SwiftMail/Sources/SwiftIMAP/Models/MessageIdentifierSet.swift

// MessageIdentifierSet.swift
// Implementation of type-safe sets for IMAP message identifiers

import Foundation
import NIOIMAPCore

// MARK: - MessageIdentifier Protocol

/// Protocol for message identifiers (UID and SequenceNumber)
public protocol MessageIdentifier: Hashable, Comparable {
    var value: UInt32 { get }
    init(_ value: UInt32)
    static var latest: Self { get }
}

extension MessageIdentifier {
    public init(_ value: Int) {
        self.init(UInt32(value))
    }
    
    public static func < (lhs: Self, rhs: Self) -> Bool {
        return lhs.value < rhs.value
    }
}

// MARK: - UID Implementation

/// Represents a Unique Identifier (UID) in IMAP
public struct UID: MessageIdentifier, Sendable {
    public let value: UInt32
    
    public init(_ value: UInt32) {
        self.value = value
    }
    
    public static let latest = UID(UInt32.max)
    
    // Convert to NIO UID
    internal func toNIO() -> NIOIMAPCore.UID {
        return NIOIMAPCore.UID(rawValue: self.value)
    }
}

// MARK: - SequenceNumber Implementation

/// Represents a Sequence Number in IMAP
public struct SequenceNumber: MessageIdentifier {
    public let value: UInt32
    
    public init(_ value: UInt32) {
        self.value = value
    }
    
    public static let latest = SequenceNumber(UInt32.max)
    
    // Convert to NIO SequenceNumber
    internal func toNIO() -> NIOIMAPCore.SequenceNumber {
        return NIOIMAPCore.SequenceNumber(rawValue: self.value)
    }
}

// MARK: - MessageIdentifierSet Implementation

/// A type-safe set for message identifiers that provides an efficient
/// representation of non-contiguous ranges
public struct MessageIdentifierSet<Identifier: MessageIdentifier> {
    /// The underlying Foundation IndexSet that stores the actual data
    private var indexSet: Foundation.IndexSet
    
    /// Creates an empty set
    public init() {
        self.indexSet = Foundation.IndexSet()
    }
    
    /// Creates a set containing the given integer
    public init(_ value: Int) {
        self.indexSet = Foundation.IndexSet(integer: value)
    }
    
    /// Creates a set containing integers in the given range
    public init(_ range: ClosedRange<Int>) {
        self.indexSet = Foundation.IndexSet(integersIn: range)
    }
    
    /// Creates a set containing integers from a lower bound to the maximum value
    public init(_ range: PartialRangeFrom<Int>) {
        // Use Int.max as the upper bound for partial ranges
        self.indexSet = Foundation.IndexSet(integersIn: range.lowerBound...Int(UInt32.max))
    }
    
    /// Creates a set containing integers in the given ranges
    public init(ranges: ClosedRange<Int>...) {
        self.indexSet = Foundation.IndexSet()
        for range in ranges {
            self.indexSet.insert(integersIn: range)
        }
    }
    
    /// Creates a set from a comma-separated string like "1-3,5-10"
    public init?(string: String) {
        self.indexSet = Foundation.IndexSet()
        
        let components = string.components(separatedBy: ",")
        for component in components {
            let rangeParts = component.components(separatedBy: "-")
            if rangeParts.count == 1, let value = Int(rangeParts[0].trimmingCharacters(in: .whitespaces)) {
                // Single value
                self.indexSet.insert(value)
            } else if rangeParts.count == 2,
                      let lower = Int(rangeParts[0].trimmingCharacters(in: .whitespaces)),
                      let upper = Int(rangeParts[1].trimmingCharacters(in: .whitespaces)) {
                // Range
                self.indexSet.insert(integersIn: lower...upper)
            } else {
                return nil // Invalid format
            }
        }
    }
    
    /// Creates a set containing the given identifier
    public init(_ identifier: Identifier) {
        self.indexSet = Foundation.IndexSet(integer: Int(identifier.value))
    }
    
    /// Creates a set from an array of identifiers
    public init(_ identifiers: [Identifier]) {
        self.indexSet = Foundation.IndexSet()
        for identifier in identifiers {
            self.indexSet.insert(Int(identifier.value))
        }
    }
    
    /// Creates a set containing identifiers in the given range
    public init(_ range: ClosedRange<Identifier>) {
        self.indexSet = Foundation.IndexSet(integersIn: Int(range.lowerBound.value)...Int(range.upperBound.value))
    }
    
    /// Creates a set containing identifiers from a lower bound to the maximum value
    public init(_ range: PartialRangeFrom<Identifier>) {
        // Use the type's 'latest' value as the upper bound
        self.indexSet = Foundation.IndexSet(integersIn: Int(range.lowerBound.value)...Int(UInt32.max))
    }
    
    /// Inserts the given integer into the set
    public mutating func insert(_ value: Int) {
        indexSet.insert(value)
    }
    
    /// Inserts the given identifier into the set
    public mutating func insert(_ identifier: Identifier) {
        indexSet.insert(Int(identifier.value))
    }
    
    /// Inserts integers in the given range into the set
    public mutating func insert(range: ClosedRange<Int>) {
        indexSet.insert(integersIn: range)
    }
    
    /// Inserts integers from a lower bound to the maximum value
    public mutating func insert(range: PartialRangeFrom<Int>) {
        indexSet.insert(integersIn: range.lowerBound...Int.max)
    }
    
    /// Inserts identifiers in the given range into the set
    public mutating func insert(range: ClosedRange<Identifier>) {
        indexSet.insert(integersIn: Int(range.lowerBound.value)...Int(range.upperBound.value))
    }
    
