import Foundation
import Hummingbird
import HummingbirdElementary
import Infrastructure
import Persistence

/// Serves what a collector uses: the want list, for a signed-in account, and the public series screens and comparison.
///
/// - Note: `Context` is the request context the routes are resolved against, and must match the context of the router the routes are added to.
public struct CollectingController<Context: RequestContext> {

    // MARK: Properties

    private let analytics: Analytics?
    private let assetVersion: String?

    /// The repository listings are read through.
    private let catalogue: CatalogueRepository

    /// The repository wants and series are read and written through.
    private let collecting: CollectingRepository

    /// The store the signed-in account is read from.
    private let sessions: SessionStore

    // MARK: Initializers

    /// Creates a collecting controller.
    /// - Parameters:
    ///   - collecting: the repository wants and series are read and written through.
    ///   - catalogue: the repository listings are read through.
    ///   - sessions: the store the signed-in account is read from.
    ///   - assetVersion: the version token appended to the pages' asset URLs, or `nil` (the default) to leave them unversioned.
    ///   - analytics: the analytics tracker the pages embed, or `nil` (the default) to omit it.
    public init(
        collecting: CollectingRepository,
        catalogue: CatalogueRepository,
        sessions: SessionStore,
        assetVersion: String? = nil,
        analytics: Analytics? = nil
    ) {
        self.analytics = analytics
        self.assetVersion = assetVersion
        self.catalogue = catalogue
        self.collecting = collecting
        self.sessions = sessions
    }

}

// MARK: - RouterController

extension CollectingController: RouterController {

    // MARK: Properties

    public var routes: RouteCollection<Context> {
        let routes = RouteCollection(context: Context.self)

        routes.get(.init(.Route.wants), use: wants)
        routes.post(.init(.Route.wants), use: addWant)
        routes.get(.init("\(String.Route.wants)/new"), use: newWant)
        routes.post(.init("\(String.Route.wants)/:id/alerts"), use: toggleAlerts)
        routes.post(.init("\(String.Route.wants)/:id/remove"), use: removeWant)
        routes.get(.init(.Route.series), use: seriesIndex)
        routes.get(.init("\(String.Route.series)/:slug"), use: series)
        routes.get(.init(.Route.compare), use: compare)

        return routes
    }

}

// MARK: - Wants

private extension CollectingController {

    /// Handles a want posted from the form.
    @Sendable
    func addWant(
        request: Request,
        context: Context
    ) async throws -> Response {
        guard let user = await sessions.user(for: request) else {
            return .redirect(to: .Route.signIn(returningTo: .Route.wants), type: .normal)
        }

        let form = try await URLEncodedFormDecoder().decode(WantForm.self, from: request, context: context)

        try await collecting.addWant(
            title: form.title,
            minGrade: form.minGrade.flatMap(Double.init),
            maxPriceCents: form.maxPrice.flatMap { Int($0.trimmingCharacters(in: .whitespaces)) }.flatMap { $0 > 0 ? $0 * 100 : nil },
            slabbedOnly: form.slabbed == "1",
            for: user
        )

        return .redirect(to: .Route.wants, type: .normal)
    }

    /// Handles a request for the add-a-want form, filled from a listing being saved, or with a title — a gap in a series.
    @Sendable
    func newWant(
        request: Request,
        context: Context
    ) async throws -> Response {
        guard let user = await sessions.user(for: request) else {
            return .redirect(to: .Route.signIn(returningTo: request.uri.string), type: .found)
        }

        var draft = WantsPage.Draft(title: request.uri.queryParameters.get("title") ?? "")

        if
            let slug = request.uri.queryParameters.get("listing"),
            let listing = try await catalogue.listing(slug: slug)
        {
            draft = .init(title: listing.title, minGrade: listing.grade, maxPriceCents: listing.priceCents)
        }

        return try await wantsPage(user, draft: draft, request: request, context: context)
    }

