#!/usr/bin/env swift

import Foundation

final class ReleaseNotesCreator {
    
    func gitLogs(count: Int) -> [String] {
        
        let gitProcess = Process()
        gitProcess.executableURL = URL(fileURLWithPath: "/usr/bin/git")
        gitProcess.arguments = ["log", "-\(count)",
                                "--pretty=format:\"%h (%cn) %s\""]
        
        let gitPipe = Pipe()
        gitProcess.standardOutput = gitPipe
        
        do {
            try gitProcess.run()
            gitProcess.waitUntilExit()
            
            let data = gitPipe.fileHandleForReading.readDataToEndOfFile()
            if let output = String(data: data, encoding: String.Encoding.utf8) { return output.components(separatedBy: "\n") }
        } catch { }
        
        return []
    }
    
    func write(notes: [String], to filePath: String, anchor: String) {
        
        let data = try! Data(contentsOf: URL(string: "file://\(filePath)")!)
        let content = String(decoding: data, as: UTF8.self)
        var lines = content.components(separatedBy: "\n")
        
        guard let index = lines.firstIndex(of: anchor) else { return }
        
        var result = [String]()
        result.append("<h3>GitLab updates</h3>")
        result.append("<h2>Commits</h2>")
        notes.forEach { result.append("<li>\($0.replacingOccurrences(of: "\"", with: ""))</li>") }
        result.append("<ul>")
        result.append("</ul>")
        
        lines.insert(contentsOf: result, at: index + 1)
        
        let resultString = lines.joined(separator: "\n")
        let resultData = resultString.data(using: .utf8)!
        
        try? resultData.write(to: URL(string: "file://\(filePath)")!)
        
    }
    
}

func showHelp() {
    print("How to use:")
    print("--path=[PATH TO RELEASE NOTES]")
}

guard let argument = CommandLine.arguments.first(where: { $0.contains("path") })
      , let path = argument.split(separator: "=").last else {
    showHelp()
    exit(1)
}

let rc = ReleaseNotesCreator()
let logs = rc.gitLogs(count: 10)
rc.write(notes: logs, to: String(path), anchor: "<div id=\"release\">")

exit(0)