import Elementary
import Foundation
import Infrastructure
import Persistence

/// A sale record, as one of its parties sees it: what was agreed, the five-step handshake, and the step that is theirs to take.
struct SalePage {

    // MARK: Properties

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

    /// The moment stamps are read relative to.
    let now: Date

    /// The party the viewer is to the sale.
    let role: Sale.Role

    /// The sale shown.
    let sale: Sale

    /// The signed-in viewer.
    let viewer: Viewer?

    // MARK: Initializers

    /// Creates the sale record's screen.
    /// - Parameters:
    ///   - sale: the sale shown.
    ///   - role: the party the viewer is to the sale.
    ///   - viewer: the signed-in viewer.
    ///   - now: the moment stamps are read relative to; the present by default.
    ///   - 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(
        sale: Sale,
        role: Sale.Role,
        viewer: Viewer? = nil,
        now: Date = .init(),
        assetVersion: String? = nil,
        analytics: Analytics? = nil
    ) {
        self.analytics = analytics
        self.assetVersion = assetVersion
        self.locale = .init(identifier: "en")
        self.now = now
        self.role = role
        self.sale = sale
        self.viewer = viewer
    }

}

// MARK: - Page

extension SalePage: Page {

    // MARK: Computed

    var content: some HTML {
        SiteLayout(viewer: viewer) {
            div(.class("page sale")) {
                nav(
                    .class("breadcrumb"),
                    .custom(name: "aria-label", value: "Breadcrumb")
                ) {
                    a(.href(role == .buyer ? .Route.messages : .Route.sellerDashboard)) {
                        role == .buyer ? "Messages" : "Seller dashboard"
                    }
                    span(.custom(name: "aria-hidden", value: "true")) {
                        "/"
                    }
                    span(
                        .class("breadcrumb__current"),
                        .custom(name: "aria-current", value: "page")
                    ) {
                        sale.reference
                    }
                }
                div(.class("sale__head")) {
                    div(.class("sale__heading")) {
                        p(.class("type-eyebrow")) {
                            "Sale record · \(sale.reference) · you are the \(role == .buyer ? "buyer" : "seller")"
                        }
                        h1(.class("type-h1")) {
                            "\(sale.listing.title), \(sale.listing.chip.label)"
                        }
                        p(.class("type-body-sm sale__summary")) {
                            "Agreed \(sale.agreedAt.stamp(relativeTo: now)) with \(counterparty) · \(sale.priceCents.euros) + \(sale.shippingCents.euros) tracked shipping · paid off-platform"
                        }
                    }
                    Chip(sale.status.label, tone: sale.status.tone)
                }
                div(.class("card sale__handshake")) {
                    ol(.class("stepper")) {
                        for step in Sale.Step.allCases {
                            li(.class("stepper__step stepper__step--\(state(of: step))")) {
                                span(.class("stepper__dot")) {
                                    if step <= sale.completed {
                                        Icon(.check, size: 14)
                                    } else {
                                        "\(step.rawValue)"
                                    }
                                }
                                span(.class("stepper__name")) {
                                    step.label
                                }
                                span(.class("type-small")) {
                                    caption(of: step)
                                }
                            }
                        }
                    }
                    div(.class("sale__next")) {
                        p(.class("sale__rule")) {
                            "Each step is stamped by the person who did it. Ratings unlock only after "
                            strong {
                                "Received"
                            }
                            ", so every rating on CCN maps to a finished sale."
                        }
                        div(.class("sale__actions")) {
                            action
                            a(
                                .class("button button--outline"),
                                .href(.Route.conversation(sale.conversationID))
                            ) {
                                Icon(.message, size: 15)
                                "Message \(role == .buyer ? "seller" : "buyer")"
                            }
                        }
                    }
                }
                div(.class("sale__body")) {
                    div(.class("sale__column")) {
                        section(.class("card sale__card")) {
                            h2(.class("type-eyebrow sale__title")) {
                                role == .buyer ? "What you agreed to" : "What was agreed"
                            }
                            div(.class("sale__agreed")) {
                                Cover(sale.listing.cover, modifier: "cover--agreed")
                                dl(.class("details")) {
                                    for detail in details {
                                        dt {
                                            detail.term
                                        }
                                        dd {
                                            detail.value
                                        }
                                    }
                                }
                            }
                            p(.class("gate-note")) {
                                Icon(.info, size: 16)
                                span {
                                    "The declared condition above is frozen at the moment of agreement. If the copy arrives with a defect not listed here, that's the basis for a problem report."
                                }
                            }
                        }
                        section(.class("card sale__card")) {
                            h2(.class("type-eyebrow sale__title")) {
                                "Payment · off-platform"
                            }
                            p(.class("type-body-sm sale__text")) {
                                payment
                            }
                        }
                    }
                    div(.class("sale__column")) {
                        section(.class("card sale__card")) {
                            h2(.class("type-eyebrow sale__title")) {
                                role == .buyer ? "Seller" : "Buyer"
                            }
                            if role == .buyer {
                                div(.class("sale__party")) {
                                    span(.class("monogram")) {
                                        sale.listing.shop.monogram
                                    }
                                    div {
                                        p(.class("sale__party-name")) {
                                            sale.listing.shop.name
                                        }
                                        p(.class("type-small")) {
                                            sale.listing.shop.standing
                                        }
                                    }
                                }
                                a(
                                    .class("button button--outline"),
                                    .href(sale.listing.shop.path)
                                ) {
                                    "Visit shop"
                                }
                            } else {
                                div(.class("sale__party")) {
                                    span(.class("monogram")) {
                                        Viewer(sale.buyer).initials
                                    }
                                    p(.class("sale__party-name")) {
                                        sale.buyer.displayName
                                    }
                                }
                            }
                        }
                        if sale.buyerRating != nil || sale.sellerRating != nil {
                            section(.class("card sale__card")) {
                                h2(.class("type-eyebrow sale__title")) {
                                    "Ratings"
                                }
                                dl(.class("details")) {
                                    dt {
                                        "Buyer rated seller"
                                    }
                                    dd {
                                        Self.stars(sale.buyerRating)
                                    }
                                    dt {
                                        "Seller rated buyer"
                                    }
                                    dd {
                                        Self.stars(sale.sellerRating)
                                    }
                                }
                            }
                        }
                    }
                }
            }
        }
    }

