SwiftLint/Source/SwiftLintFramework/Rules/VerticalParameterAlignmentOnCallRule.swift

//
//  VerticalParameterAlignmentOnCallRule.swift
//  SwiftLint
//
//  Created by Marcelo Fabri on 02/05/17.
//  Copyright © 2017 Realm. All rights reserved.
//

import Foundation
import SourceKittenFramework

public struct VerticalParameterAlignmentOnCallRule: ASTRule, ConfigurationProviderRule, OptInRule {
    public var configuration = SeverityConfiguration(.warning)

    public init() {}

    public static let description = RuleDescription(
        identifier: "vertical_parameter_alignment_on_call",
        name: "Vertical Parameter Alignment On Call",
        description: "Function parameters should be aligned vertically if they're in multiple lines in a method call.",
        nonTriggeringExamples: [
            "foo(param1: 1, param2: bar\n" +
            "    param3: false, param4: true)",
            "foo(param1: 1, param2: bar)",
            "foo(param1: 1, param2: bar\n" +
            "    param3: false,\n" +
            "    param4: true)"
        ],
        triggeringExamples: [
            "foo(param1: 1, param2: bar\n" +
            "                ↓param3: false, param4: true)",
            "foo(param1: 1, param2: bar\n" +
            " ↓param3: false, param4: true)",
            "foo(param1: 1, param2: bar\n" +
            "       ↓param3: false,\n" +
            "       ↓param4: true)"
        ]
    )

    public func validate(file: File, kind: SwiftExpressionKind,
                         dictionary: [String: SourceKitRepresentable]) -> [StyleViolation] {
        guard kind == .call,
            case let arguments = dictionary.enclosedArguments,
            arguments.count > 1,
            let firstArgumentOffset = arguments.first?.offset,
            case let contents = file.contents.bridge(),
            let firstArgumentPosition = contents.lineAndCharacter(forByteOffset: firstArgumentOffset) else {
                return []
        }

        var visitedLines: Set<Int> = []
        let violatingOffsets: [Int] = arguments.dropFirst().flatMap { argument in
            guard let offset = argument.offset,
                let (line, character) = contents.lineAndCharacter(forByteOffset: offset),
                line > firstArgumentPosition.line else {
                    return nil
            }

            let (firstVisit, _) = visitedLines.insert(line)
            guard character != firstArgumentPosition.character && firstVisit else {
                return nil
            }

            return offset
        }

        return violatingOffsets.map {
            StyleViolation(ruleDescription: type(of: self).description,
                           severity: configuration.severity,
                           location: Location(file: file, byteOffset: $0))
        }
    }
}