//
//  TravelSegmentIntegrityTests.swift
//  SportsTimeTests
//
//  CRITICAL INVARIANT: Every itinerary option returned to users MUST have
//  valid travel segments between ALL consecutive stops.
//
//  N stops → exactly N-1 travel segments. No exceptions.
//
//  This file tests the invariant at every layer:
//    1. ItineraryBuilder.build() — the segment factory
//    2. ItineraryOption.isValid — the runtime check
//    3. TripPlanningEngine — the final gate
//    4. Each scenario planner (A-E) — end-to-end
//    5. Edge cases — single stops, same-city, missing coords, cross-country
//

import Testing
import Foundation
import CoreLocation
@testable import SportsTime

// MARK: - Layer 1: ItineraryBuilder Invariant

@Suite("Travel Integrity: ItineraryBuilder")
struct TravelIntegrity_BuilderTests {

    @Test("build: 2 stops → exactly 1 segment")
    func build_twoStops_oneSegment() {
        let nyc = TestFixtures.coordinates["New York"]!
        let boston = TestFixtures.coordinates["Boston"]!

        let stops = [
            makeStop(city: "New York", coord: nyc, day: 0),
            makeStop(city: "Boston", coord: boston, day: 1)
        ]

        let result = ItineraryBuilder.build(stops: stops, constraints: .default)
        #expect(result != nil, "NYC→Boston should build")
        #expect(result!.travelSegments.count == 1, "2 stops must have exactly 1 segment")
        #expect(result!.travelSegments[0].estimatedDistanceMiles > 0, "Segment must have distance")
        #expect(result!.travelSegments[0].estimatedDrivingHours > 0, "Segment must have duration")
    }

    @Test("build: 3 stops → exactly 2 segments")
    func build_threeStops_twoSegments() {
        let stops = [
            makeStop(city: "New York", coord: TestFixtures.coordinates["New York"]!, day: 0),
            makeStop(city: "Philadelphia", coord: TestFixtures.coordinates["Philadelphia"]!, day: 1),
            makeStop(city: "Boston", coord: TestFixtures.coordinates["Boston"]!, day: 2)
        ]

        let result = ItineraryBuilder.build(stops: stops, constraints: .default)
        #expect(result != nil)
        #expect(result!.travelSegments.count == 2, "3 stops must have exactly 2 segments")
    }

    @Test("build: 5 stops → exactly 4 segments")
    func build_fiveStops_fourSegments() {
        let cities = ["New York", "Philadelphia", "Boston", "Chicago", "Detroit"]
        let stops = cities.enumerated().map { i, city in
            makeStop(city: city, coord: TestFixtures.coordinates[city]!, day: i)
        }

        let result = ItineraryBuilder.build(stops: stops, constraints: .default)
        #expect(result != nil)
        #expect(result!.travelSegments.count == 4, "5 stops must have exactly 4 segments")
    }

    @Test("build: single stop → 0 segments")
    func build_singleStop_noSegments() {
        let stops = [makeStop(city: "New York", coord: TestFixtures.coordinates["New York"]!, day: 0)]
        let result = ItineraryBuilder.build(stops: stops, constraints: .default)
        #expect(result != nil)
        #expect(result!.travelSegments.isEmpty, "1 stop must have 0 segments")
    }

    @Test("build: empty stops → 0 segments")
    func build_emptyStops_noSegments() {
        let result = ItineraryBuilder.build(stops: [], constraints: .default)
        #expect(result != nil)
        #expect(result!.travelSegments.isEmpty)
        #expect(result!.stops.isEmpty)
    }

    @Test("build: missing coordinates → returns nil (not partial)")
    func build_missingCoords_returnsNil() {
        let stops = [
            makeStop(city: "New York", coord: TestFixtures.coordinates["New York"]!, day: 0),
            makeStop(city: "Atlantis", coord: nil, day: 1),  // No coords!
            makeStop(city: "Boston", coord: TestFixtures.coordinates["Boston"]!, day: 2)
        ]

        let result = ItineraryBuilder.build(stops: stops, constraints: .default)
        #expect(result == nil, "Missing coordinates must reject entire itinerary, not produce partial")
    }

