//
//  InstanceFeatures.swift
//  Tusker
//
//  Created by Shadowfacts on 1/23/22.
//  Copyright © 2022 Shadowfacts. All rights reserved.
//

import Foundation
import Combine
import Pachyderm

public class InstanceFeatures: ObservableObject {
    private static let pleromaVersionRegex = try! NSRegularExpression(pattern: "\\(compatible; pleroma (.*)\\)", options: .caseInsensitive)
    private static let akkomaVersionRegex = try! NSRegularExpression(pattern: "\\(compatible; akkoma (.*)\\)", options: .caseInsensitive)
    
    private let _featuresUpdated = PassthroughSubject<Void, Never>()
    public var featuresUpdated: some Publisher<Void, Never> { _featuresUpdated }
    
    @Published private var instanceType: InstanceType = .mastodon(.vanilla, nil)
    @Published public private(set) var maxStatusChars = 500
    @Published public private(set) var charsReservedPerURL = 23
    @Published public private(set) var maxPollOptionChars: Int?
    @Published public private(set) var maxPollOptionsCount: Int?
    
    public var localOnlyPosts: Bool {
        switch instanceType {
        case .mastodon(.hometown(_), _), .mastodon(.glitch, _):
            return true
        default:
            return false
        }
    }
    
    public var mastodonAttachmentRestrictions: Bool {
        instanceType.isMastodon
    }
    
    public var pollsAndAttachments: Bool {
        instanceType.isPleroma
    }
    
    public var boostToOriginalAudience: Bool {
        instanceType.isPleroma || instanceType.isMastodon
    }
    
    public var profilePinnedStatuses: Bool {
        switch instanceType {
        case .pixelfed:
            return false
        default:
            return true
        }
    }
    
    public var trends: Bool {
        instanceType.isMastodon
    }
    
    public var profileSuggestions: Bool {
        instanceType.isMastodon && hasMastodonVersion(3, 4, 0)
    }
    
    public var trendingStatusesAndLinks: Bool {
        instanceType.isMastodon && hasMastodonVersion(3, 5, 0)
    }
    
    public var reblogVisibility: Bool {
        (instanceType.isMastodon && hasMastodonVersion(2, 8, 0))
            || (instanceType.isPleroma && hasPleromaVersion(2, 0, 0))
    }
    
    public var probablySupportsMarkdown: Bool {
        switch instanceType {
        case .pleroma(_), .mastodon(.glitch, _), .mastodon(.hometown(_), _):
            return true
        default:
            return false
        }
    }
    
    public var needsLocalOnlyEmojiHack: Bool {
        if case .mastodon(.glitch, _) = instanceType {
            return true
        } else {
            return false
        }
    }
    
    public var needsWideColorGamutHack: Bool {
        if case .mastodon(_, .some(let version)) = instanceType {
            return version < Version(4, 0, 0)
        } else {
            return true
        }
    }
    
    public var canFollowHashtags: Bool {
        hasMastodonVersion(4, 0, 0)
    }
    
    public var filtersV2: Bool {
        hasMastodonVersion(4, 0, 0)
    }
    
    public var notificationsAllowedTypes: Bool {
        hasMastodonVersion(3, 5, 0)
    }
    
