import Elementary
import Foundation
import Infrastructure
import Persistence

/// The search results screen: the matching listings beside the filter rail.
struct SearchPage {

    // MARK: Properties

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

    /// The page of listings shown.
    let listings: [Listing]

    /// The number of listings matching the search, across every page.
    let matchCount: Int

    /// The page shown and the number of pages.
    let pages: (current: Int, total: Int)

    /// The search the screen answers.
    let parameters: SearchParameters

    /// Every publisher a listing can be filtered by.
    let publishers: [String]

    /// The number of shops the matching listings come from.
    let shopCount: Int

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

    // MARK: Initializers

    /// Creates the search results screen for a search and the listings matching it.
    /// - Parameters:
    ///   - parameters: the search the screen answers.
    ///   - matches: every listing matching the search; the screen shows the page the parameters ask for.
    ///   - publishers: every publisher a listing can be filtered by.
    ///   - 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(
        parameters: SearchParameters,
        matches: [Listing],
        publishers: [String],
        viewer: Viewer? = nil,
        assetVersion: String? = nil,
        analytics: Analytics? = nil
    ) {
        self.viewer = viewer
        let slice = Pagination.slice(
            matches,
            page: parameters.page,
            size: SearchParameters.pageSize
        )

        self.analytics = analytics
        self.assetVersion = assetVersion
        self.listings = slice.items
        self.locale = .init(identifier: "en")
        self.matchCount = matches.count
        self.pages = (slice.current, slice.total)
        self.parameters = parameters
        self.publishers = publishers
        self.shopCount = Set(matches.map(\.shop.slug)).count
    }

}

// MARK: - Page

extension SearchPage: Page {

    // MARK: Constants

    /// The path the page is served at.
    static let path = String.Route.search

    /// The identifier tying the sort select to the filter form.
    private static let formID = "filters"

    // MARK: Computed

    var content: some HTML {
        SiteLayout(
            active: formats.count == 1 ? formats.first : nil,
            query: parameters.value(.query),
            viewer: viewer
        ) {
            div(.class("page search")) {
                div(.class("search__head")) {
                    div(.class("search__heading")) {
                        p(.class("type-eyebrow")) {
                            formats.isEmpty ? "All formats" : formats.map(\.label).joined(separator: " · ")
                        }
                        h1(.class("type-h1")) {
                            heading
                        }
                        p(.class("type-body-sm search__count")) {
                            matchCount == 1 ? "1 listing" : "\(matchCount) listings"
                            shopCount == 1 ? " from 1 shop" : " from \(shopCount) shops"
                        }
                    }
                    SortSelect(
                        form: Self.formID,
                        selected: parameters.filter.sort
                    )
                }
                div(.class("search__body")) {
                    filters
                    div(.class("search__results")) {
                        if !parameters.pills.isEmpty {
                            ul(.class("search__pills")) {
                                for pill in parameters.pills {
                                    li {
                                        a(
                                            .class("pill pill--active"),
                                            .href(pill.removed.path(Self.path)),
                                            .custom(
                                                name: "aria-label",
                                                value: "Remove filter: \(pill.label)"
                                            )
                                        ) {
                                            pill.label
                                            span(.custom(name: "aria-hidden", value: "true")) {
                                                " ×"
                                            }
                                        }
                                    }
                                }
                            }
                        }
                        if listings.isEmpty {
                            div(.class("empty")) {
                                h2(.class("type-panel")) {
                                    parameters.value(.query).map { "Nothing for “\($0)”" } ?? "No listings match"
                                }
                                p(.class("type-body-sm")) {
                                    "Nothing listed meets that right now. Clear the filters — listings outside the EU are left out by default — or ask to be told when a copy appears."
                                }
                                div(.class("empty__actions")) {
                                    if let query = parameters.value(.query) {
                                        a(
                                            .class("button button--primary"),
                                            .href(.Route.newWant(title: query))
                                        ) {
                                            Icon(.bell, size: 16)
                                            "Alert me"
                                        }
                                    }
                                    a(
                                        .class("button button--outline"),
                                        .href(SearchParameters().setting(.shipsFrom, to: "anywhere").path(Self.path))
                                    ) {
                                        "Clear all filters"
                                    }
                                }
                            }
                        } else {
                            div(.class("card-grid card-grid--search")) {
                                for listing in listings {
                                    ListingCard(listing, context: .search)
                                }
                            }
                        }
                        Pagination(
                            current: pages.current,
                            total: pages.total
                        ) { [parameters] in
                            parameters.setting(.page, to: "\($0)").path(Self.path)
                        }
                    }
                }
            }
        }
    }

