import Elementary
import Foundation
import Infrastructure
import Persistence

/// A series: its issues with what is listed of each — and what is not, one tap from an alert — the copies of one issue, and its collected editions.
struct SeriesPage {

    // MARK: Properties

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

    /// The issue whose copies are listed, or `nil` for none.
    let issue: Int?

    /// Every listing of the series still for sale.
    let listings: [Listing]

    /// The issues the viewer owns of the series, or `nil` signed out.
    let owned: Set<Int>?

    /// The series shown.
    let series: Series

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

    // MARK: Initializers

    /// Creates a series' screen.
    /// - Parameters:
    ///   - series: the series shown.
    ///   - listings: every listing of the series still for sale.
    ///   - issue: the issue whose copies are listed, or `nil` (the default) for none.
    ///   - owned: the issues the viewer owns of the series, or `nil` (the default) signed out.
    ///   - 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(
        series: Series,
        listings: [Listing],
        issue: Int? = nil,
        owned: Set<Int>? = nil,
        viewer: Viewer? = nil,
        assetVersion: String? = nil,
        analytics: Analytics? = nil
    ) {
        self.analytics = analytics
        self.assetVersion = assetVersion
        self.issue = issue
        self.listings = listings
        self.locale = .init(identifier: "en")
        self.owned = owned
        self.series = series
        self.viewer = viewer
    }

}

// MARK: - Page

extension SeriesPage: Page {

    // MARK: Constants

    /// The most copies compared side by side.
    static let maxCompared = 3

    // MARK: Computed

    var content: some HTML {
        SiteLayout(viewer: viewer) {
            div(.class("page series")) {
                nav(
                    .class("breadcrumb"),
                    .custom(name: "aria-label", value: "Breadcrumb")
                ) {
                    a(.href(.Route.home)) {
                        "Home"
                    }
                    span(.custom(name: "aria-hidden", value: "true")) {
                        "/"
                    }
                    a(.href(.Route.series)) {
                        "Series"
                    }
                    span(.custom(name: "aria-hidden", value: "true")) {
                        "/"
                    }
                    span(
                        .class("breadcrumb__current"),
                        .custom(name: "aria-current", value: "page")
                    ) {
                        series.name
                    }
                }
                section(.class("series__head")) {
                    if let cover = listings.first(where: { $0.issueNumber != nil }) ?? listings.first {
                        ListingImage(cover, modifier: "cover--series")
                    }
                    div(.class("series__intro")) {
                        p(.class("type-eyebrow")) {
                            "Series · \(series.publisher) · \(series.years)\(series.issueCount > 0 ? " · \(series.issueCount) issues" : "")"
                        }
                        h1(.class("type-h1")) {
                            series.name
                        }
                        p(.class("type-lead")) {
                            "\(series.blurb)\(series.blurb.isEmpty ? "" : " ")\(listings.count) \(listings.count == 1 ? "copy" : "copies") listed across CCN right now."
                        }
                        if let owned, series.issueCount > 0 {
                            div(.class("card series__collection")) {
                                p(.class("type-eyebrow")) {
                                    "Your collection"
                                }
                                p(.class("type-panel")) {
                                    "\(owned.count) of \(series.issueCount) owned"
                                }
                                p(.class("type-small")) {
                                    "\(gaps.count) missing · \(gaps.filter { !$0.copies.isEmpty }.count) of them listed now"
                                }
                            }
                        }
                        ul(.class("series__keys")) {
                            ForEach(keys) { key in
                                li(.class("chip chip--warn")) {
                                    "#\(key.issue) · \(key.notes)"
                                }
                            }
                        }
                    }
                }
                if !issues.isEmpty {
                    section(.class("series__section")) {
                        div(.class("section-head")) {
                            h2(.class("type-h2")) {
                                series.issueCount > 0 ? "All \(series.issueCount) issues" : "Issues listed"
                            }
                            span(.class("type-small")) {
                                "Cheapest listed copy per issue"
                            }
                        }
                        ol(.class("series__issues")) {
                            ForEach(issues) { entry in
                                li(.class(issueClass(entry))) {
                                    span(.class("series__number")) {
                                        "#\(entry.number)"
                                    }
                                    if let cheapest = entry.copies.min(by: { $0.priceCents < $1.priceCents }) {
                                        a(.href(.Route.series(series.slug, issue: entry.number) + "#copies")) {
                                            "\(entry.copies.count) listed · from \(cheapest.priceCents.euros)"
                                        }
                                        .attributes(.custom(name: "aria-current", value: "true"), when: entry.number == issue)
                                    } else {
                                        a(.href(.Route.gated(
                                            .Route.newWant(title: "\(series.name) #\(entry.number)"),
                                            from: .Route.series(series.slug),
                                            viewer: viewer
                                        ))) {
                                            "None listed · alert me"
                                        }
                                    }
                                    if let owned {
                                        form(
                                            .action("\(String.Route.series(series.slug))/own"),
                                            .method(.post)
                                        ) {
                                            input(
                                                .type(.hidden),
                                                .name("issue"),
                                                .value("\(entry.number)")
                                            )
                                            button(
                                                .class("series__own"),
                                                .type(.submit),
                                                .custom(name: "aria-pressed", value: owned.contains(entry.number) ? "true" : "false")
                                            ) {
                                                owned.contains(entry.number) ? "Owned ✓" : "I own this"
                                            }
                                        }
                                    }
                                }
                            }
                        }
                    }
                }
                if let issue, !copies.isEmpty {
                    section(
                        .class("series__section"),
                        .id("copies")
                    ) {
                        h2(.class("type-h2")) {
                            "Copies of #\(issue) — \(copies.count) listed"
                        }
                        // A plain `GET` form: the copies ticked become the comparison's query.
                        form(
                            .class("series__copies"),
                            .action(.Route.compare),
                            .method(.get)
                        ) {
                            div(.class("table-scroll")) {
                                table(.class("table")) {
                                    thead {
                                        tr {
                                            th {
                                                span(.class("visually-hidden")) {
                                                    "Compare"
                                                }
                                            }
                                            ForEach(["Grade", "Printing", "Pages", "Defects", "Price", "Ship to NL", "Shop", ""]) { heading in
                                                th {
                                                    heading
                                                }
                                            }
                                        }
                                    }
                                    tbody {
                                        ForEach(copies) { copy in
                                            tr {
                                                td {
                                                    input(
                                                        .type(.checkbox),
                                                        .name("copy"),
                                                        .value(copy.slug),
                                                        .custom(name: "aria-label", value: "Compare the \(copy.chip.label) from \(copy.shop.name)")
                                                    )
                                                }
                                                td {
                                                    Chip(copy.chip.label, tone: copy.chip.tone, isCertified: copy.chip.isCertified)
                                                }
                                                td {
                                                    copy.printing
                                                }
                                                td {
                                                    copy.pageQuality ?? "—"
                                                }
                                                td {
                                                    copy.defects.isEmpty ? "None declared" : copy.defects.joined(separator: "; ")
                                                }
                                                td {
                                                    strong {
                                                        copy.priceCents.euros
                                                    }
                                                }
                                                td {
                                                    "\(copy.shippingCents.euros) · \(copy.shop.country)"
                                                }
                                                td {
                                                    a(.href(copy.shop.path)) {
                                                        copy.shop.name
                                                    }
                                                }
                                                td {
                                                    a(
                                                        .class("link-ink"),
                                                        .href(copy.path)
                                                    ) {
                                                        "View"
                                                    }
                                                }
                                            }
                                        }
                                    }
                                }
                            }
                            button(
                                .class("button button--dark"),
                                .type(.submit)
                            ) {
                                "Compare the copies ticked (up to \(Self.maxCompared))"
                            }
                        }
                    }
                }
                if !collected.isEmpty {
                    section(.class("series__section")) {
                        h2(.class("type-h2")) {
                            "Collected editions"
                        }
                        div(.class("card-grid")) {
                            ForEach(collected) { listing in
                                ListingCard(listing)
                            }
                        }
                    }
                }
            }
        }
    }

