// 
// Copyright 2023, 2024 New Vector Ltd.
//
// SPDX-License-Identifier: AGPL-3.0-only
// Please see LICENSE in the repository root for full details.
//

import Foundation

@available(iOS 15.0, *)
private enum PillAttachmentKind {
    case attachment(PillTextAttachment)
    case string(NSAttributedString)
}

@available(iOS 15.0, *)
struct PillProvider {
    private let session: MXSession
    private let eventFormatter: MXKEventFormatter
    private let event: MXEvent?
    private let roomState: MXRoomState
    private let latestRoomState: MXRoomState?
    private let isEditMode: Bool
    
    init(withSession session: MXSession,
         eventFormatter: MXKEventFormatter,
         event: MXEvent?,
         roomState: MXRoomState,
         andLatestRoomState latestRoomState: MXRoomState?,
         isEditMode: Bool) {
    
        self.session = session
        self.eventFormatter = eventFormatter
        self.event = event
        self.roomState = roomState
        self.latestRoomState = latestRoomState
        self.isEditMode = isEditMode
    }
    
    func pillTextAttachmentString(forUrl url: URL, withLabel label: String) -> NSAttributedString? {
        
        // Try to get a pill from this url
        guard let pillType = PillType.from(url: url) else {
            return nil
        }
                
        // Do not pillify an url if it is a markdown or an http link (except for user and room) with a custom text
        
        // First, we need to handle the case where the label can contains more than one # (room alias)
        var urlFromLabel: URL?
        /*
        BWI: 6393 fix permalink to message not displayed as pill.
         Due to changes in the latest iOS version, we need to remove the percent encoding from the label before searching for markdown or an http link.
        The URL extracted from an attributed string now returns a URL without percent encoding. Checking against the encoded label will always fail.
         */
        if #available(iOS 18.0, *) {
            urlFromLabel = URL(string: label.removingPercentEncoding ?? label)?.absoluteURL
        } else {
            urlFromLabel = URL(string: label)?.absoluteURL
        }
        if urlFromLabel == nil, label.filter({ $0 == "#" }).count > 1 {
            if let escapedLabel = label.addingPercentEncoding(withAllowedCharacters: .urlQueryAllowed), let url = URL(string: escapedLabel) {
                urlFromLabel = Tools.fixURL(withSeveralHashKeys: url)
            }
        }
        
        let fixedUrl = Tools.fixURL(withSeveralHashKeys: url)
        let isUrlMarkDownLink = urlFromLabel != fixedUrl

        let result: PillAttachmentKind
        switch pillType {
        case .user(let userId):
            var userFound = false
            result = pillTextAttachment(forUserId: userId, userFound: &userFound)
            // if it is a markdown link and we didn't found the user, don't pillify it
            if isUrlMarkDownLink && !userFound {
                return nil
            }
        case .room(let roomId):
            var roomFound = false
            result = pillTextAttachment(forRoomId: roomId, roomFound: &roomFound)
            // if it is a markdown link and we didn't found the room, don't pillify it
            if isUrlMarkDownLink && !roomFound {
                return nil
            }
        case .message(let roomId, let messageId):
            // if it is a markdown link, don't pillify it
            if isUrlMarkDownLink {
                return nil
            }
            result = pillTextAttachment(forMessageId: messageId, inRoomId: roomId)
        }
        
        switch result {
        case .attachment(let pillTextAttachment):
            return PillsFormatter.attributedStringWithAttachment(pillTextAttachment, link: isEditMode ? nil : url, font: eventFormatter.defaultTextFont)
        case .string(let attributedString):
            // if we don't have an attachment, use the fallback attributed string
            let newAttrString = NSMutableAttributedString(attributedString: attributedString)
            if let font = eventFormatter.defaultTextFont {
                newAttrString.addAttribute(.font, value: font, range: .init(location: 0, length: newAttrString.length))
            }
            newAttrString.addAttribute(.foregroundColor, value: ThemeService.shared().theme.colors.links, range: .init(location: 0, length: newAttrString.length))
            newAttrString.addAttribute(.link, value: url, range: .init(location: 0, length: newAttrString.length))
            return newAttrString
        }
    }
    
    /// Retrieve the latest available `MXRoomMember` from given data.
    ///
    /// - Parameters:
    ///   - userId: the id of the user
    /// - Returns: the room member, if available
    private func roomMember(withUserId userId: String) -> MXRoomMember? {
        return latestRoomState?.members.member(withUserId: userId) ?? roomState.members.member(withUserId: userId)
    }
    
    /// Create a pill representation for a given user
    /// - Parameters:
    ///   - userId: the user MatrixID
    ///   - userFound: this flag will be set to true if a user is found locally with this userId
    /// - Returns: a pill attachment
    private func pillTextAttachment(forUserId userId: String, userFound: inout Bool) -> PillAttachmentKind {
        // Search for a room member matching this user id
        let roomMember = self.roomMember(withUserId: userId)
        var user: MXUser?
        
