import Elementary
import Foundation
import Infrastructure
import Persistence

/// The want list: what the viewer is looking for, the listings that meet each want, and the form adding one.
struct WantsPage {

    // MARK: Properties

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

    /// The values the add-a-want form is filled with, or `nil` to show the list alone.
    let draft: Draft?

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

    /// The viewer's wants, the newest first.
    let wants: [Want]

    // MARK: Initializers

    /// Creates the want list.
    /// - Parameters:
    ///   - wants: the viewer's wants, the newest first.
    ///   - draft: the values the add-a-want form is filled with, or `nil` (the default) to show the list alone.
    ///   - viewer: the signed-in viewer.
    ///   - 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(
        wants: [Want],
        draft: Draft? = nil,
        viewer: Viewer? = nil,
        assetVersion: String? = nil,
        analytics: Analytics? = nil
    ) {
        self.analytics = analytics
        self.assetVersion = assetVersion
        self.draft = draft
        self.locale = .init(identifier: "en")
        self.viewer = viewer
        self.wants = wants
    }

}

// MARK: - Structs

extension WantsPage {
    /// What the add-a-want form is filled with: a listing saved, a gap in a series, or nothing yet.
    struct Draft: Sendable, Equatable {
        var title = ""
        var minGrade: Double?
        var maxPriceCents: Int?
    }
}

// MARK: - Page

extension WantsPage: Page {

    // MARK: Computed

    var content: some HTML {
        SiteLayout(viewer: viewer) {
            div(.class("page wants")) {
                div(.class("section-head")) {
                    h1(.class("type-h1")) {
                        "Wants"
                    }
                    span(.class("type-small")) {
                        "\(wants.count) \(wants.count == 1 ? "want" : "wants") · \(wants.reduce(0) { $0 + $1.newMatchCount }) new matches"
                    }
                }
                if let draft {
                    add(draft)
                }
                if wants.isEmpty, draft == nil {
                    div(.class("empty")) {
                        h2(.class("type-panel")) {
                            "No wants yet"
                        }
                        p(.class("type-body-sm")) {
                            "Add the issues you're hunting. We check every new listing against them and tell you the moment one appears."
                        }
                        p(.class("type-small")) {
                            "Tip: on any series page, a missing issue is one tap from an alert."
                        }
                    }
                }
                ul(.class("wants__list")) {
                    ForEach(wants) { want in
                        li(.class("card wants__want")) {
                            div(.class("wants__top")) {
                                a(
                                    .class("wants__title"),
                                    .href(Self.search(for: want))
                                ) {
                                    want.title
                                }
                                if want.newMatchCount > 0 {
                                    span(.class("wants__new")) {
                                        "\(want.newMatchCount) new"
                                    }
                                } else {
                                    span(.class("type-small")) {
                                        want.matches.isEmpty ? "no matches yet" : "\(want.matches.count) listed"
                                    }
                                }
                            }
                            p(.class("type-small")) {
                                Self.limits(of: want)
                            }
                            if let cheapest = want.matches.min(by: { $0.priceCents < $1.priceCents }) {
                                a(
                                    .class("wants__match"),
                                    .href(cheapest.path)
                                ) {
                                    "From \(cheapest.priceCents.euros) · \(cheapest.chip.label) · \(cheapest.shop.name)"
                                }
                            }
                            div(.class("wants__actions")) {
                                form(
                                    .action("\(String.Route.wants)/\(want.id.uuidString.lowercased())/alerts"),
                                    .method(.post)
                                ) {
                                    button(
                                        .class("switch"),
                                        .type(.submit),
                                        .custom(name: "role", value: "switch"),
                                        .custom(name: "aria-checked", value: want.alerts ? "true" : "false")
                                    ) {
                                        span(.class("switch__track")) {}
                                        "Alert"
                                    }
                                }
                                form(
                                    .action("\(String.Route.wants)/\(want.id.uuidString.lowercased())/remove"),
                                    .method(.post)
                                ) {
                                    button(
                                        .class("button button--bare button--sm"),
                                        .type(.submit)
                                    ) {
                                        "Remove"
                                    }
                                }
                            }
                        }
                    }
                }
                if draft == nil {
                    a(
                        .class("wants__add"),
                        .href(.Route.newWant())
                    ) {
                        "+ Add a want"
                    }
                }
                p(.class("type-small wants__note")) {
                    "Matches are checked every time a listing is published, among copies shipping from the EU. The bell in the header counts the new ones."
                }
            }
        }
    }

    @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 {
        "Want list — CCN"
    }

}

// MARK: - Helpers

private extension WantsPage {

    /// The form adding a want.
    func add(
        _ draft: Draft
    ) -> some HTML {
        form(
            .class("card wants__form"),
            .action(.Route.wants),
            .method(.post)
        ) {
            h2(.class("type-panel")) {
                "Add a want"
            }
            div(.class("listing-form__grid")) {
                TextField(
                    name: "title",
                    title: "Series and issue",
                    value: draft.title,
                    placeholder: "Nightward #7",
                    hint: "Every word has to appear in a listing's title",
                    isWide: true,
                    maxLength: 120
                )
                SelectField(
                    name: "min-grade",
                    title: "Lowest grade",
                    options: [("", "Any grade")] + Grading.scale.map { ($0.grade.oneDecimal, "\($0.grade.oneDecimal) · \($0.code)") },
                    selected: draft.minGrade?.oneDecimal ?? ""
                )
                TextField(
                    name: "max-price",
                    title: "Most you'd pay (EUR)",
                    value: draft.maxPriceCents.map { "\($0 / 100)" } ?? "",
                    placeholder: "40"
                )
                label(.class("check")) {
                    input(
                        .type(.checkbox),
                        .name("slabbed"),
                        .value("1")
                    )
                    "Slabbed copies only"
                }
            }
            div(.class("listing-form__submit")) {
                a(
                    .class("button"),
                    .href(.Route.wants)
                ) {
                    "Cancel"
                }
                button(
                    .class("button button--primary"),
                    .type(.submit)
                ) {
                    "Add to want list"
                }
            }
        }
    }

    /// A want's limits in a line, e.g. `grade ≥ 8.0 · max €40 · ships from EU only`.
    static func limits(
        of want: Want
    ) -> String {
        [
            want.slabbedOnly ? "slabbed only" : nil,
            want.minGrade.map { "grade ≥ \($0.oneDecimal)" },
            want.maxPriceCents.map { "max \($0.euros)" },
            "ships from EU only",
        ]
        .compactMap(\.self)
        .joined(separator: " · ")
    }

    /// The search showing a want's matches.
    static func search(
        for want: Want
    ) -> String {
        var parameters = SearchParameters().setting(.query, to: want.title.replacingOccurrences(of: "·", with: " "))

        if let minGrade = want.minGrade {
            parameters = parameters.setting(.gradeMin, to: minGrade.oneDecimal)
        }

        if let maxPriceCents = want.maxPriceCents {
            parameters = parameters.setting(.priceMax, to: "\(maxPriceCents / 100)")
        }

        if want.slabbedOnly {
            parameters = parameters.setting(.grading, to: SearchParameters.Grading.slabbed.rawValue)
        }

        return parameters.path(.Route.search)
    }

}