import Elementary
import Foundation
import Infrastructure
import Persistence

/// The listing detail screen: one copy, its price and gated actions, its seller, and its declared details.
struct ListingPage {

    // MARK: Properties

    let analytics: Analytics?
    let assetVersion: String?
    let locale: Locale

    /// The listing shown.
    let listing: Listing

    /// The number of other copies of the same title for sale: in this shop, and across the site.
    let otherCopies: (inShop: Int, everywhere: Int)

    /// The upcoming events the shop trades at, where the copy can be picked up.
    let pickups: [Event]

    /// Other listings from the same shop.
    let related: [Listing]

    /// The signed-in viewer, or `nil` when signed out.
    let viewer: Viewer?

    // MARK: Initializers

    /// Creates the detail screen of a listing.
    /// - Parameters:
    ///   - listing: the listing shown.
    ///   - related: other listings from the same shop.
    ///   - pickups: the upcoming events the shop trades at; none by default.
    ///   - otherCopies: the number of other copies of the same title for sale, in this shop and across the site; none by default.
    ///   - viewer: the signed-in viewer, or `nil` (the default) when signed out.
    ///   - assetVersion: the version token appended to the page's asset URLs, or `nil` (the default) to leave them unversioned.
    ///   - analytics: the analytics tracker embedded in the document head, or `nil` (the default) to omit it.
    init(
        listing: Listing,
        related: [Listing],
        pickups: [Event] = [],
        otherCopies: (inShop: Int, everywhere: Int) = (0, 0),
        viewer: Viewer? = nil,
        assetVersion: String? = nil,
        analytics: Analytics? = nil
    ) {
        self.viewer = viewer
        self.analytics = analytics
        self.assetVersion = assetVersion
        self.listing = listing
        self.locale = .init(identifier: "en")
        self.otherCopies = otherCopies
        self.pickups = pickups
        self.related = related
    }

}

// MARK: - Page

extension ListingPage: Page {

    // MARK: Computed

    var content: some HTML {
        SiteLayout(
            active: listing.kind,
            viewer: viewer
        ) {
            div(.class("page listing")) {
                breadcrumb
                div(.class("listing__body")) {
                    div(.class("listing__media")) {
                        ListingImage(listing, modifier: "cover--hero")
                        if listing.photos.count > 1 {
                            ul(.class("listing__photos")) {
                                ForEach(Array(listing.photos.dropFirst())) { photo in
                                    li {
                                        img(
                                            .class("photo"),
                                            .src(photo),
                                            .alt("Another photo of \(listing.title)"),
                                            .custom(name: "loading", value: "lazy")
                                        )
                                    }
                                }
                            }
                        }
                    }
                    div(.class("listing__main")) {
                        div(.class("listing__intro")) {
                            div(.class("listing__chips")) {
                                Chip(
                                    listing.chip.label,
                                    tone: listing.chip.tone,
                                    isCertified: listing.chip.isCertified
                                )
                                if let pageQuality = listing.pageQuality {
                                    Chip("\(pageQuality) pages")
                                }
                                Chip(listing.printing)
                            }
                            h1(.class("type-h1")) {
                                listing.title
                            }
                            p(.class("listing__byline")) {
                                "\(listing.publisher) · \(listing.year) · \((listing.kind?.singular ?? listing.format).lowercased()) · "
                                a(
                                    .class("listing__series"),
                                    .href(.Route.series(listing.seriesSlug, issue: listing.issueNumber) + (listing.issueNumber == nil ? "" : "#copies"))
                                ) {
                                    listing.issueNumber == nil ? "\(listing.seriesName) series" : "\(listing.seriesName) series · compare copies"
                                }
                            }
                        }
                        buyBox
                        seller
                        section(.class("listing__section")) {
                            h2(.class("type-eyebrow")) {
                                "Details"
                            }
                            dl(.class("details")) {
                                for detail in details {
                                    dt {
                                        detail.term
                                    }
                                    dd {
                                        detail.value
                                    }
                                }
                            }
                        }
                        section(.class("listing__section")) {
                            h2(.class("type-eyebrow")) {
                                "Seller's notes"
                            }
                            p(.class("listing__notes")) {
                                listing.sellerNotes
                            }
                        }
                    }
                }
                if !related.isEmpty {
                    section(.class("listing__related")) {
                        div(.class("section-head")) {
                            h2(.class("type-h2")) {
                                "More from \(listing.shop.name)"
                            }
                            a(
                                .class("link-ink"),
                                .href(listing.shop.path)
                            ) {
                                "Visit the shop"
                            }
                        }
                        div(.class("card-grid")) {
                            for listing in related {
                                ListingCard(listing, context: .shop)
                            }
                        }
                    }
                }
            }
        }
    }

    var scripts: [any Asset] {
        [StaticFile.shared]
    }

    var stylesheets: [any Asset] {
        [StaticFile.shared, StaticFile.listing]
    }

    var summary: String? {
        "\(listing.title), \(listing.chip.label), \(listing.priceCents.euros) from \(listing.shop.name) on CCN."
    }

    var title: String {
        "\(listing.title) · \(listing.chip.label) — CCN"
    }

}

// MARK: - Helpers

private extension ListingPage {

    // MARK: Computed

    var breadcrumb: some HTML {
        nav(
            .class("breadcrumb"),
            .custom(name: "aria-label", value: "Breadcrumb")
        ) {
            a(.href(.Route.home)) {
                "Home"
            }
            if let format = listing.kind {
                span(.custom(name: "aria-hidden", value: "true")) {
                    "/"
                }
                a(.href(format.path)) {
                    format.label
                }
            }
            span(.custom(name: "aria-hidden", value: "true")) {
                "/"
            }
            a(.href(
                SearchParameters()
                    .setting(.publisher, to: listing.publisher)
                    .path(.Route.search)
            )) {
                listing.publisher
            }
            span(.custom(name: "aria-hidden", value: "true")) {
                "/"
            }
            span(
                .class("breadcrumb__current"),
                .custom(name: "aria-current", value: "page")
            ) {
                listing.title
            }
        }
    }

