//
//  HeuristicRanker.swift
//  iris
//
//  Created by Codex.
//

import Foundation

struct UserContext: Equatable {
    var isMoving: Bool
    var city: String

    init(isMoving: Bool, city: String = "London") {
        self.isMoving = isMoving
        self.city = city
    }
}

final class HeuristicRanker {
    private let nowProvider: () -> Int
    private let lastShownAtProvider: (String) -> Int?

    init(now: @escaping () -> Int = { Int(Date().timeIntervalSince1970) },
         lastShownAt: @escaping (String) -> Int? = { _ in nil }) {
        self.nowProvider = now
        self.lastShownAtProvider = lastShownAt
    }

    struct Ranked: Equatable {
        let item: FeedItem
        let confidence: Double
        let isEligibleForRightNow: Bool
    }

    struct WinnerSelection: Equatable {
        let item: FeedItem
        let priority: Double
    }

    func pickWinner(from items: [Ranked], now: Int? = nil, context: UserContext) -> WinnerSelection? {
        let currentTime = now ?? nowProvider()

        let valid = items
            .filter { $0.item.ttlSec > 0 }
            .filter { $0.confidence >= 0.0 }
            .filter { $0.isEligibleForRightNow }

        guard !valid.isEmpty else { return nil }

        var best: (item: FeedItem, score: Double, confidence: Double)?
        for proposed in valid {
            let baseWeight = baseWeight(for: proposed.item.type)
            var score = baseWeight * min(max(proposed.confidence, 0.0), 1.0)
            if let shownAt = lastShownAtProvider(proposed.item.id),
               currentTime - shownAt <= 2 * 60 * 60 {
                score -= 0.4
            }
            if best == nil || score > best!.score {
                best = (proposed.item, score, proposed.confidence)
            }
        }

        guard let best else {
            return nil
        }

        let priority = min(max(best.score, 0.0), 1.0)
        let item = FeedItem(
            id: best.item.id,
            type: best.item.type,
            title: best.item.title.truncated(maxLength: TextConstraints.titleMax),
            subtitle: best.item.subtitle.truncated(maxLength: TextConstraints.subtitleMax),
            priority: priority,
            ttlSec: max(1, best.item.ttlSec),
            condition: best.item.condition,
            startsAt: best.item.startsAt,
            poiType: best.item.poiType,
            bucket: .rightNow,
            actions: ["DISMISS"]
        )
        return WinnerSelection(item: item, priority: priority)
    }

    private func baseWeight(for type: FeedItemType) -> Double {
        switch type {
        case .weatherWarning: return 1.0
        case .weatherAlert: return 0.9
        case .calendarEvent: return 0.8
        case .transit: return 0.75
        case .poiNearby: return 0.6
        case .info: return 0.4
        case .stock: return 0.3
        case .nowPlaying: return 0.25
        case .currentWeather: return 0.0
        case .allQuiet: return 0.0
        }
    }
}