    @Test("build: infeasible segment → returns nil (not partial)")
    func build_infeasibleSegment_returnsNil() {
        // Use extremely tight constraints to make cross-country infeasible
        let tightConstraints = DrivingConstraints(numberOfDrivers: 1, maxHoursPerDriverPerDay: 1.0)

        let stops = [
            makeStop(city: "New York", coord: TestFixtures.coordinates["New York"]!, day: 0),
            makeStop(city: "Los Angeles", coord: TestFixtures.coordinates["Los Angeles"]!, day: 1)
        ]

        // NYC→LA is ~2,800 miles. With 1 hour/day max, exceeds 5x limit (5 hours)
        let result = ItineraryBuilder.build(stops: stops, constraints: tightConstraints)
        #expect(result == nil, "Infeasible segment must reject entire itinerary")
    }

    @Test("build: every segment connects the correct stops in order")
    func build_segmentOrder_matchesStops() {
        let cities = ["New York", "Philadelphia", "Boston"]
        let stops = cities.enumerated().map { i, city in
            makeStop(city: city, coord: TestFixtures.coordinates[city]!, day: i)
        }

        let result = ItineraryBuilder.build(stops: stops, constraints: .default)
        #expect(result != nil)

        // Verify segment endpoints match stop pairs
        for i in 0..<result!.travelSegments.count {
            let segment = result!.travelSegments[i]
            let fromStop = result!.stops[i]
            let toStop = result!.stops[i + 1]

            #expect(segment.fromLocation.name == fromStop.city,
                    "Segment \(i) fromLocation must match stop \(i) city")
            #expect(segment.toLocation.name == toStop.city,
                    "Segment \(i) toLocation must match stop \(i+1) city")
        }
    }

    @Test("build: segment validator rejection → returns nil (not partial)")
    func build_validatorRejection_returnsNil() {
        let stops = [
            makeStop(city: "New York", coord: TestFixtures.coordinates["New York"]!, day: 0),
            makeStop(city: "Boston", coord: TestFixtures.coordinates["Boston"]!, day: 0)  // Same day
        ]

        // Validator always rejects
        let alwaysReject: ItineraryBuilder.SegmentValidator = { _, _, _ in false }

        let result = ItineraryBuilder.build(
            stops: stops, constraints: .default, segmentValidator: alwaysReject
        )
        #expect(result == nil, "Rejected validator must fail entire build")
    }
}

// MARK: - Layer 2: ItineraryOption.isValid

@Suite("Travel Integrity: isValid Property")
struct TravelIntegrity_IsValidTests {

    @Test("isValid: correct segment count → true")
    func isValid_correct_true() {
        let segment = TestFixtures.travelSegment(from: "New York", to: "Boston")
        let option = ItineraryOption(
            rank: 1,
            stops: [
                makeStop(city: "New York", coord: nil, day: 0),
                makeStop(city: "Boston", coord: nil, day: 1)
            ],
            travelSegments: [segment],
            totalDrivingHours: 3.5, totalDistanceMiles: 215,
            geographicRationale: "test"
        )
        #expect(option.isValid == true)
    }

    @Test("isValid: too few segments → false")
    func isValid_tooFew_false() {
        let option = ItineraryOption(
            rank: 1,
            stops: [
                makeStop(city: "New York", coord: nil, day: 0),
                makeStop(city: "Boston", coord: nil, day: 1),
                makeStop(city: "Chicago", coord: nil, day: 2)
            ],
            travelSegments: [TestFixtures.travelSegment(from: "New York", to: "Boston")],
            // Only 1 segment for 3 stops — INVALID
            totalDrivingHours: 3.5, totalDistanceMiles: 215,
            geographicRationale: "test"
        )
        #expect(option.isValid == false, "3 stops with 1 segment must be invalid")
    }

