//
//  POIDataSource.swift
//  iris
//
//  Created by Codex.
//

import CoreLocation
import Foundation
import MapKit

struct POIDataSourceConfig: Sendable {
    var maxCandidates: Int = 2
    var searchRadiusMeters: CLLocationDistance = 600
    var transitBoostRadiusMeters: CLLocationDistance = 200
    var walkingSpeedMps: Double = 1.4
    var minTTLSeconds: Int = 60
    var maxTTLSeconds: Int = 20 * 60
    init() {}
}

/// MapKit-backed POI source.
final class POIDataSource {
    enum POIType: String, Codable, CaseIterable, Sendable {
        case transit = "TRANSIT"
        case cafe = "CAFE"
        case food = "FOOD"
        case park = "PARK"
        case shopping = "SHOPPING"
        case grocery = "GROCERY"
        case fitness = "FITNESS"
        case entertainment = "ENTERTAINMENT"
        case health = "HEALTH"
        case lodging = "LODGING"
        case education = "EDUCATION"
        case services = "SERVICES"
        case other = "OTHER"
    }

    struct POI: Sendable, Equatable {
        let id: String
        let name: String
        let category: String
        let poiType: POIType
        let distanceMeters: CLLocationDistance
        let walkingMinutes: Int
        let ttlSec: Int
        let confidence: Double
        let isTransit: Bool
    }

    private let config: POIDataSourceConfig

    init(config: POIDataSourceConfig = .init()) {
        self.config = config
    }

    func data(for location: CLLocation, now: Int) async throws -> [POI] {
        print("finding pois for location \(location)")
        
        _ = now

        let request = MKLocalPointsOfInterestRequest(
            center: location.coordinate,
            radius: config.searchRadiusMeters
        )
        request.pointOfInterestFilter = .includingAll

        let items = try await search(request: request)
        
        print(items)

        var results: [POI] = []
        results.reserveCapacity(min(items.count, config.maxCandidates))
        var seen: Set<String> = []

        for item in items {
            let name = (item.name ?? "").trimmingCharacters(in: .whitespacesAndNewlines)
            guard !name.isEmpty else { continue }

            let coordinate = item.placemark.coordinate
            let itemLocation = item.placemark.location ?? CLLocation(latitude: coordinate.latitude, longitude: coordinate.longitude)
            let distance = location.distance(from: itemLocation)
            guard distance <= config.searchRadiusMeters else { continue }

            let mkCategory = item.pointOfInterestCategory
            let categoryRaw = mkCategory?.rawValue
            let category = categoryLabel(from: categoryRaw)
            let poiType = poiType(for: mkCategory, categoryRaw: categoryRaw, name: name)
            let isTransit = poiType == .transit
            let walkingMinutes = walkingMinutes(for: distance)
            let ttlSec = ttlSeconds(radius: config.searchRadiusMeters, speed: location.speed)
            let confidence = confidenceScore(distance: distance, isTransit: isTransit)

            let id = stableId(name: name, coordinate: coordinate, category: poiType.rawValue)
            guard !seen.contains(id) else { continue }
            seen.insert(id)

            results.append(
                POI(
                    id: id,
                    name: name,
                    category: category,
                    poiType: poiType,
                    distanceMeters: distance,
                    walkingMinutes: walkingMinutes,
                    ttlSec: ttlSec,
                    confidence: confidence,
                    isTransit: isTransit
                )
            )
        }

        results.sort {
            if $0.confidence == $1.confidence {
                return $0.distanceMeters < $1.distanceMeters
            }
            return $0.confidence > $1.confidence
        }

        if results.count > config.maxCandidates {
            return Array(results.prefix(config.maxCandidates))
        }
        return results
    }

    private func search(request: MKLocalPointsOfInterestRequest) async throws -> [MKMapItem] {
        try await withCheckedThrowingContinuation { continuation in
            let search = MKLocalSearch(request: request)
            search.start { response, error in
                if let error {
                    continuation.resume(throwing: error)
                    return
                }
                continuation.resume(returning: response?.mapItems ?? [])
            }
        }
    }

    private func stableId(name: String, coordinate: CLLocationCoordinate2D, category: String) -> String {
        let lat = String(format: "%.5f", coordinate.latitude)
        let lon = String(format: "%.5f", coordinate.longitude)
        let rawCategory = category.lowercased()
        let raw = "poi:\(rawCategory):\(name):\(lat):\(lon)"
        return raw
            .replacingOccurrences(of: " ", with: "_")
            .replacingOccurrences(of: "\n", with: "_")
            .replacingOccurrences(of: "\t", with: "_")
    }