    /// Handles the removal of one of the account's wants.
    @Sendable
    func removeWant(
        request: Request,
        context: Context
    ) async throws -> Response {
        guard let user = await sessions.user(for: request) else {
            return .redirect(to: .Route.signIn(returningTo: .Route.wants), type: .normal)
        }

        if let id = context.parameters.get("id", as: UUID.self) {
            try await collecting.removeWant(id, of: user)
        }

        return .redirect(to: .Route.wants, type: .normal)
    }

    /// Handles the switching of a want's alerts.
    @Sendable
    func toggleAlerts(
        request: Request,
        context: Context
    ) async throws -> Response {
        guard let user = await sessions.user(for: request) else {
            return .redirect(to: .Route.signIn(returningTo: .Route.wants), type: .normal)
        }

        if let id = context.parameters.get("id", as: UUID.self) {
            try await collecting.toggleAlerts(ofWant: id, of: user)
        }

        return .redirect(to: .Route.wants, type: .normal)
    }

    /// Handles a request for the want list. Looking at it is what makes its matches no longer new.
    @Sendable
    func wants(
        request: Request,
        context: Context
    ) async throws -> Response {
        guard let user = await sessions.user(for: request) else {
            return .redirect(to: .Route.signIn(returningTo: .Route.wants), type: .found)
        }

        return try await wantsPage(user, draft: nil, request: request, context: context)
    }

    /// Renders the want list with its matches still marked new, then marks them seen — so the header's bell is quiet on the next page.
    func wantsPage(
        _ user: User,
        draft: WantsPage.Draft?,
        request: Request,
        context: Context
    ) async throws -> Response {
        let wants = try await collecting.wants(of: user)

        try await collecting.markWantsSeen(by: user)

        let viewer = await sessions.viewer(for: request)

        return HTMLResponse(additionalHeaders: .perViewer) { [analytics, assetVersion] in
            WantsPage(
                wants: wants,
                draft: draft,
                viewer: viewer,
                assetVersion: assetVersion,
                analytics: analytics
            )
        }
        .response(from: request, context: context)
    }

}

// MARK: - Series

private extension CollectingController {

    /// Handles a request for the comparison of the copies named in the query, up to three.
    @Sendable
    func compare(
        request: Request,
        context: Context
    ) async throws -> HTMLResponse {
        var copies = [Listing]()

        for slug in request.uri.queryParameters.getAll("copy").prefix(SeriesPage.maxCompared) {
            if let copy = try await catalogue.listing(slug: slug), copy.isAvailable {
                copies.append(copy)
            }
        }

        let viewer = await sessions.viewer(for: request)

        return .init(additionalHeaders: .perViewer) { [analytics, assetVersion, copies] in
            ComparePage(
                copies: copies,
                viewer: viewer,
                assetVersion: assetVersion,
                analytics: analytics
            )
        }
    }

    /// Handles a request for a series; an unknown slug is not found.
    @Sendable
    func series(
        request: Request,
        context: Context
    ) async throws -> HTMLResponse {
        let slug = try context.parameters.require("slug")

        guard let series = try await collecting.series(slug: slug) else {
            throw HTTPError(.notFound)
        }

        // Every copy of the series, wherever it ships from: a series screen is the whole market for it.
        let listings = try await catalogue.listings().filter { $0.seriesSlug == slug }
        let issue = request.uri.queryParameters.get("issue", as: Int.self)
        let viewer = await sessions.viewer(for: request)

        return .init(additionalHeaders: .perViewer) { [analytics, assetVersion] in
            SeriesPage(
                series: series,
                listings: listings,
                issue: issue,
                viewer: viewer,
                assetVersion: assetVersion,
                analytics: analytics
            )
        }
    }

    /// Handles a request for the series index.
    @Sendable
    func seriesIndex(
        request: Request,
        context: Context
    ) async throws -> HTMLResponse {
        let listings = try await catalogue.listings()
        let entries = try await collecting.allSeries().map { series in
            (series, listings.filter { $0.seriesSlug == series.slug })
        }
        let viewer = await sessions.viewer(for: request)

        return .init(additionalHeaders: .perViewer) { [analytics, assetVersion] in
            SeriesIndexPage(
                entries: entries,
                viewer: viewer,
                assetVersion: assetVersion,
                analytics: analytics
            )
        }
    }

}

// MARK: - Structs

/// The fields the add-a-want form posts.
private struct WantForm: Decodable {
    let title: String
    let minGrade: String?
    let maxPrice: String?
    let slabbed: String?

    enum CodingKeys: String, CodingKey {
        case title
        case minGrade = "min-grade"
        case maxPrice = "max-price"
        case slabbed
    }
}