    @Test("isValid: too many segments → false")
    func isValid_tooMany_false() {
        let option = ItineraryOption(
            rank: 1,
            stops: [
                makeStop(city: "New York", coord: nil, day: 0),
                makeStop(city: "Boston", coord: nil, day: 1)
            ],
            travelSegments: [
                TestFixtures.travelSegment(from: "New York", to: "Boston"),
                TestFixtures.travelSegment(from: "Boston", to: "Chicago")
            ],
            // 2 segments for 2 stops — INVALID
            totalDrivingHours: 10, totalDistanceMiles: 800,
            geographicRationale: "test"
        )
        #expect(option.isValid == false, "2 stops with 2 segments must be invalid")
    }

    @Test("isValid: 0 stops with 0 segments → true")
    func isValid_empty_true() {
        let option = ItineraryOption(
            rank: 1, stops: [], travelSegments: [],
            totalDrivingHours: 0, totalDistanceMiles: 0,
            geographicRationale: "empty"
        )
        #expect(option.isValid == true)
    }

    @Test("isValid: 1 stop with 0 segments → true")
    func isValid_singleStop_true() {
        let option = ItineraryOption(
            rank: 1,
            stops: [makeStop(city: "New York", coord: nil, day: 0)],
            travelSegments: [],
            totalDrivingHours: 0, totalDistanceMiles: 0,
            geographicRationale: "single"
        )
        #expect(option.isValid == true)
    }

    @Test("isValid: 1 stop with 1 segment → false (orphan segment)")
    func isValid_singleStopWithSegment_false() {
        let option = ItineraryOption(
            rank: 1,
            stops: [makeStop(city: "New York", coord: nil, day: 0)],
            travelSegments: [TestFixtures.travelSegment(from: "New York", to: "Boston")],
            totalDrivingHours: 3.5, totalDistanceMiles: 215,
            geographicRationale: "orphan segment"
        )
        #expect(option.isValid == false, "1 stop with segments must be invalid")
    }
}

// MARK: - Layer 3: TripPlanningEngine Final Gate

@Suite("Travel Integrity: Engine Final Gate")
struct TravelIntegrity_EngineGateTests {

    @Test("Engine never returns options where isValid is false")
    func engine_neverReturnsInvalid() {
        let baseDate = TestFixtures.date(year: 2026, month: 6, day: 1, hour: 19)

        // Generate realistic games across multiple days
        let cities = ["New York", "Boston", "Philadelphia", "Chicago", "Atlanta"]
        let games = cities.enumerated().map { i, city in
            TestFixtures.game(
                city: city,
                dateTime: TestClock.calendar.date(byAdding: .day, value: i, to: baseDate)!
            )
        }
        let stadiums = TestFixtures.stadiumMap(for: games)

        let prefs = TripPreferences(
            planningMode: .dateRange,
            sports: [.mlb],
            startDate: baseDate,
            endDate: TestClock.calendar.date(byAdding: .day, value: 7, to: baseDate)!
        )

        let request = PlanningRequest(
            preferences: prefs,
            availableGames: games,
            teams: [:],
            stadiums: stadiums
        )

        let engine = TripPlanningEngine()
        let result = engine.planItineraries(request: request)

        guard case .success(let options) = result else { Issue.record("Expected .success, got \(result)"); return }
        for (i, option) in options.enumerated() {
            #expect(option.isValid,
                    "Option \(i) has \(option.stops.count) stops but \(option.travelSegments.count) segments — INVALID")
            // Double-check the math
            if option.stops.count > 1 {
                #expect(option.travelSegments.count == option.stops.count - 1,
                        "Option \(i): \(option.stops.count) stops must have \(option.stops.count - 1) segments, got \(option.travelSegments.count)")
            }
        }
    }

