Add commit lint implementation

Sources/DangerSwiftCommitLint/CommitChecker/BodyEmptyLine.swift

@@ -0,0 +1,15 @@
+import Foundation
+
+struct BodyEmptyLine: CommitLint, Hashable {
+    static var linterMessage = "Please separate commit message subject from body with newline."
+
+    private let bodyLinesOfText: [String]
+
+    init(_ commitMessage: GitCommitMessage) {
+        bodyLinesOfText = commitMessage.bodyLinesOfText
+    }
+
+    var fail: Bool {
+        bodyLinesOfText.isEmpty ? false : bodyLinesOfText.first?.isEmpty == false
+    }
+}

Sources/DangerSwiftCommitLint/CommitChecker/CommitLint.swift

@@ -0,0 +1,17 @@
+import Foundation
+
+public protocol CommitLint {
+    static var linterMessage: String { get }
+
+    var fail: Bool { get }
+
+    init(_ commitMessage: GitCommitMessage)
+
+    static func fail(_ commitMessage: GitCommitMessage) -> Bool
+}
+
+public extension CommitLint {
+    static func fail(_ commitMessage: GitCommitMessage) -> Bool {
+        Self(commitMessage).fail
+    }
+}

Sources/DangerSwiftCommitLint/CommitChecker/GitCommitMessage.swift

@@ -0,0 +1,31 @@
+import Danger
+import Foundation
+
+/// An abstraction of Git commit message for `DangerSwiftCommitLint`.
+public struct GitCommitMessage: Hashable {
+    /// First line of the commit message
+    public let subject: String
+    /// Rest of the commit message
+    public let bodyLinesOfText: [String]
+    // Commit SHA value
+    public let sha: String?
+
+    init(
+        subject: String,
+        bodyLinesOfText: [String],
+        sha: String
+    ) {
+        self.subject = subject
+        self.bodyLinesOfText = bodyLinesOfText
+        self.sha = sha
+    }
+
+    /// Initialize `GitCommitMessage` with `Danger.Git.Commit.message`
+    /// - Parameter gitCommit: An instance of `Danger.Git.Commit`
+    public init(_ gitCommit: Git.Commit) {
+        let commitMessageLines = gitCommit.message.components(separatedBy: .newlines)
+        subject = commitMessageLines.first ?? ""
+        bodyLinesOfText = Array(commitMessageLines.dropFirst())
+        sha = gitCommit.sha
+    }
+}

Sources/DangerSwiftCommitLint/CommitChecker/SubjectCapitalLetter.swift

@@ -0,0 +1,15 @@
+import Foundation
+
+struct SubjectCapitalLetter: CommitLint, Hashable {
+    static let linterMessage = "Please start commit message subject with capital letter."
+
+    private let firstCharacter: Character?
+
+    init(_ commitMessage: GitCommitMessage) {
+        firstCharacter = commitMessage.subject.first
+    }
+
+    var fail: Bool {
+        firstCharacter?.isLowercase ?? false
+    }
+}

Sources/DangerSwiftCommitLint/CommitChecker/SubjectLengthCheck.swift → Sources/DangerSwiftCommitLint/CommitChecker/SubjectLength.swift

@@ -1,25 +1,25 @@
 import Foundation
 
-struct SubjectLengthCheck: CommitChecker {
+struct SubjectLength: CommitLint, Hashable {
     private enum GeneratedSubjectPattern {
         static let git = #"^Merge branch '.+' into "#
         static let gitHub = #"^Merge pull request #\d+ from "#
     }
 
-    static let warningMessage = "Please limit commit message subject line to 50 characters."
+    static let linterMessage = "Please limit commit message subject line to 50 characters."
 
     private let subject: String
 
-    init(message: CommitMessage) {
-        subject = message.subject
+    init(_ commitMessage: GitCommitMessage) {
+        subject = commitMessage.subject
     }
 
     var fail: Bool {
         subject.count > 50 && isMergeCommit == false
     }
 }
 
-private extension SubjectLengthCheck {
+private extension SubjectLength {
     var isMergeCommit: Bool {
         subject =~ GeneratedSubjectPattern.git || subject =~ GeneratedSubjectPattern.gitHub
     }

Sources/DangerSwiftCommitLint/CommitChecker/SubjectPeriod.swift

@@ -0,0 +1,15 @@
+import Foundation
+
+struct SubjectPeriod: CommitLint, Hashable {
+    static var linterMessage = "Please remove period from end of commit message subject line."
+
+    private let subject: String
+
+    init(_ commitMessage: GitCommitMessage) {
+        subject = commitMessage.subject
+    }
+
+    var fail: Bool {
+        subject.last == "."
+    }
+}