        if roomMember == nil {
            // fallback on getting the user from the session's store
            user = session.user(withUserId: userId)
        }

        
        let avatarUrl = roomMember?.avatarUrl ?? user?.avatarUrl
        let displayName = roomMember?.displayname ?? user?.displayName ?? userId
        let isHighlighted = userId == session.myUserId
            // No actual event means it is a composer Pill. No highlight
            && event != nil
            // No highlight on self-mentions
            && event?.sender != session.myUserId

        let avatar: PillTextAttachmentItem
        if roomMember == nil && user == nil {
            avatar = .asset(named: "pill_user",
                            parameters: .init(tintColor: PillAssetColor(uiColor: ThemeService.shared().theme.colors.secondaryContent),
                                              rawRenderingMode: UIImage.RenderingMode.alwaysOriginal.rawValue,
                                              padding: 0.0))
        } else {
            avatar = .avatar(url: avatarUrl,
                             string: displayName,
                             matrixId: userId)
        }

        let data = PillTextAttachmentData(pillType: .user(userId: userId),
                                          items: [
                                            avatar,
                                            .text(displayName)
                                          ],
                                          isHighlighted: isHighlighted,
                                          alpha: 1.0,
                                          font: eventFormatter.defaultTextFont)
        
        userFound = roomMember != nil || user != nil
        
        if let attachment = PillTextAttachment(attachmentData: data) {
            return .attachment(attachment)
        }
        
        return .string(NSMutableAttributedString(string: displayName))
    }
    
    /// Create a pill representation for a given room
    /// - Parameters:
    ///   - roomId: the room MXID or alias
    ///   - roomFound: this flag will be set to true if a room is found locally with this roomId
    /// - Returns: a pill attachment
    private func pillTextAttachment(forRoomId roomId: String, roomFound: inout Bool) -> PillAttachmentKind {
        // Get the room matching this roomId
        let room = roomId.starts(with: "#") ? session.room(withAlias: roomId) : session.room(withRoomId: roomId)
        let displayName = room?.displayName ?? VectorL10n.pillRoomFallbackDisplayName
        
        let avatar: PillTextAttachmentItem
        if let room {
            if session.spaceService.getSpace(withId: roomId) != nil {
                avatar = .spaceAvatar(url: room.avatarData.mxContentUri,
                                      string: displayName,
                                      matrixId: roomId)
            } else {
                avatar = .avatar(url: room.avatarData.mxContentUri,
                                 string: displayName,
                                 matrixId: roomId)
            }
        } else {
            avatar = .asset(named: "link_icon",
                            parameters: .init(backgroundColor: PillAssetColor(uiColor: ThemeService.shared().theme.colors.links),
                                              rawRenderingMode: UIImage.RenderingMode.alwaysTemplate.rawValue))
        }
        
        let data = PillTextAttachmentData(pillType: .room(roomId: roomId),
                                          items: [
                                            avatar,
                                            .text(displayName)
                                          ],
                                          isHighlighted: false,
                                          alpha: 1.0,
                                          font: eventFormatter.defaultTextFont)
        
        roomFound = room != nil
        
        if let attachment = PillTextAttachment(attachmentData: data) {
            return .attachment(attachment)
        }
        
        return .string(NSMutableAttributedString(string: displayName))
    }
        
    /// Create a pill representation for a message in a room
    /// - Parameters:
    ///   - messageId: message eventId
    ///   - roomId: roomId of the message
    /// - Returns: a pill attachment
    private func pillTextAttachment(forMessageId messageId: String, inRoomId roomId: String) -> PillAttachmentKind {
        
        // Check if this is the current room
        if roomId == roomState.roomId {
            return pillTextAttachment(inCurrentRoomForMessageId: messageId)
        }

        let room = session.room(withRoomId: roomId)

        let avatar: PillTextAttachmentItem
        if let room {
            avatar = .avatar(url: room.avatarData.mxContentUri,
                             string: room.displayName,
                             matrixId: roomId)
        } else {
            avatar = .asset(named: "link_icon",
                            parameters: .init(backgroundColor: PillAssetColor(uiColor: ThemeService.shared().theme.colors.links),
                                              rawRenderingMode: UIImage.RenderingMode.alwaysTemplate.rawValue))
                                              
        }
        
        let displayText = room?.displayName.flatMap { VectorL10n.pillMessageIn($0) } ?? VectorL10n.pillMessage

        let data = PillTextAttachmentData(pillType: .message(roomId: roomId, eventId: messageId),
                                          items: [
                                            avatar,
                                            .text(displayText)
                                          ],
                                          isHighlighted: false,
                                          alpha: 1.0,
                                          font: eventFormatter.defaultTextFont)
        
        if let attachment = PillTextAttachment(attachmentData: data) {
            return .attachment(attachment)
        }
        
        return .string(NSMutableAttributedString(string: displayText))
    }
    
    /// Create a pill representation for a message in the current room
    /// - Parameters:
    ///   - messageId: message eventId
    /// - Returns: a pill attachment
    private func pillTextAttachment(inCurrentRoomForMessageId messageId: String) -> PillAttachmentKind {
        var roomMember: MXRoomMember?
        // If we have the event locally, try to get the room member
        if let event = session.store.event(withEventId: messageId, inRoom: roomState.roomId) {
            roomMember = self.roomMember(withUserId: event.sender)
        }

        let displayText: String
        let avatar: PillTextAttachmentItem
        if let roomMember {
            displayText = VectorL10n.pillMessageFrom(roomMember.displayname ?? roomMember.userId)
            avatar = .avatar(url: roomMember.avatarUrl,
                             string: roomMember.displayname,
                             matrixId: roomMember.userId)
        } else {
            displayText = VectorL10n.pillMessage
            avatar = .asset(named: "link_icon",
                            parameters: .init(backgroundColor: PillAssetColor(uiColor: ThemeService.shared().theme.colors.links),
                                              rawRenderingMode: UIImage.RenderingMode.alwaysTemplate.rawValue))
        }

        let data = PillTextAttachmentData(pillType: .message(roomId: roomState.roomId, eventId: messageId),
                                          items: [
                                            avatar,
                                            .text(displayText)
                                          ].compactMap { $0 },
                                          isHighlighted: false,
                                          alpha: 1.0,
                                          font: eventFormatter.defaultTextFont)

        if let attachment = PillTextAttachment(attachmentData: data) {
            return .attachment(attachment)
        }

        return .string(NSMutableAttributedString(string: displayText))
    }
}