    @Test("Engine rejects all-invalid options with segmentMismatch failure")
    func engine_rejectsAllInvalid() {
        // This tests the isValid filter in applyPreferenceFilters
        // We can't easily inject invalid options, but we verify the code path exists
        let baseDate = TestFixtures.date(year: 2026, month: 6, day: 1, hour: 19)

        let prefs = TripPreferences(
            planningMode: .dateRange,
            sports: [.mlb],
            startDate: baseDate,
            endDate: TestClock.calendar.date(byAdding: .day, value: 1, to: baseDate)!
        )

        // No games → should fail (not return empty success)
        let request = PlanningRequest(preferences: prefs, availableGames: [], teams: [:], stadiums: [:])
        let engine = TripPlanningEngine()
        let result = engine.planItineraries(request: request)

        #expect(!result.isSuccess, "No games should produce failure, not empty success")
    }
}

// MARK: - Layer 4: End-to-End Scenario Tests

@Suite("Travel Integrity: Scenario A (Date Range)")
struct TravelIntegrity_ScenarioATests {

    @Test("ScenarioA: all returned options have N-1 segments")
    func scenarioA_allOptionsValid() {
        let baseDate = TestFixtures.date(year: 2026, month: 6, day: 1, hour: 19)
        let games = ["New York", "Boston", "Philadelphia"].enumerated().map { i, city in
            TestFixtures.game(
                city: city,
                dateTime: TestClock.calendar.date(byAdding: .day, value: i, to: baseDate)!
            )
        }
        let stadiums = TestFixtures.stadiumMap(for: games)

        let prefs = TripPreferences(
            planningMode: .dateRange,
            sports: [.mlb],
            startDate: baseDate,
            endDate: TestClock.calendar.date(byAdding: .day, value: 7, to: baseDate)!
        )

        let request = PlanningRequest(preferences: prefs, availableGames: games, teams: [:], stadiums: stadiums)
        let engine = TripPlanningEngine()
        let result = engine.planItineraries(request: request)

        assertAllOptionsHaveValidTravel(result, scenario: "A")
    }
}

@Suite("Travel Integrity: Scenario B (Selected Games)")
struct TravelIntegrity_ScenarioBTests {

    @Test("ScenarioB: all returned options have N-1 segments")
    func scenarioB_allOptionsValid() {
        let baseDate = TestFixtures.date(year: 2026, month: 6, day: 1, hour: 19)
        let game1 = TestFixtures.game(id: "must_see_1", city: "New York", dateTime: baseDate)
        let game2 = TestFixtures.game(
            id: "must_see_2", city: "Boston",
            dateTime: TestClock.calendar.date(byAdding: .day, value: 2, to: baseDate)!
        )
        let stadiums = TestFixtures.stadiumMap(for: [game1, game2])

        let prefs = TripPreferences(
            planningMode: .gameFirst,
            sports: [.mlb],
            mustSeeGameIds: ["must_see_1", "must_see_2"],
            startDate: baseDate,
            endDate: TestClock.calendar.date(byAdding: .day, value: 7, to: baseDate)!
        )

        let request = PlanningRequest(
            preferences: prefs,
            availableGames: [game1, game2],
            teams: [:],
            stadiums: stadiums
        )

        let engine = TripPlanningEngine()
        let result = engine.planItineraries(request: request)

        assertAllOptionsHaveValidTravel(result, scenario: "B")
    }
}

@Suite("Travel Integrity: Scenario C (Start/End Locations)")
struct TravelIntegrity_ScenarioCTests {

    @Test("ScenarioC: all returned options have N-1 segments including endpoint stops")
    func scenarioC_allOptionsValid() {
        let baseDate = TestFixtures.date(year: 2026, month: 6, day: 1, hour: 19)

        let chicagoCoord = TestFixtures.coordinates["Chicago"]!
        let nycCoord = TestFixtures.coordinates["New York"]!