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

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

    var summary: String? {
        "\(series.name), \(series.publisher), \(series.years): every issue, the copies listed of each, and the gaps."
    }

    var title: String {
        "\(series.name) — CCN"
    }

}

// MARK: - Helpers

private extension SeriesPage {

    /// The issues of the run the viewer does not own.
    var gaps: [(number: Int, copies: [Listing])] {
        issues.filter { !(owned ?? []).contains($0.number) }
    }

    /// An issue's tile: a gap reads quieter, and an owned issue is dimmed.
    func issueClass(
        _ entry: (number: Int, copies: [Listing])
    ) -> String {
        [
            "series__issue",
            entry.copies.isEmpty ? "series__issue--gap" : nil,
            owned?.contains(entry.number) == true ? "series__issue--owned" : nil,
        ]
        .compactMap(\.self)
        .joined(separator: " ")
    }

    /// The series' manga, trade paperbacks, and hardcovers.
    var collected: [Listing] {
        listings.filter { $0.issueNumber == nil }
    }

    /// The copies of the issue picked, cheapest delivered first.
    var copies: [Listing] {
        listings
            .filter { $0.issueNumber == issue }
            .sorted { $0.priceCents + $0.shippingCents < $1.priceCents + $1.shippingCents }
    }

    /// Every issue of the run with the copies listed of it; for a series without a known run, the issues listed alone.
    var issues: [(number: Int, copies: [Listing])] {
        let listed = Dictionary(grouping: listings.filter { $0.issueNumber != nil }) { $0.issueNumber ?? 0 }
        let numbers = series.issueCount > 0 ? Array(1...series.issueCount) : listed.keys.sorted()

        return numbers.map { ($0, listed[$0] ?? []) }
    }

    /// The key issues, as the listings of them say.
    var keys: [(issue: Int, notes: String)] {
        var seen = Set<Int>()

        return listings
            .compactMap { listing in
                guard let issue = listing.issueNumber, let notes = listing.keyNotes, seen.insert(issue).inserted else {
                    return nil
                }

                return (issue, notes)
            }
            .sorted { $0.issue < $1.issue }
    }

}