import Foundation

enum TitleAnalysisEngine {
    static func analyze(title: String, goal: TitleGoal) -> TitleAnalysis {
        let length = title.count
        let lengthScore = scoreLength(length)
        let engagementScore = scoreEngagement(title, goal: goal)
        let clarityScore = scoreClarity(title)
        let overall = (lengthScore + engagementScore + clarityScore) / 3
        let suggestions = makeSuggestions(title: title, length: length, goal: goal)

        return TitleAnalysis(
            overallScore: overall,
            lengthScore: lengthScore,
            engagementScore: engagementScore,
            clarityScore: clarityScore,
            suggestions: suggestions
        )
    }

    private static func scoreLength(_ length: Int) -> Int {
        switch length {
        case 0: 0
        case 1...50: 95
        case 51...80: 85
        case 81...120: 70
        case 121...200: 50
        case 201...300: 30
        default: 10
        }
    }

    private static func scoreEngagement(_ title: String, goal: TitleGoal) -> Int {
        var score = 50
        let lower = title.lowercased()

        if title.contains("?") { score += 10 }
        if title.range(of: #"\d+"#, options: .regularExpression) != nil { score += 8 }
        if lower.contains("how") || lower.contains("why") || lower.contains("what") { score += 6 }
        if lower.contains("you") || lower.contains("your") { score += 5 }
        if title == title.uppercased() && title.count > 5 { score -= 15 }

        switch goal {
        case .question where !title.contains("?"): score -= 10
        case .listicle where title.range(of: #"\d+"#, options: .regularExpression) == nil: score -= 8
        case .curiosity where !lower.contains("secret") && !lower.contains("nobody") && !lower.contains("actually"): score -= 3
        default: break
        }

        return min(100, max(0, score))
    }

    private static func scoreClarity(_ title: String) -> Int {
        var score = 70
        let words = title.split(separator: " ").count

        if words >= 4 && words <= 12 { score += 15 }
        if words < 3 { score -= 20 }
        if words > 20 { score -= 15 }
        if title.contains("  ") { score -= 5 }
        if title.hasPrefix(" ") || title.hasSuffix(" ") { score -= 10 }

        return min(100, max(0, score))
    }

    private static func makeSuggestions(title: String, length: Int, goal: TitleGoal) -> [String] {
        var tips: [String] = []

        if length > 120 {
            tips.append("Shorten to under 80 characters for better mobile visibility.")
        } else if length < 20 {
            tips.append("Add more context — very short titles can feel vague in feeds.")
        }

        if !title.contains("?") && goal == .question {
            tips.append("Reframe as a question to invite comments.")
        }

        if title.range(of: #"\d+"#, options: .regularExpression) == nil && goal == .listicle {
            tips.append("Include a number (e.g. \"5 tips\") for listicle-style engagement.")
        }

        let lower = title.lowercased()
        if goal == .curiosity && !lower.contains("?") {
            tips.append("Add a curiosity hook — hint at a surprising outcome.")
        }

        if tips.isEmpty {
            tips.append("Strong base title — try variants with different hooks below.")
        }

        return tips
    }
}