    /// The price and the actions. Every action is gated: signed out, each leads to the sign-in screen and back here.
    var buyBox: some HTML {
        div(.class("card buy-box")) {
            div(.class("buy-box__head")) {
                div(.class("buy-box__price")) {
                    span(.class("type-price")) {
                        listing.priceCents.euros
                    }
                    span(.class("type-body-sm buy-box__terms")) {
                        "+ \(listing.shippingCents.euros) tracked shipping to NL"
                        listing.acceptsOffers ? " · accepts offers" : ""
                        if let event = pickups.first {
                            " · "
                            a(
                                .class("listing__series"),
                                .href(.Route.events)
                            ) {
                                "or pick up at \(event.name), \(Date.span(from: event.startsOn, to: event.endsOn))"
                            }
                        }
                    }
                }
                a(
                    .class("button button--sm"),
                    .href(.Route.newWant(listing: listing.slug))
                ) {
                    Icon(.bookmark, size: 16)
                    "Save"
                }
            }
            if !listing.isAvailable {
                div(.class("notice listing__sold")) {
                    p {
                        strong {
                            "This copy sold\(listing.soldAt.map { " on \($0.dayStamp)" } ?? "")."
                        }
                        " \(listing.shop.name) has \(otherCopies.inShop) more \(otherCopies.inShop == 1 ? "copy" : "copies") of \(listing.title), and \(otherCopies.everywhere) \(otherCopies.everywhere == 1 ? "is" : "are") listed across CCN."
                    }
                    div(.class("empty__actions")) {
                        a(
                            .class("button button--primary button--sm"),
                            .href(SearchParameters().setting(.query, to: listing.title).setting(.shipsFrom, to: "anywhere").path(.Route.search))
                        ) {
                            "Other copies"
                        }
                        a(
                            .class("button button--outline button--sm"),
                            .href(.Route.newWant(title: listing.title))
                        ) {
                            Icon(.bell, size: 15)
                            "Alert me"
                        }
                    }
                }
            } else if viewer?.shopSlug == listing.shop.slug {
                p(.class("notice")) {
                    "This is your listing. Offers on it arrive in your "
                    a(.href(.Route.sellerDashboard)) {
                        "seller dashboard"
                    }
                    "."
                }
            } else {
                actions
            }
        }
    }

    /// The gated actions: buy, offer, message — and, signed out, why they lead to the sign-in.
    @HTMLBuilder
    var actions: some HTML {
        div(.class("buy-box__actions")) {
            a(
                .class("button button--primary button--lg"),
                .href(gated(.Route.buy(listing.slug)))
            ) {
                "Buy now"
            }
            if listing.acceptsOffers {
                a(
                    .class("button button--outline button--lg"),
                    .href(gated(.Route.offer(listing.slug)))
                ) {
                    "Make an offer"
                }
            }
            a(
                .class("button button--bare button--lg"),
                .href(gated(.Route.message(listing: listing.slug)))
            ) {
                Icon(.message, size: 16)
                "Message seller"
            }
        }
        if viewer == nil {
            p(.class("gate-note")) {
                Icon(.lock, size: 16)
                span {
                    "Buying, offers, saving and messages need a signed-in account. "
                    a(
                        .class("gate-note__link"),
                        .href(.Route.signIn(returningTo: listing.path))
                    ) {
                        "Sign in or join with a passkey"
                    }
                    " — browsing stays open to everyone."
                }
            }
        }
    }

    /// The declared details, leaving out what the listing does not state.
    var details: [(term: String, value: String)] {
        var grade = listing.chip.label

        if let certNumber = listing.certNumber {
            grade += " · cert \(certNumber)"
        } else if listing.grade != nil {
            grade += " · graded by the seller against the public grading guide"
        }

        return [
            ("Title", listing.seriesTitle),
            ("Issue", listing.issueLabel),
            ("Publisher", listing.publisher),
            ("Printing", listing.printingDetail),
            (listing.grade == nil ? "Condition" : "Grade", grade),
            ("Page quality", listing.pageQuality),
            ("Declared defects", listing.defects.isEmpty ? nil : listing.defects.joined(separator: "; ")),
            ("Key notes", listing.keyNotes),
            ("Ships", "\(listing.shop.shipsNote.prefix(1).uppercased())\(listing.shop.shipsNote.dropFirst()) · \(listing.shop.handlingDays) business days handling"),
        ].compactMap { term, value in
            value.map { (term, $0) }
        }
    }

    var seller: some HTML {
        div(.class("seller")) {
            span(.class("monogram monogram--lg")) {
                listing.shop.monogram
            }
            div(.class("seller__text")) {
                div(.class("seller__name")) {
                    a(.href(listing.shop.path)) {
                        listing.shop.name
                    }
                    if listing.shop.isVerified {
                        span(.class("verified")) {
                            Icon(.check, size: 12)
                            "Verified shop"
                        }
                    }
                }
                span(.class("type-caption")) {
                    listing.shop.standing
                }
            }
            a(
                .class("button button--outline button--sm"),
                .href(listing.shop.path)
            ) {
                "Visit shop"
            }
        }
    }

    // MARK: Methods

    /// The path a gated action on this listing leads to.
    func gated(
        _ path: String
    ) -> String {
        .Route.gated(path, from: listing.path, viewer: viewer)
    }

}