import * as ts from 'typescript';
import * as Lint from 'tslint';

/**
 * A base walker class that gracefully handles unexpected errors.
 * Errors are often thrown when the TypeChecker is invoked.
 */
export class ErrorTolerantWalker extends Lint.RuleWalker {
    public static DEBUG: boolean = false;

    protected visitNode(node: ts.Node): void {
        try {
            super.visitNode(node);
        } catch (error) {
            // turn this on when trying out new rules on foreign codebases
            if (ErrorTolerantWalker.DEBUG) {
                const msg: string =
                    'An error occurred visiting a node.' +
                    '\nWalker: ' +
                    this.getClassName() +
                    '\nNode: ' +
                    (node.getFullText ? node.getFullText() : '<unknown>') +
                    '\n' +
                    error;

                this.addFailureAt(node.getStart ? node.getStart() : 0, node.getWidth ? node.getWidth() : 0, msg);
            }
        }
    }

    private getClassName(): string {
        // Some versions of IE have the word "function" in the constructor name and
        // have the function body there as well. This rips out and returns the function name.
        const result: string = this.constructor.toString().match(/function\s+([\w\$]+)\s*\(/)[1] || '';
        if (result == null || result.length === 0) {
            throw new Error('Could not determine class name from input: ' + this.constructor.toString());
        }
        return result;
    }
}