    public var pollVotersCount: Bool {
        instanceType.isMastodon
    }
    
    public init() {
    }
    
    public func update(instance: Instance, nodeInfo: NodeInfo?) {
        let ver = instance.version.lowercased()
        if ver.contains("glitch") {
            instanceType = .mastodon(.glitch, Version(string: ver))
        } else if nodeInfo?.software.name == "hometown" {
            var mastoVersion: Version?
            var hometownVersion: Version?
            let parts = ver.split(separator: "+")
            if parts.count == 2,
               let first = Version(string: String(parts[0])) {
                if first > Version(1, 0, 8) {
                    // like 3.5.5+hometown-1.0.9
                    mastoVersion = first
                    if parts[1].starts(with: "hometown-") {
                        hometownVersion = Version(string: String(parts[1][parts[1].index(parts[1].startIndex, offsetBy: "hometown-".count + 1)...]))
                    }
                } else {
                    // like "1.0.6+3.5.2"
                    hometownVersion = first
                    mastoVersion = Version(string: String(parts[1]))
                }
            } else {
                mastoVersion = Version(string: ver)
            }
            instanceType = .mastodon(.hometown(hometownVersion), mastoVersion)
        } else if ver.contains("pleroma") {
            var pleromaVersion: Version?
            if let match = InstanceFeatures.pleromaVersionRegex.firstMatch(in: ver, range: NSRange(location: 0, length: ver.utf16.count)) {
                pleromaVersion = Version(string: (ver as NSString).substring(with: match.range(at: 1)))
            }
            instanceType = .pleroma(.vanilla(pleromaVersion))
        } else if ver.contains("akkoma") {
            var akkomaVersion: Version?
            if let match = InstanceFeatures.akkomaVersionRegex.firstMatch(in: ver, range: NSRange(location: 0, length: ver.utf16.count)) {
                akkomaVersion = Version(string: (ver as NSString).substring(with: match.range(at: 1)))
            }
            instanceType = .pleroma(.akkoma(akkomaVersion))
        } else if ver.contains("pixelfed") {
            instanceType = .pixelfed
        } else {
            instanceType = .mastodon(.vanilla, Version(string: ver))
        }
        
        maxStatusChars = instance.maxStatusCharacters ?? 500
        charsReservedPerURL = instance.configuration?.statuses.charactersReservedPerURL ?? 23 // default Mastodon link length
        if let pollsConfig = instance.pollsConfiguration {
            maxPollOptionChars = pollsConfig.maxCharactersPerOption
            maxPollOptionsCount = pollsConfig.maxOptions
        }
        
        _featuresUpdated.send()
    }
    
    public func hasMastodonVersion(_ major: Int, _ minor: Int, _ patch: Int) -> Bool {
        if case .mastodon(_, .some(let version)) = instanceType {
            return version >= Version(major, minor, patch)
        } else {
            return false
        }
    }
    
    func hasPleromaVersion(_ major: Int, _ minor: Int, _ patch: Int) -> Bool {
        switch instanceType {
        case .pleroma(.vanilla(.some(let version))), .pleroma(.akkoma(.some(let version))):
            return version >= Version(major, minor, patch)
        default:
            return false
        }
    }
}

extension InstanceFeatures {
    enum InstanceType {
        case mastodon(MastodonType, Version?)
        case pleroma(PleromaType)
        case pixelfed
        
        var isMastodon: Bool {
            if case .mastodon(_, _) = self {
                return true
            } else {
                return false
            }
        }
        
        var isPleroma: Bool {
            if case .pleroma(_) = self {
                return true
            } else {
                return false
            }
        }
    }
    
    enum MastodonType {
        case vanilla
        case hometown(Version?)
        case glitch
    }
    
    enum PleromaType {
        case vanilla(Version?)
        case akkoma(Version?)
    }
}

extension InstanceFeatures {
    struct Version: Equatable, Comparable {
        private static let regex = try! NSRegularExpression(pattern: "^(\\d+)\\.(\\d+)\\.(\\d+).*$")
        
        let major: Int
        let minor: Int
        let patch: Int
        
        init(_ major: Int, _ minor: Int, _ patch: Int) {
            self.major = major
            self.minor = minor
            self.patch = patch
        }
        
        init?(string: String) {
            guard let match = Version.regex.firstMatch(in: string, range: NSRange(location: 0, length: string.utf16.count)),
                  match.numberOfRanges == 4 else {
                return nil
            }
            let majorStr = (string as NSString).substring(with: match.range(at: 1))
            let minorStr = (string as NSString).substring(with: match.range(at: 2))
            let patchStr = (string as NSString).substring(with: match.range(at: 3))
            guard let major = Int(majorStr),
                  let minor = Int(minorStr),
                  let patch = Int(patchStr) else {
                return nil
            }
            self.major = major
            self.minor = minor
            self.patch = patch
        }
        
        static func ==(lhs: Version, rhs: Version) -> Bool {
            return lhs.major == rhs.major && lhs.minor == rhs.minor && lhs.patch == rhs.patch
        }
        
        static func < (lhs: InstanceFeatures.Version, rhs: InstanceFeatures.Version) -> Bool {
            if lhs.major < rhs.major {
                return true
            } else if lhs.major > rhs.major {
                return false
            } else if lhs.minor < rhs.minor {
                return true
            } else if lhs.minor > rhs.minor {
                return false
            } else if lhs.patch < rhs.patch {
                return true
            } else {
                return false
            }
        }
    }
}