        // Games along the Chicago → NYC route
        let game1 = TestFixtures.game(
            city: "Detroit",
            dateTime: TestClock.calendar.date(byAdding: .day, value: 1, to: baseDate)!
        )
        let game2 = TestFixtures.game(
            city: "Philadelphia",
            dateTime: TestClock.calendar.date(byAdding: .day, value: 3, to: baseDate)!
        )
        let stadiums = TestFixtures.stadiumMap(for: [game1, game2])

        let prefs = TripPreferences(
            planningMode: .locations,
            startLocation: LocationInput(name: "Chicago", coordinate: chicagoCoord),
            endLocation: LocationInput(name: "New York", coordinate: nycCoord),
            sports: [.mlb],
            startDate: baseDate,
            endDate: TestClock.calendar.date(byAdding: .day, value: 7, to: baseDate)!
        )

        let request = PlanningRequest(
            preferences: prefs,
            availableGames: [game1, game2],
            teams: [:],
            stadiums: stadiums
        )

        let engine = TripPlanningEngine()
        let result = engine.planItineraries(request: request)

        assertAllOptionsHaveValidTravel(result, scenario: "C")
    }
}

@Suite("Travel Integrity: Scenario D (Follow Team)")
struct TravelIntegrity_ScenarioDTests {

    @Test("ScenarioD: all returned options have N-1 segments")
    func scenarioD_allOptionsValid() {
        let baseDate = TestFixtures.date(year: 2026, month: 6, day: 1, hour: 19)
        let teamId = "team_mlb_new_york"

        let game1 = TestFixtures.game(
            city: "New York", dateTime: baseDate,
            homeTeamId: teamId, stadiumId: "stadium_mlb_new_york"
        )
        let game2 = TestFixtures.game(
            city: "Boston",
            dateTime: TestClock.calendar.date(byAdding: .day, value: 3, to: baseDate)!,
            homeTeamId: "team_mlb_boston",
            awayTeamId: teamId,
            stadiumId: "stadium_mlb_boston"
        )
        let stadiums = TestFixtures.stadiumMap(for: [game1, game2])

        let team = TestFixtures.team(id: teamId, name: "Yankees", sport: .mlb, city: "New York")

        let prefs = TripPreferences(
            planningMode: .followTeam,
            sports: [.mlb],
            startDate: baseDate,
            endDate: TestClock.calendar.date(byAdding: .day, value: 7, to: baseDate)!,
            followTeamId: teamId
        )

        let request = PlanningRequest(
            preferences: prefs,
            availableGames: [game1, game2],
            teams: [teamId: team],
            stadiums: stadiums
        )

        let engine = TripPlanningEngine()
        let result = engine.planItineraries(request: request)

        assertAllOptionsHaveValidTravel(result, scenario: "D")
    }
}

@Suite("Travel Integrity: Scenario E (Team-First)")
struct TravelIntegrity_ScenarioETests {

    @Test("ScenarioE: all returned options have N-1 segments")
    func scenarioE_allOptionsValid() {
        let baseDate = TestFixtures.date(year: 2026, month: 6, day: 1, hour: 19)

        let nycTeam = TestFixtures.team(id: "team_nyc", name: "NYC Team", sport: .mlb, city: "New York")
        let bosTeam = TestFixtures.team(id: "team_bos", name: "BOS Team", sport: .mlb, city: "Boston")

        // Create home games for each team
        let nycGames = (0..<3).map { i in
            TestFixtures.game(
                id: "nyc_\(i)", city: "New York",
                dateTime: TestClock.calendar.date(byAdding: .day, value: i * 2, to: baseDate)!,
                homeTeamId: "team_nyc", stadiumId: "stadium_mlb_new_york"
            )
        }
        let bosGames = (0..<3).map { i in
            TestFixtures.game(
                id: "bos_\(i)", city: "Boston",
                dateTime: TestClock.calendar.date(byAdding: .day, value: i * 2 + 1, to: baseDate)!,
                homeTeamId: "team_bos", stadiumId: "stadium_mlb_boston"
            )
        }

