Initial cache implementation

Source/SwiftLintFramework/Models/LinterCache.swift

@@ -0,0 +1,86 @@
+//
+//  LinterCache.swift
+//  SwiftLint
+//
+//  Created by Marcelo Fabri on 12/27/16.
+//  Copyright © 2016 Realm. All rights reserved.
+//
+
+import Foundation
+import SourceKittenFramework
+
+public struct LinterCache {
+    private var cache = [String: [String: Any]]()
+
+    public init() { }
+
+    public init(contentsOf url: URL) throws {
+        let data = try Data(contentsOf: url)
+        let json = try JSONSerialization.jsonObject(with: data, options: [])
+        if let json = json as? [String: [String: Any]] {
+            cache = json
+        }
+    }
+
+    public mutating func cacheFile(_ file: String, violations: [StyleViolation], hash: Int) {
+
+        var entry = [String: Any]()
+        var fileViolations = entry["violations"] as? [[String: Any]] ?? []
+
+        for violation in violations {
+            fileViolations.append(dictionaryForViolation(violation))
+        }
+
+        entry["violations"] = fileViolations
+        entry["hash"] = hash
+        cache[file] = entry
+    }
+
+    public func violations(for file: String, hash: Int) -> [StyleViolation]? {
+        guard let entry = cache[file],
+            let cacheHash = entry["hash"] as? Int,
+            cacheHash == hash,
+            let violations = entry["violations"] as? [[String: Any]] else {
+            return nil
+        }
+
+        return violations.flatMap { StyleViolation.fromCache($0, file: file) }
+    }
+
+    public func save(to url: URL) throws {
+        let json = toJSON(cache)
+        try json.write(to: url, atomically: true, encoding: .utf8)
+    }
+
+    private func dictionaryForViolation(_ violation: StyleViolation) -> [String: Any] {
+        return [
+            "line": violation.location.line ?? NSNull() as Any,
+            "character": violation.location.character ?? NSNull() as Any,
+            "severity": violation.severity.rawValue,
+            "type": violation.ruleDescription.name,
+            "rule_id": violation.ruleDescription.identifier,
+            "reason": violation.reason
+        ]
+    }
+}
+
+extension StyleViolation {
+    fileprivate static func fromCache(_ cache: [String: Any], file: String) -> StyleViolation? {
+        guard let severity = (cache["severity"] as? String).flatMap(ViolationSeverity.init),
+            let name = cache["type"] as? String,
+            let ruleId = cache["rule_id"] as? String,
+            let reason = cache["reason"] as? String else {
+                return nil
+        }
+
+        let line = cache["line"] as? Int
+        let character = cache["character"] as? Int
+
+        let ruleDescription = RuleDescription(identifier: ruleId, name: name, description: reason)
+        let location = Location(file: file, line: line, character: character)
+        let violation = StyleViolation(ruleDescription: ruleDescription, severity: severity,
+                                       location: location, reason: reason)
+
+        return violation
+    }
+}

Source/SwiftLintFramework/Models/ViolationSeverity.swift

@@ -9,6 +9,10 @@
 public enum ViolationSeverity: String, Comparable {
     case warning
     case error
+
+    public init?(identifier: String) {
+        self.init(rawValue: identifier)
+    }
 }
 
 // MARK: Comparable