import Foundation
import Testing
import IndieSync
@testable import Workouts

/// Locks the decision table of `SeedReconcilePlanner` — the safety-critical logic that
/// upgrades stale starter-seed revisions and adds newly-shipped seeds on an existing
/// install without ever duplicating a user's split, resurrecting a deleted seed, or
/// downgrade-rewriting a newer app version's file. All fixtures are plain structs so
/// every assertion is a pure, deterministic function of the inputs.
struct SeedReconcilePlannerTests {

    // MARK: - Fixtures

    private func exercise(
        name: String, order: Int = 0, sets: Int = 3, reps: Int = 10, weight: Double = 100
    ) -> ExerciseDocument {
        ExerciseDocument(
            id: "EX-\(name)-\(order)", name: name, order: order, sets: sets, reps: reps,
            weight: weight, loadType: LoadType.weight.rawValue, durationSeconds: 0
        )
    }

    /// A seed-shaped split at the current schema version, with a fixed frozen date so
    /// two builds of "the same" content compare equal.
    private func seed(
        id: String = "01DXF6DT0038BDC2WC3EVX8ZJ5",
        name: String = "Upper Body",
        schemaVersion: Int = SplitDocument.currentSchemaVersion,
        exercises: [ExerciseDocument]? = nil
    ) -> SplitDocument {
        SplitDocument(
            schemaVersion: schemaVersion, id: id, name: name, color: "indigo",
            systemImage: "dumbbell.fill", order: 0,
            createdAt: Date(timeIntervalSince1970: 0), updatedAt: Date(timeIntervalSince1970: 0),
            exercises: exercises ?? [exercise(name: "Bench Press")], activityType: nil
        )
    }

    // MARK: - Live file present

    /// An older app version wrote this seed at schemaVersion 1 (and, on disk, carried
    /// extra now-removed keys — which decode into the current struct as simply absent).
    /// The content is otherwise identical, so normalizing the version stamp must make it
    /// read as up to date: no churn, no rewrite.
    @Test func semanticEqualitySkipsAcrossSchemaVersions() {
        let bundle = seed()                 // current schemaVersion
        var live = bundle
        live.schemaVersion = 1              // older wrapper, same content
        let input = SeedReconcileInput(seedID: bundle.id, seedDoc: bundle, liveDoc: live, hasStub: false)

        #expect(SeedReconcilePlanner.decision(for: input, liveSplitNames: []) == .skip(.upToDate))
    }

    /// The bundle seed gained an exercise since this install wrote its file — a real
    /// content change must upgrade (overwrite with current bundle bytes), even though
    /// the live file is a lower schema version.
    @Test func contentChangeUpgrades() {
        let bundle = seed(exercises: [exercise(name: "Bench Press"), exercise(name: "Overhead Press", order: 1)])
        var live = seed(exercises: [exercise(name: "Bench Press")])   // one fewer exercise
        live.schemaVersion = 1
        let input = SeedReconcileInput(seedID: bundle.id, seedDoc: bundle, liveDoc: live, hasStub: false)

        #expect(SeedReconcilePlanner.decision(for: input, liveSplitNames: []) == .upgrade)
    }

    /// A weight tweak alone is enough of a content change to upgrade.
    @Test func exerciseWeightChangeUpgrades() {
        let bundle = seed(exercises: [exercise(name: "Bench Press", weight: 135)])
        let live = seed(exercises: [exercise(name: "Bench Press", weight: 115)])
        let input = SeedReconcileInput(seedID: bundle.id, seedDoc: bundle, liveDoc: live, hasStub: false)

        #expect(SeedReconcilePlanner.decision(for: input, liveSplitNames: []) == .upgrade)
    }

    /// A live file written by a NEWER app version (schemaVersion above current) is
    /// quarantined — never downgrade-rewrite it, even though it differs.
    @Test func newerSchemaFileIsQuarantined() {
        let bundle = seed()
        var live = seed(exercises: [exercise(name: "Something New")])
        live.schemaVersion = SplitDocument.currentSchemaVersion + 1
        #expect(!live.isReadable)   // guards the premise
        let input = SeedReconcileInput(seedID: bundle.id, seedDoc: bundle, liveDoc: live, hasStub: false)

        #expect(SeedReconcilePlanner.decision(for: input, liveSplitNames: []) == .skip(.quarantined))
    }

    // MARK: - No live file

    /// No live file but a stub exists → the user deleted this seed. The veto stands.
    @Test func stubVetoesResurrection() {
        let bundle = seed()
        let input = SeedReconcileInput(seedID: bundle.id, seedDoc: bundle, liveDoc: nil, hasStub: true)

        #expect(SeedReconcilePlanner.decision(for: input, liveSplitNames: []) == .skip(.vetoed))
    }

    /// No live file, no stub, but a live split (a legacy runtime-built or user-cloned
    /// "Upper Body") already uses the seed's name → writing it would duplicate by name.
    @Test func nameCollisionSkips() {
        let bundle = seed(name: "Upper Body")
        let input = SeedReconcileInput(seedID: bundle.id, seedDoc: bundle, liveDoc: nil, hasStub: false)

        #expect(SeedReconcilePlanner.decision(for: input, liveSplitNames: ["Upper Body", "Core"]) == .skip(.nameCollision))
    }

    /// No live file, no stub, no same-name split → a genuinely missing seed (newly
    /// shipped, or a pre-fixed-ULID install) gets written.
    @Test func missingSeedIsWritten() {
        let bundle = seed(name: "Bodyweight Core")
        let input = SeedReconcileInput(seedID: bundle.id, seedDoc: bundle, liveDoc: nil, hasStub: false)

        #expect(SeedReconcilePlanner.decision(for: input, liveSplitNames: ["Upper Body", "Core"]) == .write)
    }

    /// A stub present but the same name also live: the veto is checked first, so it
    /// still skips (as vetoed) rather than as a name collision — either way, no write.
    @Test func stubTakesPrecedenceOverNameCollision() {
        let bundle = seed(name: "Upper Body")
        let input = SeedReconcileInput(seedID: bundle.id, seedDoc: bundle, liveDoc: nil, hasStub: true)

        #expect(SeedReconcilePlanner.decision(for: input, liveSplitNames: ["Upper Body"]) == .skip(.vetoed))
    }

    // MARK: - Restore

    /// Restore rewrites only a seed that is both absent and free of a name collision;
    /// the presence of a veto stub is irrelevant (restore lifts it).
    @Test func shouldRestoreOnlyWhenAbsentAndNameFree() {
        // Absent, name free → restore (whether or not a stub exists).
        #expect(SeedReconcilePlanner.shouldRestore(hasLiveFile: false, seedName: "Upper Body", liveSplitNames: []))
        // Live file already present → reconcile handles any upgrade; restore leaves it.
        #expect(!SeedReconcilePlanner.shouldRestore(hasLiveFile: true, seedName: "Upper Body", liveSplitNames: []))
        // A live same-name split exists → don't duplicate it.
        #expect(!SeedReconcilePlanner.shouldRestore(hasLiveFile: false, seedName: "Upper Body", liveSplitNames: ["Upper Body"]))
    }
}