Sources/DangerSwiftCommitLint/CommitChecker/SubjectWord.swift

@@ -0,0 +1,15 @@
+import Foundation
+
+struct SubjectWord: CommitLint, Hashable {
+    static var linterMessage = "Please use more than one word in commit message."
+
+    private let subject: String
+
+    init(_ commitMessage: GitCommitMessage) {
+        subject = commitMessage.subject
+    }
+
+    var fail: Bool {
+        subject.split(separator: " ").count < 2
+    }
+}

Sources/DangerSwiftCommitLint/Configuration.swift

@@ -0,0 +1,109 @@
+import Foundation
+
+public extension DangerSwiftCommitLint {
+    /// All commit checkers provided by `DangerSwiftCommitLint`
+    enum CommitCheckerType: CaseIterable, Hashable {
+        /// Commit subject and body are separated by an empty line (`CommitChecker/BodyEmptyLineCheck`)
+        case bodyEmptyLine
+        /// Commit subject begins with a capital letter (`CommitChecker/SubjectCapCheck`)
+        case subjectCapitalLetter
+        /// Commit subject is no longer than 50 characters (`CommitChecker/SubjectLengthCheck`)
+        case subjectLength
+        /// Commit subject does not end in a period (`CommitChecker/SubjectPeriodCheck`)
+        case subjectPeriod
+        /// Commit subject is more than one word (`CommitChecker/SubjectWordCheck`)
+        case subjectWord
+    }
+
+    /// Checker selection
+    enum CommitCheckerSelection {
+        /// Select all checkers
+        case all
+        /// Select a set of checkers
+        case selected(Set<CommitCheckerType>)
+    }
+
+    struct Configuration {
+        let limit: Int
+
+        private let disabled: CommitCheckerSelection
+        private let warn: CommitCheckerSelection
+        private let fail: CommitCheckerSelection
+        private let customCheckers: [CommitLint.Type]
+
+        /// Initialize the configuration.
+        /// - Parameters:
+        ///   - disabled: The selected checks to skip.
+        ///   - warn: The selected checks to warn on.
+        ///   - fail: The selected checks to fail on.
+        ///   - limit: The number of commits to check.
+        ///   - customCheckers: An array of custom checkers.
+        public init(
+            disabled: CommitCheckerSelection = .selected([]),
+            warn: CommitCheckerSelection = .selected([]),
+            fail: CommitCheckerSelection = .all,
+            limit: Int = 0,
+            customCheckers: [CommitLint.Type] = []
+        ) {
+            self.disabled = disabled
+            self.warn = warn
+            self.fail = fail
+            self.limit = limit
+            self.customCheckers = customCheckers
+        }
+    }
+}
+
+extension DangerSwiftCommitLint.Configuration {
+    static var defaultCheckers: [CommitLint.Type] {
+        DangerSwiftCommitLint.CommitCheckerType.allCases.map(\.type)
+    }
+
+    var allCheckers: [CommitLint.Type] {
+        Self.defaultCheckers + customCheckers
+    }
+
+    var disabledCheckers: [CommitLint.Type] {
+        switch disabled {
+        case .all:
+            return allCheckers
+        case let .selected(disabled):
+            return disabled.map(\.type)
+        }
+    }
+
+    var enabledCheckers: [CommitLint.Type] {
+        allCheckers.filter { checker in
+            disabledCheckers.contains { $0 == checker } == false
+        }
+    }
+
+    var warningCheckers: [CommitLint.Type] {
+        switch warn {
+        case .all:
+            return allCheckers
+        case let .selected(warningCheckers):
+            return enabledCheckers.filter { type in
+                warningCheckers.map(\.type).contains { $0 == type }
+            }
+        }
+    }
+
+    var failingCheckers: [CommitLint.Type] {
+        enabledCheckers.filter { type in
+            warningCheckers.contains { $0 == type } == false
+        }
+    }
+}
+
+private extension DangerSwiftCommitLint.CommitCheckerType {
+    var type: CommitLint.Type {
+        switch self {
+        case .bodyEmptyLine: return BodyEmptyLine.self
+        case .subjectCapitalLetter: return SubjectCapitalLetter.self
+        case .subjectLength: return SubjectCapitalLetter.self
+        case .subjectPeriod: return SubjectPeriod.self
+        case .subjectWord: return SubjectWord.self
+        }
+    }
+}