        let allGames = nycGames + bosGames
        let stadiums = TestFixtures.stadiumMap(for: allGames)
        let teams: [String: Team] = ["team_nyc": nycTeam, "team_bos": bosTeam]

        let prefs = TripPreferences(
            planningMode: .teamFirst,
            sports: [.mlb],
            selectedTeamIds: ["team_nyc", "team_bos"]
        )

        let request = PlanningRequest(
            preferences: prefs,
            availableGames: allGames,
            teams: teams,
            stadiums: stadiums
        )

        let engine = TripPlanningEngine()
        let result = engine.planItineraries(request: request)

        assertAllOptionsHaveValidTravel(result, scenario: "E")
    }
}

// MARK: - Layer 5: Edge Cases

@Suite("Travel Integrity: Edge Cases")
struct TravelIntegrity_EdgeCaseTests {

    @Test("Same-city consecutive stops have zero-distance segment")
    func sameCityStops_haveZeroDistanceSegment() {
        let coord = TestFixtures.coordinates["New York"]!
        let stops = [
            makeStop(city: "New York", coord: coord, day: 0),
            makeStop(city: "New York", coord: coord, day: 1)
        ]

        let result = ItineraryBuilder.build(stops: stops, constraints: .default)
        #expect(result != nil, "Same-city stops should build")
        #expect(result!.travelSegments.count == 1, "Must still have segment")
        // Distance should be very small (same coords)
    }

    @Test("Cross-country trip (NYC→LA) rejected with 1 driver, feasible with 2")
    func crossCountry_feasibilityDependsOnDrivers() {
        let stops = [
            makeStop(city: "New York", coord: TestFixtures.coordinates["New York"]!, day: 0),
            makeStop(city: "Los Angeles", coord: TestFixtures.coordinates["Los Angeles"]!, day: 5)
        ]

        // 1 driver, 8 hrs/day → max 40 hrs (5x limit). NYC→LA is ~53 hrs → infeasible
        let oneDriver = ItineraryBuilder.build(stops: stops, constraints: .default)
        #expect(oneDriver == nil, "NYC→LA exceeds 5x daily limit for 1 driver")

        // 2 drivers, 8 hrs each → 16 hrs/day → max 80 hrs → feasible
        let twoDriverConstraints = DrivingConstraints(numberOfDrivers: 2, maxHoursPerDriverPerDay: 8.0)
        let twoDrivers = ItineraryBuilder.build(stops: stops, constraints: twoDriverConstraints)
        #expect(twoDrivers != nil, "NYC→LA should build with 2 drivers")
        if let built = twoDrivers {
            #expect(built.travelSegments.count == 1)
            #expect(built.travelSegments[0].estimatedDistanceMiles > 2000,
                    "NYC→LA should be 2000+ miles")
        }
    }

    @Test("Multi-stop trip never has mismatched segment count")
    func multiStopTrip_neverMismatched() {
        // Property test: for any number of stops 2-10, segments == stops - 1
        let allCities = ["New York", "Boston", "Philadelphia", "Chicago", "Detroit",
                         "Atlanta", "Miami", "Houston", "Denver", "Minneapolis"]

        for stopCount in 2...min(10, allCities.count) {
            let cities = Array(allCities.prefix(stopCount))
            let stops = cities.enumerated().map { i, city in
                makeStop(city: city, coord: TestFixtures.coordinates[city]!, day: i)
            }

            let result = ItineraryBuilder.build(stops: stops, constraints: .default)
            if let built = result {
                #expect(built.travelSegments.count == stopCount - 1,
                        "\(stopCount) stops must produce \(stopCount - 1) segments, got \(built.travelSegments.count)")
            }
            // nil is acceptable (infeasible), but never partial
        }
    }