    @HTMLBuilder
    var metadata: some HTML {
        meta(
            .name("robots"),
            .content("noindex")
        )
        siteMetadata
    }

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

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

    var title: String {
        "Sale record \(sale.reference) — CCN"
    }

}

// MARK: - Helpers

private extension SalePage {

    // MARK: Computed

    /// The step that is the viewer's to take now, as a form; or what is waited on.
    @HTMLBuilder
    var action: some HTML {
        if sale.allows(.markPaid(note: ""), by: role) {
            step("paid", button: "Mark as paid") {
                noteField("How you paid", placeholder: "Bank transfer (iDEAL)")
            }
        } else if sale.allows(.markSent(note: ""), by: role) {
            step("sent", button: "Mark as sent") {
                noteField("Carrier and tracking", placeholder: "DHL · 3SABCD1234567")
            }
        } else if sale.allows(.markReceived, by: role) {
            step("received", button: "Mark as received") {}
        } else if sale.allows(.rate(stars: 5), by: role) {
            step("rated", button: "Leave rating") {
                fieldset(.class("rating")) {
                    legend(.class("visually-hidden")) {
                        "Your rating, out of five"
                    }
                    for stars in (1...5).reversed() {
                        label(.class("rating__option")) {
                            input(
                                .type(.radio),
                                .name("stars"),
                                .value("\(stars)"),
                                .required
                            )
                            .attributes(.checked, when: stars == 5)
                            span {
                                "\(stars) ★"
                            }
                        }
                    }
                }
            }
        } else {
            p(.class("sale__waiting")) {
                waiting
            }
        }
    }

    /// The other party's name.
    var counterparty: String {
        role == .buyer ? sale.listing.shop.name : sale.buyer.displayName
    }

