    }

    // Execute query or scan
    let result;
    if (params.IndexName || params.KeyConditionExpression) {
      result = await dynamodb.query(params).promise();
    } else {
      result = await dynamodb.scan(params).promise();
    }

    // Check if client supports new format
    const acceptsNewFormat = event.headers?.['X-Accept-Format'] === 'v2';
    
    if (acceptsNewFormat) {
      // Return new format
      return createResponse(200, result.Items);
    } else {
      // Transform to legacy format for backwards compatibility
      const legacyItems = result.Items.map(transformToLegacy);
      return createResponse(200, legacyItems);
    }
  } catch (error) {
    console.error('Error getting filaments:', error);
    return createResponse(500, { error: 'Failed to fetch filaments' });
  }
};

// GET single filament by ID
const getFilament = async (event) => {
  try {
    const { id } = event.pathParameters;
    
    const params = {
      TableName: TABLE_NAME,
      Key: { id }
    };

    const result = await dynamodb.get(params).promise();
    
    if (!result.Item) {
      return createResponse(404, { error: 'Filament not found' });
    }

    return createResponse(200, result.Item);
  } catch (error) {
    console.error('Error getting filament:', error);
    return createResponse(500, { error: 'Failed to fetch filament' });
  }
};

// Helper to generate SKU
const generateSKU = (brand, material, color) => {
  const brandCode = brand.substring(0, 3).toUpperCase();
  const materialCode = material.substring(0, 3).toUpperCase();
  const colorCode = color.substring(0, 3).toUpperCase();
  const random = Math.random().toString(36).substring(2, 5).toUpperCase();
  return `${brandCode}-${materialCode}-${colorCode}-${random}`;
};

// POST - Create new filament
const createFilament = async (event) => {
  try {
    const body = JSON.parse(event.body);
    const timestamp = new Date().toISOString();
    const acceptsNewFormat = event.headers?.['X-Accept-Format'] === 'v2';
    
    let item;
    
    if (acceptsNewFormat || body.material) {
      // New format
      item = {
        id: uuidv4(),
        sku: body.sku || generateSKU(body.brand, body.material.base, body.color.name),
        ...body,
        createdAt: timestamp,
        updatedAt: timestamp
      };
    } else {
      // Legacy format - convert to new structure
      const material = {
        base: body.tip || 'PLA',
        modifier: body.finish !== 'Basic' ? body.finish : null
      };
      
      const storageCondition = body.vakum?.toLowerCase().includes('vakuum') ? 'vacuum' : 
                               body.otvoreno?.toLowerCase().includes('otvorena') ? 'opened' : 'sealed';
      
      item = {
        id: uuidv4(),
        sku: generateSKU(body.brand, material.base, body.boja),
        brand: body.brand,
        type: body.tip || 'PLA',
        material: material,
        color: {
          name: body.boja,
          hex: null
        },
        weight: {
          value: 1000,
          unit: 'g'
        },
        diameter: 1.75,
        inventory: {
          total: parseInt(body.kolicina) || 1,
          available: storageCondition === 'opened' ? 0 : 1,
          inUse: 0,
          locations: {
            vacuum: storageCondition === 'vacuum' ? 1 : 0,
            opened: storageCondition === 'opened' ? 1 : 0,
            printer: 0
          }
        },
        pricing: {
          purchasePrice: body.cena ? parseFloat(body.cena) : null,
          currency: 'RSD'
        },
        condition: {
          isRefill: body.refill === 'Da',
          storageCondition: storageCondition
        },
        tags: [],
        _legacy: {
          tip: body.tip,
          finish: body.finish,
          boja: body.boja,
          refill: body.refill,
          vakum: body.vakum,
          otvoreno: body.otvoreno,
          kolicina: body.kolicina,
          cena: body.cena,
          status: body.status || 'new'
        },
        createdAt: timestamp,
        updatedAt: timestamp
      };
    }

    const params = {
      TableName: TABLE_NAME,
      Item: item
    };

    await dynamodb.put(params).promise();
    
    // Return in appropriate format
    const response = acceptsNewFormat ? item : transformToLegacy(item);
    return createResponse(201, response);
  } catch (error) {
    console.error('Error creating filament:', error);
    return createResponse(500, { error: 'Failed to create filament' });
  }
};

// PUT - Update filament
const updateFilament = async (event) => {
  try {
    const { id } = event.pathParameters;
    const body = JSON.parse(event.body);
    const timestamp = new Date().toISOString();
    
    // Determine status based on vakum and otvoreno fields
    let status = 'new';
    if (body.otvoreno && body.otvoreno.toLowerCase().includes('otvorena')) {
      status = 'opened';
    } else if (body.refill && body.refill.toLowerCase() === 'da') {
      status = 'refill';
    }

    const params = {
      TableName: TABLE_NAME,
      Key: { id },
      UpdateExpression: `SET 
        brand = :brand,
        tip = :tip,
        finish = :finish,
        boja = :boja,
        refill = :refill,
        vakum = :vakum,
        otvoreno = :otvoreno,
        kolicina = :kolicina,
        cena = :cena,
        #status = :status,
        updatedAt = :updatedAt`,
      ExpressionAttributeNames: {
        '#status': 'status'
      },
      ExpressionAttributeValues: {
        ':brand': body.brand,
        ':tip': body.tip,
        ':finish': body.finish,
        ':boja': body.boja,
        ':refill': body.refill,
        ':vakum': body.vakum,
        ':otvoreno': body.otvoreno,
        ':kolicina': body.kolicina,
        ':cena': body.cena,
        ':status': status,
        ':updatedAt': timestamp
      },
      ReturnValues: 'ALL_NEW'
    };

    const result = await dynamodb.update(params).promise();
    return createResponse(200, result.Attributes);
  } catch (error) {
    console.error('Error updating filament:', error);
    return createResponse(500, { error: 'Failed to update filament' });
  }
};

// DELETE filament
const deleteFilament = async (event) => {
  try {
    const { id } = event.pathParameters;
    
    const params = {
      TableName: TABLE_NAME,
      Key: { id }
    };

    await dynamodb.delete(params).promise();
    return createResponse(200, { message: 'Filament deleted successfully' });
  } catch (error) {
    console.error('Error deleting filament:', error);
    return createResponse(500, { error: 'Failed to delete filament' });
  }
};

// Main handler
exports.handler = async (event) => {
  const { httpMethod, resource } = event;

  // Handle CORS preflight
  if (httpMethod === 'OPTIONS') {
    return createResponse(200, {});
  }

  // Route requests
  if (resource === '/filaments' && httpMethod === 'GET') {
    return getFilaments(event);
  } else if (resource === '/filaments' && httpMethod === 'POST') {
    return createFilament(event);
  } else if (resource === '/filaments/{id}' && httpMethod === 'GET') {
    return getFilament(event);
  } else if (resource === '/filaments/{id}' && httpMethod === 'PUT') {
    return updateFilament(event);
  } else if (resource === '/filaments/{id}' && httpMethod === 'DELETE') {
    return deleteFilament(event);
  }

  return createResponse(404, { error: 'Not found' });
};