//
//  FoundationModelsReflectionService.swift
//  Reflect
//
//  Generates personalized AI feedback after a user completes a guided reflection.
//

import Foundation
import FoundationModels

@available(iOS 26, *)
@MainActor
class FoundationModelsReflectionService {

    // MARK: - Initialization

    init() {}

    // MARK: - Feedback Generation

    /// Generate personalized feedback based on a completed guided reflection
    /// - Parameters:
    ///   - reflection: The completed guided reflection with Q&A responses
    ///   - mood: The mood associated with this entry
    /// - Returns: AI-generated reflection feedback
    func generateFeedback(
        for reflection: GuidedReflection,
        mood: Mood
    ) async throws -> AIReflectionFeedback {
        let session = LanguageModelSession(instructions: systemInstructions)
        let prompt = buildPrompt(from: reflection, mood: mood)
        let response = try await session.respond(
            to: prompt,
            generating: AIReflectionFeedback.self,
            options: GenerationOptions(maximumResponseTokens: 200)
        )
        return response.content
    }

    // MARK: - System Instructions

    private var systemInstructions: String {
        let personalityPack = UserDefaultsStore.personalityPackable()

        switch personalityPack {
        case .Default:
            return defaultInstructions
        case .MotivationalCoach:
            return coachInstructions
        case .ZenMaster:
            return zenInstructions
        case .BestFriend:
            return bestFriendInstructions
        case .DataAnalyst:
            return analystInstructions
        }
    }

    private var defaultInstructions: String {
        """
        You are a warm, supportive companion responding to someone who just completed a guided mood reflection. \
        Validate their effort, reflect their own words back to them, and offer a gentle takeaway. \
        Be specific — reference what they actually wrote. Keep each field to 1 sentence. \
        SF Symbols: sparkles, heart.fill, star.fill, sun.max.fill, leaf.fill
        """
    }

    private var coachInstructions: String {
        """
        You are a HIGH ENERGY motivational coach responding to someone who just completed a guided mood reflection! \
        Celebrate their self-awareness, pump them up about the growth they showed, and give them a power move for tomorrow. \
        Reference what they actually wrote. Keep each field to 1 sentence. Use exclamations! \
        SF Symbols: trophy.fill, flame.fill, bolt.fill, star.fill, figure.run
        """
    }

    private var zenInstructions: String {
        """
        You are a calm, mindful guide responding to someone who just completed a guided mood reflection. \
        Acknowledge their practice of self-awareness with gentle wisdom. Use nature metaphors. \
        Reference what they actually wrote. Keep each field to 1 sentence. Speak with serene clarity. \
        SF Symbols: leaf.fill, moon.fill, drop.fill, sunrise.fill, wind
        """
    }

    private var bestFriendInstructions: String {
        """
        You are their supportive best friend responding after they completed a guided mood reflection. \
        Be warm, casual, and validating. Use conversational tone. \
        Reference what they actually wrote. Keep each field to 1 sentence. \
        SF Symbols: heart.fill, hand.thumbsup.fill, sparkles, star.fill, face.smiling.fill
        """
    }

    private var analystInstructions: String {
        """
        You are a clinical data analyst providing feedback on a completed mood reflection. \
        Note the cognitive patterns observed, the technique application quality, and a data-informed recommendation. \
        Reference what they actually wrote. Keep each field to 1 sentence. Be objective but encouraging. \
        SF Symbols: chart.bar.fill, brain.head.profile, doc.text.magnifyingglass, chart.line.uptrend.xyaxis
        """
    }

    // MARK: - Prompt Construction

    private func buildPrompt(from reflection: GuidedReflection, mood: Mood) -> String {
        let moodName = mood.widgetDisplayName
        let technique = reflection.moodCategory.techniqueName

        let qaPairs = reflection.responses
            .filter { !$0.answer.trimmingCharacters(in: .whitespacesAndNewlines).isEmpty }
            .map { response in
                let chips = response.selectedChips.isEmpty ? "" : " [themes: \(response.selectedChips.joined(separator: ", "))]"
                return "Q: \(response.question)\nA: \(response.answer)\(chips)"
            }
            .joined(separator: "\n\n")

        // Intensity shift — if captured, tells the AI how much the reflection helped.
        var intensityLine = ""
        if let pre = reflection.preIntensity, let post = reflection.postIntensity {
            let delta = post - pre
            let direction: String
            if delta < 0 {
                direction = "dropped by \(abs(delta))"
            } else if delta > 0 {
                direction = "rose by \(delta)"
            } else {
                direction = "stayed the same"
            }
            intensityLine = "\nEmotional intensity: \(pre)/10 before → \(post)/10 after (\(direction)).\n"
        } else if let pre = reflection.preIntensity {
            intensityLine = "\nStarting emotional intensity: \(pre)/10.\n"
        }

        // Detected cognitive distortion — if present, helps the AI speak to the specific
        // pattern the user worked through (e.g., "you caught yourself overgeneralizing").
        var distortionLine = ""
        if let distortion = reflection.detectedDistortion, distortion != .unknown {
            distortionLine = "\nDetected cognitive distortion in their automatic thought: \(distortion.rawValue). " +
                "Reference this pattern naturally in your observation without being clinical.\n"
        }

        return """
        The user logged their mood as "\(moodName)" and completed a \(technique) reflection:
        \(intensityLine)\(distortionLine)
        \(qaPairs)

        Respond with personalized feedback that references their specific answers\
        \(reflection.preIntensity != nil && reflection.postIntensity != nil ? " and acknowledges the shift in how they're feeling" : "").
        """
    }
}