    private func walkingMinutes(for distanceMeters: CLLocationDistance) -> Int {
        let speed = max(config.walkingSpeedMps, 0.5)
        let seconds = distanceMeters / speed
        let minutes = Int(ceil(seconds / 60.0))
        return max(1, minutes)
    }

    private func ttlSeconds(radius: CLLocationDistance, speed: CLLocationSpeed) -> Int {
        let safeSpeed = max(speed, 0.5)
        let secondsToExit = radius / safeSpeed
        let ttl = Int(secondsToExit.rounded())
        return min(max(ttl, config.minTTLSeconds), config.maxTTLSeconds)
    }

    private func confidenceScore(distance: CLLocationDistance, isTransit: Bool) -> Double {
        let normalized = max(0.0, min(1.0, 1.0 - (distance / max(config.searchRadiusMeters, 1))))
        let base = isTransit ? 0.55 : 0.25
        let range = isTransit ? 0.25 : 0.2
        let transitBoost = (isTransit && distance <= config.transitBoostRadiusMeters) ? 0.1 : 0.0
        return min(max(base + (range * normalized) + transitBoost, 0.0), 0.9)
    }

    private func categoryLabel(from raw: String?) -> String {
        guard var raw = raw else { return "Place" }
        if raw.hasPrefix("MKPOICategory") {
            raw = String(raw.dropFirst("MKPOICategory".count))
        }
        raw = raw.replacingOccurrences(of: "_", with: " ").replacingOccurrences(of: "-", with: " ")
        if raw.isEmpty { return "Place" }

        var result = ""
        for scalar in raw.unicodeScalars {
            if CharacterSet.uppercaseLetters.contains(scalar),
               let last = result.unicodeScalars.last,
               !CharacterSet.whitespaces.contains(last) {
                result.append(" ")
            }
            result.append(String(scalar))
        }
        let trimmed = result.trimmingCharacters(in: .whitespacesAndNewlines)
        return trimmed.isEmpty ? "Place" : trimmed
    }

    private func isTransitCategory(categoryRaw: String?, name: String) -> Bool {
        let haystack = ([categoryRaw, name].compactMap { $0 }.joined(separator: " ")).lowercased()
        let tokens = ["bus", "train", "rail", "subway", "metro", "tram", "ferry", "transit", "transport"]
        return tokens.contains { haystack.contains($0) }
    }

    private func poiType(for category: MKPointOfInterestCategory?, categoryRaw: String?, name: String) -> POIType {
        if let category {
            switch category {
            case .publicTransport, .airport:
                return .transit
            case .cafe:
                return .cafe
            case .restaurant, .bakery, .brewery, .winery:
                return .food
            case .foodMarket:
                return .grocery
            case .park, .nationalPark, .beach, .campground, .marina:
                return .park
            case .fitnessCenter:
                return .fitness
            case .hotel:
                return .lodging
            case .school, .university, .library:
                return .education
            case .hospital, .pharmacy:
                return .health
            case .store:
                return .shopping
            case .movieTheater, .museum, .nightlife, .amusementPark, .aquarium, .stadium, .theater, .zoo:
                return .entertainment
            case .atm, .bank, .postOffice, .police, .fireStation, .parking, .laundry, .carRental, .evCharger, .restroom:
                return .services
            default:
                break
            }
        }

        if isTransitCategory(categoryRaw: categoryRaw, name: name) {
            return .transit
        }

        let lower = name.lowercased()
        if lower.contains("cafe") || lower.contains("coffee") {
            return .cafe
        }
        if lower.contains("restaurant") || lower.contains("pizza") || lower.contains("food") {
            return .food
        }
        if lower.contains("market") || lower.contains("grocery") {
            return .grocery
        }
        if lower.contains("park") {
            return .park
        }
        if lower.contains("gym") || lower.contains("fitness") {
            return .fitness
        }
        if lower.contains("museum") || lower.contains("theater") || lower.contains("cinema") || lower.contains("zoo") {
            return .entertainment
        }
        if lower.contains("school") || lower.contains("university") || lower.contains("college") {
            return .education
        }
        if lower.contains("hotel") {
            return .lodging
        }
        if lower.contains("hospital") || lower.contains("pharmacy") {
            return .health
        }
        if lower.contains("mall") || lower.contains("store") || lower.contains("shop") {
            return .shopping
        }

        return .other
    }

}