    @Test("Every travel segment has positive distance when cities differ")
    func everySegment_hasPositiveDistance() {
        let cities = ["New York", "Boston", "Philadelphia", "Chicago"]
        let stops = cities.enumerated().map { i, city in
            makeStop(city: city, coord: TestFixtures.coordinates[city]!, day: i)
        }

        let result = ItineraryBuilder.build(stops: stops, constraints: .default)
        #expect(result != nil)

        for (i, segment) in result!.travelSegments.enumerated() {
            #expect(segment.estimatedDistanceMiles > 0,
                    "Segment \(i) (\(segment.fromLocation.name)→\(segment.toLocation.name)) must have positive distance")
            #expect(segment.estimatedDrivingHours > 0,
                    "Segment \(i) must have positive driving hours")
        }
    }

    @Test("Segment from/to locations match adjacent stops")
    func segmentEndpoints_matchAdjacentStops() {
        let baseDate = TestFixtures.date(year: 2026, month: 6, day: 1, hour: 19)
        let cities = ["New York", "Boston", "Philadelphia"]
        let games = cities.enumerated().map { i, city in
            TestFixtures.game(
                city: city,
                dateTime: TestClock.calendar.date(byAdding: .day, value: i, to: baseDate)!
            )
        }
        let stadiums = TestFixtures.stadiumMap(for: games)

        let prefs = TripPreferences(
            planningMode: .dateRange,
            sports: [.mlb],
            startDate: baseDate,
            endDate: TestClock.calendar.date(byAdding: .day, value: 7, to: baseDate)!
        )

        let request = PlanningRequest(
            preferences: prefs, availableGames: games, teams: [:], stadiums: stadiums
        )

        let engine = TripPlanningEngine()
        let result = engine.planItineraries(request: request)

        guard case .success(let options) = result else { Issue.record("Expected .success, got \(result)"); return }
        for option in options {
            for i in 0..<option.travelSegments.count {
                let segment = option.travelSegments[i]
                let fromStop = option.stops[i]
                let toStop = option.stops[i + 1]

                // Segment endpoints should match stop cities
                #expect(segment.fromLocation.name == fromStop.city,
                        "Segment \(i) from '\(segment.fromLocation.name)' should match stop '\(fromStop.city)'")
                #expect(segment.toLocation.name == toStop.city,
                        "Segment \(i) to '\(segment.toLocation.name)' should match stop '\(toStop.city)'")
            }
        }
    }
}

// MARK: - Stress Tests

@Suite("Travel Integrity: Stress Tests")
struct TravelIntegrity_StressTests {

    @Test("Large game set: all options still have valid travel")
    func largeGameSet_allOptionsValid() {
        let baseDate = TestFixtures.date(year: 2026, month: 6, day: 1, hour: 19)

        // 15 games across 5 cities over 2 weeks
        let cities = ["New York", "Boston", "Philadelphia", "Chicago", "Atlanta"]
        var games: [Game] = []
        for i in 0..<15 {
            let city = cities[i % cities.count]
            let date = TestClock.calendar.date(byAdding: .day, value: i, to: baseDate)!
            games.append(TestFixtures.game(city: city, dateTime: date))
        }
        let stadiums = TestFixtures.stadiumMap(for: games)

        let prefs = TripPreferences(
            planningMode: .dateRange,
            sports: [.mlb],
            startDate: baseDate,
            endDate: TestClock.calendar.date(byAdding: .day, value: 15, to: baseDate)!
        )

        let request = PlanningRequest(
            preferences: prefs, availableGames: games, teams: [:], stadiums: stadiums
        )

        let engine = TripPlanningEngine()
        let result = engine.planItineraries(request: request)

        assertAllOptionsHaveValidTravel(result, scenario: "A-large")
    }

    @Test("All scenarios with allowRepeatCities=false still have valid travel")
    func noRepeatCities_stillValidTravel() {
        let baseDate = TestFixtures.date(year: 2026, month: 6, day: 1, hour: 19)

