/**
 * ESLint rule to enforce single export per file
 * 
 * Each file should export exactly one named export (or default export).
 * This ensures clear, focused modules.
 */

module.exports = {
  meta: {
    type: 'problem',
    docs: {
      description: 'Enforce single export per file',
      category: 'Best Practices',
      recommended: true,
    },
    fixable: null,
    schema: [],
    messages: {
      multipleExports: 'File should have exactly one export. Found {{count}} exports: {{exports}}',
      noExports: 'File should have at least one export',
    },
  },

  create(context) {
    let exportCount = 0;
    const exportNames = [];

    return {
      // Track named exports
      ExportNamedDeclaration(node) {
        if (node.declaration) {
          // Exporting a class, function, const, etc.
          if (node.declaration.id) {
            exportCount++;
            exportNames.push(node.declaration.id.name);
          } else if (node.declaration.declarations) {
            // Multiple const exports
            node.declaration.declarations.forEach(decl => {
              if (decl.id && decl.id.name) {
                exportCount++;
                exportNames.push(decl.id.name);
              }
            });
          }
        } else if (node.specifiers) {
          // Re-exports
          node.specifiers.forEach(spec => {
            exportCount++;
            exportNames.push(spec.exported.name);
          });
        }
      },

      // Track default exports
      ExportDefaultDeclaration(node) {
        exportCount++;
        if (node.declaration && node.declaration.id) {
          exportNames.push(`default (${node.declaration.id.name})`);
        } else {
          exportNames.push('default');
        }
      },

      'Program:exit'() {
        if (exportCount === 0) {
          context.report({
            node: context.getSourceCode().ast,
            messageId: 'noExports',
          });
        } else if (exportCount > 1) {
          context.report({
            node: context.getSourceCode().ast,
            messageId: 'multipleExports',
            data: {
              count: exportCount,
              exports: exportNames.join(', '),
            },
          });
        }
      },
    };
  },
};