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

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

    var title: String {
        "\(heading) — CCN"
    }

}

// MARK: - Helpers

private extension SearchPage {

    // MARK: Computed

    /// The filter rail: a plain `GET` form inside a disclosure, which the stylesheet keeps open on desktop.
    var filters: some HTML {
        details(.class("filters")) {
            Elementary.summary(.class("filters__toggle button button--outline")) {
                Icon(.filter, size: 15)
                parameters.pills.isEmpty ? "Filters" : "Filters · \(parameters.pills.count)"
            }
            form(
                .class("filters__form"),
                .id(Self.formID),
                .action(Self.path),
                .method(.get)
            ) {
                div(.class("filters__head")) {
                    h2(.class("type-eyebrow filters__title")) {
                        "Filters"
                    }
                    a(
                        .class("filters__clear"),
                        .href(Self.path)
                    ) {
                        "Clear all"
                    }
                }
                if let query = parameters.value(.query) {
                    input(
                        .type(.hidden),
                        .name(SearchParameters.Name.query.rawValue),
                        .value(query)
                    )
                }
                group("Format") {
                    ForEach(Format.allCases) { format in
                        checkbox(.format, value: format.rawValue, label: format.label)
                    }
                }
                group("Grading") {
                    checkbox(.grading, value: SearchParameters.Grading.slabbed.rawValue, label: "Slabbed (CGC, CBCS, PGX)")
                    checkbox(.grading, value: SearchParameters.Grading.raw.rawValue, label: "Raw, seller-graded")
                    div(.class("filters__range")) {
                        field(.gradeMin, label: "Min", placeholder: "0.5", isLabelVisible: true)
                        field(.gradeMax, label: "Max", placeholder: "10", isLabelVisible: true)
                    }
                }
                group("Printing") {
                    checkbox(.firstPrint, value: "1", label: "1st print only")
                }
                group("Publisher") {
                    ForEach(publishers) { publisher in
                        checkbox(.publisher, value: publisher, label: publisher)
                    }
                }
                group("Price") {
                    div(.class("filters__range")) {
                        field(.priceMin, label: "Minimum price", placeholder: "€ min")
                        span(.class("type-small")) {
                            "to"
                        }
                        field(.priceMax, label: "Maximum price", placeholder: "€ max")
                    }
                }
                group("Ships from") {
                    div(.class("segmented")) {
                        for region in ListingFilter.Region.allCases {
                            label(.class("segmented__option")) {
                                input(
                                    .type(.radio),
                                    .name(SearchParameters.Name.shipsFrom.rawValue),
                                    .value(region.rawValue)
                                )
                                .attributes(.checked, when: region == parameters.filter.shipsFrom)
                                span {
                                    region == .anywhere ? "Anywhere" : region.rawValue.uppercased()
                                }
                            }
                        }
                    }
                    span(.class("type-small")) {
                        "Outside the EU, import VAT may apply."
                    }
                    checkbox(.pickup, value: parameters.value(.pickup) ?? SearchParameters.anyEvent, label: "Pickup at an event")
                }
                group("Key issues") {
                    checkbox(.keys, value: "1", label: "Key issues only")
                }
                group("Seller") {
                    checkbox(.offers, value: "1", label: "Accepts offers")
                    checkbox(.verified, value: "1", label: "Verified shop")
                }
                button(
                    .class("button button--dark button--block"),
                    .type(.submit)
                ) {
                    "Apply filters"
                }
            }
        }
    }

    /// The formats the search is narrowed to.
    var formats: [Format] {
        parameters
            .values(.format)
            .compactMap(Format.init)
    }

    /// The screen's heading: the search text in quotes, else the one format searched, else every listing.
    var heading: String {
        if let query = parameters.value(.query) {
            return "“\(query)”"
        }

        return formats.count == 1 ? formats[0].label : "All listings"
    }

    // MARK: Methods

    /// A checkbox, ticked when the search carries its pair.
    func checkbox(
        _ name: SearchParameters.Name,
        value: String,
        label text: String
    ) -> some HTML {
        label(.class("check")) {
            input(
                .type(.checkbox),
                .name(name.rawValue),
                .value(value)
            )
            .attributes(.checked, when: parameters.has(name, value: value))
            text
        }
    }

    /// A short text field, filled with the search's value for its name.
    func field(
        _ name: SearchParameters.Name,
        label text: String,
        placeholder: String,
        isLabelVisible: Bool = false
    ) -> some HTML {
        label(.class("filters__field")) {
            span(.class(isLabelVisible ? "type-small" : "visually-hidden")) {
                text
            }
            input(
                .class("input input--sm"),
                .type(.text),
                .name(name.rawValue),
                .value(parameters.value(name) ?? ""),
                .placeholder(placeholder),
                .custom(name: "inputmode", value: "decimal")
            )
        }
    }

    /// A titled group of filter controls.
    func group(
        _ title: String,
        @HTMLBuilder content: () -> some HTML
    ) -> some HTML {
        fieldset(.class("filters__group")) {
            legend(.class("type-label")) {
                title
            }
            content()
        }
    }

}