    /// What was agreed, leaving out what the declaration does not state.
    var details: [(term: String, value: String)] {
        let price = sale.priceCents == sale.askedCents
            ? "\(sale.priceCents.euros) · bought at the asking price"
            : "\(sale.priceCents.euros) · offer accepted (asked \(sale.askedCents.euros))"

        return [
            ("Grade", sale.declared.grade),
            ("Page quality", sale.declared.pageQuality),
            ("Printing", sale.declared.printing),
            ("Declared by seller", sale.declared.notes),
            ("Price", price),
            ("Shipping", "\(sale.shippingCents.euros) · tracked to NL · \(sale.listing.shop.handlingDays) business days handling"),
        ].compactMap { term, value in
            value.map { (term, $0) }
        }
    }

    /// Where the payment stands, in a sentence or two.
    var payment: String {
        let parties = role == .buyer ? "You and the seller settle" : "You and the buyer settle"

        guard let paidAt = sale.paidAt else {
            return "\(parties) payment directly — CCN handles no money. The buyer marks the sale paid here once the transfer is made, so the seller can dispatch."
        }

        let note = sale.paymentNote.map { " by \($0)" } ?? ""

        return "\(parties) payment directly. The buyer marked this as paid\(note) \(paidAt.stamp(relativeTo: now)). CCN keeps the agreed amounts and the stamps as the record of the sale."
    }

    /// What is waited on when the next step is not the viewer's.
    var waiting: String {
        switch sale.next {
        case .paid: "Waiting for the buyer to pay and mark the sale paid."
        case .sent: "Waiting for the seller to dispatch."
        case .received: "Waiting for the buyer to confirm the copy arrived."
        case .rated: "Thanks for rating. Waiting for the other side's rating."
        default: "The handshake is complete."
        }
    }

    // MARK: Methods

    /// The line under a step: its stamp once taken, else who takes it.
    func caption(
        of step: Sale.Step
    ) -> String {
        switch step {
        case .agreed:
            return sale.agreedAt.stamp(relativeTo: now)
        case .paid:
            return sale.paidAt.map { "Buyer marked paid · \($0.stamp(relativeTo: now))" } ?? "Buyer confirms"
        case .sent:
            return sale.sentAt.map { "\(sale.shippingNote ?? "Seller marked sent") · \($0.stamp(relativeTo: now))" } ?? "Seller confirms"
        case .received:
            return sale.receivedAt.map { "Buyer confirmed · \($0.stamp(relativeTo: now))" } ?? "Buyer confirms"
        case .rated:
            let count = [sale.buyerRating, sale.sellerRating].compactMap(\.self).count

            return count == 0 ? "Both sides" : "\(count) of 2 rated"
        }
    }

    /// A short text field for a step's note.
    func noteField(
        _ title: String,
        placeholder: String
    ) -> some HTML {
        label(.class("sale__note")) {
            span(.class("visually-hidden")) {
                title
            }
            input(
                .class("input"),
                .type(.text),
                .name("note"),
                .placeholder(placeholder),
                .custom(name: "maxlength", value: "200")
            )
        }
    }

    /// A rating as stars, or that it is still to come.
    static func stars(
        _ rating: Int?
    ) -> String {
        rating.map { String(repeating: "★", count: $0) + String(repeating: "☆", count: 5 - $0) } ?? "Not yet"
    }

    /// Whether a step is done, the one waited on, or still to come.
    func state(
        of step: Sale.Step
    ) -> String {
        if step <= sale.completed {
            return "done"
        }

        return step == sale.next ? "current" : "pending"
    }

    /// The form taking a step of the handshake.
    func step(
        _ name: String,
        button title: String,
        @HTMLBuilder fields: () -> some HTML
    ) -> some HTML {
        form(
            .class("sale__step"),
            .action(.Route.sale(sale.number)),
            .method(.post)
        ) {
            input(
                .type(.hidden),
                .name("step"),
                .value(name)
            )
            fields()
            button(
                .class("button button--primary"),
                .type(.submit)
            ) {
                title
            }
        }
    }

}