        let games = ["New York", "Boston", "Philadelphia", "Chicago"].enumerated().map { i, city in
            TestFixtures.game(
                city: city,
                dateTime: TestClock.calendar.date(byAdding: .day, value: i, to: baseDate)!
            )
        }
        let stadiums = TestFixtures.stadiumMap(for: games)

        let prefs = TripPreferences(
            planningMode: .dateRange,
            sports: [.mlb],
            startDate: baseDate,
            endDate: TestClock.calendar.date(byAdding: .day, value: 7, to: baseDate)!,
            allowRepeatCities: false
        )

        let request = PlanningRequest(
            preferences: prefs, availableGames: games, teams: [:], stadiums: stadiums
        )

        let engine = TripPlanningEngine()
        let result = engine.planItineraries(request: request)

        assertAllOptionsHaveValidTravel(result, scenario: "A-noRepeat")
    }

    @Test("Scenario with must-stop constraint still has valid travel")
    func mustStop_stillValidTravel() {
        let baseDate = TestFixtures.date(year: 2026, month: 6, day: 1, hour: 19)

        let games = ["New York", "Boston", "Philadelphia"].enumerated().map { i, city in
            TestFixtures.game(
                city: city,
                dateTime: TestClock.calendar.date(byAdding: .day, value: i, to: baseDate)!
            )
        }
        let stadiums = TestFixtures.stadiumMap(for: games)

        let prefs = TripPreferences(
            planningMode: .dateRange,
            sports: [.mlb],
            startDate: baseDate,
            endDate: TestClock.calendar.date(byAdding: .day, value: 7, to: baseDate)!,
            mustStopLocations: [LocationInput(name: "Boston")]
        )

        let request = PlanningRequest(
            preferences: prefs, availableGames: games, teams: [:], stadiums: stadiums
        )

        let engine = TripPlanningEngine()
        let result = engine.planItineraries(request: request)

        assertAllOptionsHaveValidTravel(result, scenario: "A-mustStop")
    }
}

// MARK: - Test Helpers

/// Asserts that ALL options in a result have valid travel segments.
/// This is THE critical assertion for this test file.
private func assertAllOptionsHaveValidTravel(
    _ result: ItineraryResult,
    scenario: String,
    sourceLocation: SourceLocation = #_sourceLocation
) {
    guard case .success(let options) = result else {
        // Failure is OK — means engine couldn't find valid routes
        // What's NOT OK is returning invalid success
        return
    }

    #expect(!options.isEmpty, "Scenario \(scenario): success should have options",
            sourceLocation: sourceLocation)

    for (i, option) in options.enumerated() {
        // THE CRITICAL CHECK
        #expect(option.isValid,
                "Scenario \(scenario) option \(i): \(option.stops.count) stops must have \(max(0, option.stops.count - 1)) segments, got \(option.travelSegments.count)",
                sourceLocation: sourceLocation)

        // Additional checks
        if option.stops.count > 1 {
            #expect(option.travelSegments.count == option.stops.count - 1,
                    "Scenario \(scenario) option \(i): segment count mismatch",
                    sourceLocation: sourceLocation)

            // Every segment must have non-negative distance
            for (j, seg) in option.travelSegments.enumerated() {
                #expect(seg.estimatedDistanceMiles >= 0,
                        "Scenario \(scenario) option \(i) segment \(j): negative distance",
                        sourceLocation: sourceLocation)
            }
        }
    }
}

/// Helper to create a basic ItineraryStop for testing.
private func makeStop(
    city: String,
    coord: CLLocationCoordinate2D?,
    day: Int
) -> ItineraryStop {
    let date = TestClock.addingDays(day)
    return ItineraryStop(
        city: city,
        state: TestFixtures.states[city] ?? "",
        coordinate: coord,
        games: ["game_\(city.lowercased())_\(day)"],
        arrivalDate: date,
        departureDate: date,
        location: LocationInput(name: city, coordinate: coord),
        firstGameStart: date
    )
}