import Elementary
import Foundation
import Infrastructure
import Persistence

/// Copies side by side: grade, page quality, declared defects, and what each costs delivered to the Netherlands.
struct ComparePage {

    // MARK: Properties

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

    /// The copies compared, cheapest delivered first.
    let copies: [Listing]

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

    // MARK: Initializers

    /// Creates the comparison.
    /// - Parameters:
    ///   - copies: the copies compared, in any order.
    ///   - 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(
        copies: [Listing],
        viewer: Viewer? = nil,
        assetVersion: String? = nil,
        analytics: Analytics? = nil
    ) {
        self.analytics = analytics
        self.assetVersion = assetVersion
        self.copies = copies.sorted { Self.delivered($0) < Self.delivered($1) }
        self.locale = .init(identifier: "en")
        self.viewer = viewer
    }

}

// MARK: - Page

extension ComparePage: Page {

    // MARK: Computed

    var content: some HTML {
        SiteLayout(viewer: viewer) {
            div(.class("page compare")) {
                div(.class("compare__head")) {
                    div(.class("series__intro")) {
                        p(.class("type-eyebrow")) {
                            "Compare · \(copies.first?.title ?? "copies") · \(copies.count) \(copies.count == 1 ? "copy" : "copies")"
                        }
                        h1(.class("type-h1")) {
                            "Which copy?"
                        }
                        p(.class("type-body-sm compare__lead")) {
                            "Grade, page quality, declared defects and total cost delivered to the Netherlands, side by side."
                        }
                    }
                    if let first = copies.first {
                        a(
                            .class("button button--outline"),
                            .href(.Route.series(first.seriesSlug, issue: first.issueNumber))
                        ) {
                            "Back to the series"
                        }
                    }
                }
                if copies.isEmpty {
                    div(.class("empty")) {
                        h2(.class("type-panel")) {
                            "Nothing to compare"
                        }
                        p(.class("type-body-sm")) {
                            "Tick up to \(SeriesPage.maxCompared) copies of an issue on its series page."
                        }
                        a(
                            .class("button button--outline"),
                            .href(.Route.series)
                        ) {
                            "Browse series"
                        }
                    }
                }
                ul(.class("compare__copies")) {
                    ForEach(copies) { copy in
                        li(.class("card compare__copy")) {
                            a(
                                .class("compare__cover"),
                                .href(copy.path),
                                .custom(name: "aria-label", value: "\(copy.title), \(copy.chip.label), from \(copy.shop.name)")
                            ) {
                                ListingImage(copy)
                            }
                            div(.class("compare__price")) {
                                span(.class("type-stat")) {
                                    Self.delivered(copy).euros
                                }
                                Chip(copy.chip.label, tone: copy.chip.tone, isCertified: copy.chip.isCertified)
                            }
                            dl(.class("compare__facts")) {
                                ForEach(Self.facts(of: copy)) { fact in
                                    dt {
                                        fact.term
                                    }
                                    dd {
                                        fact.value
                                    }
                                }
                            }
                            div(.class("compare__actions")) {
                                a(
                                    .class("button button--primary button--sm"),
                                    .href(.Route.gated(.Route.buy(copy.slug), from: copy.path, viewer: viewer))
                                ) {
                                    "Buy now"
                                }
                                a(
                                    .class("button button--outline button--sm"),
                                    .href(copy.path)
                                ) {
                                    "View listing"
                                }
                            }
                        }
                    }
                }
                p(.class("gate-note")) {
                    Icon(.info, size: 16)
                    span {
                        "The delivered price adds each seller's tracked shipping to the Netherlands. Sales from outside the EU may attract import VAT at delivery."
                    }
                }
            }
        }
    }

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

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

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

    var title: String {
        "Compare copies — CCN"
    }

}

// MARK: - Helpers

private extension ComparePage {

    /// What a copy costs delivered to the Netherlands, in euro cents.
    static func delivered(
        _ copy: Listing
    ) -> Int {
        copy.priceCents + copy.shippingCents
    }

    /// What sets a copy apart, row by row.
    static func facts(
        of copy: Listing
    ) -> [(term: String, value: String)] {
        let customs = copy.shop.shipsFromEU ? "" : " · customs may apply"

        return [
            ("Asking", copy.priceCents.euros + (copy.acceptsOffers ? " · accepts offers" : "")),
            ("Page quality", copy.pageQuality ?? "Not stated"),
            ("Printing", copy.printingDetail),
            ("Declared defects", copy.defects.isEmpty ? "None declared" : copy.defects.joined(separator: "; ")),
            ("Ship to NL", "\(copy.shippingCents.euros) tracked · \(copy.shop.handlingDays)-day handling\(customs)"),
            ("Shop", "\(copy.shop.name) · \(copy.shop.location)"),
            ("Rated sales", copy.shop.ratedSales == 0 ? "None yet" : "\(copy.shop.ratedSales) · \(String(format: "%.1f", copy.shop.rating)) · \(copy.shop.returnsNote)"),
        ]
    }

}