    /// Inserts identifiers from a lower bound to the maximum value
    public mutating func insert(range: PartialRangeFrom<Identifier>) {
        indexSet.insert(integersIn: Int(range.lowerBound.value)...Int(UInt32.max))
    }
    
    /// Inserts integers in the given ranges into the set
    public mutating func insert(ranges: ClosedRange<Int>...) {
        for range in ranges {
            indexSet.insert(integersIn: range)
        }
    }
    
    /// Returns true if the set contains the given integer
    public func contains(_ value: Int) -> Bool {
        return indexSet.contains(value)
    }
    
    /// Returns true if the set contains the given identifier
    public func contains(_ identifier: Identifier) -> Bool {
        return indexSet.contains(Int(identifier.value))
    }
    
    /// Returns true if the set is empty
    public var isEmpty: Bool {
        return indexSet.isEmpty
    }
    
    /// Returns the number of integers in the set
    public var count: Int {
        return indexSet.count
    }
    
    /// Returns a view of the ranges in the set
    public var ranges: [ClosedRange<Int>] {
        return indexSet.rangeView.map { $0.lowerBound...$0.upperBound - 1 }
    }
    
    /// Converts the set to an array of identifiers
    public func toArray() -> [Identifier] {
        return indexSet.map { Identifier(UInt32($0)) }
    }
}

// MARK: - Type Aliases

/// A type-safe set of UIDs
public typealias UIDSet = MessageIdentifierSet<UID>

/// A type-safe set of sequence numbers
public typealias SequenceNumberSet = MessageIdentifierSet<SequenceNumber>

// MARK: - NIO Conversion Extensions

extension MessageIdentifierSet {
    /// Converts to NIO MessageIdentifierSetNonEmpty
    /// This method uses type constraints to determine the correct NIO type
    internal func toNIOSet<NIOType>() -> NIOIMAPCore.MessageIdentifierSetNonEmpty<NIOType> {
		
		precondition(!self.isEmpty, "Cannot convert an empty set to NIO")
		
        // Create an empty NIO set
        var nioSet = NIOIMAPCore.MessageIdentifierSet<NIOType>()
        
        // Convert each range to a NIO range and add it to the set
        for range in self.ranges {
            if Identifier.self == UID.self && NIOType.self == NIOIMAPCore.UID.self {
                let startUID = NIOIMAPCore.UID(rawValue: UInt32(range.lowerBound))
                let endUID = NIOIMAPCore.UID(rawValue: UInt32(range.upperBound))
                let nioRange = NIOIMAPCore.MessageIdentifierRange(startUID...endUID)
                nioSet.formUnion(NIOIMAPCore.MessageIdentifierSet<NIOType>(nioRange as! NIOIMAPCore.MessageIdentifierRange<NIOType>))
            } else if Identifier.self == SequenceNumber.self && NIOType.self == NIOIMAPCore.SequenceNumber.self {
                let startSeq = NIOIMAPCore.SequenceNumber(rawValue: UInt32(range.lowerBound))
                let endSeq = NIOIMAPCore.SequenceNumber(rawValue: UInt32(range.upperBound))
                let nioRange = NIOIMAPCore.MessageIdentifierRange(startSeq...endSeq)
                nioSet.formUnion(NIOIMAPCore.MessageIdentifierSet<NIOType>(nioRange as! NIOIMAPCore.MessageIdentifierRange<NIOType>))
            } else {
				preconditionFailure("Unsupported type combination")
            }
        }
        
        return NIOIMAPCore.MessageIdentifierSetNonEmpty(set: nioSet)!
    }
}

extension MessageIdentifierSet where Identifier == UID {
    /// Converts to NIO MessageIdentifierSetNonEmpty for UID
    internal func toNIOSet() -> NIOIMAPCore.MessageIdentifierSetNonEmpty<NIOIMAPCore.UID>? {
        if self.isEmpty {
            return nil
        }
        
        var nioSet = NIOIMAPCore.MessageIdentifierSet<NIOIMAPCore.UID>()
        
        for range in self.ranges {
            let startUID = NIOIMAPCore.UID(rawValue: UInt32(range.lowerBound))
            let endUID = NIOIMAPCore.UID(rawValue: UInt32(range.upperBound))
            let nioRange = NIOIMAPCore.MessageIdentifierRange(startUID...endUID)
            nioSet.formUnion(NIOIMAPCore.MessageIdentifierSet<NIOIMAPCore.UID>(nioRange))
        }
        
        return NIOIMAPCore.MessageIdentifierSetNonEmpty(set: nioSet)
    }
}

extension MessageIdentifierSet where Identifier == SequenceNumber {
    /// Converts to NIO MessageIdentifierSetNonEmpty for SequenceNumber
    internal func toNIOSet() -> NIOIMAPCore.MessageIdentifierSetNonEmpty<NIOIMAPCore.SequenceNumber>? {
        if self.isEmpty {
            return nil
        }
        
        var nioSet = NIOIMAPCore.MessageIdentifierSet<NIOIMAPCore.SequenceNumber>()
        
        for range in self.ranges {
            let startSeq = NIOIMAPCore.SequenceNumber(rawValue: UInt32(range.lowerBound))
            let endSeq = NIOIMAPCore.SequenceNumber(rawValue: UInt32(range.upperBound))
            let nioRange = NIOIMAPCore.MessageIdentifierRange(startSeq...endSeq)
            nioSet.formUnion(NIOIMAPCore.MessageIdentifierSet<NIOIMAPCore.SequenceNumber>(nioRange))
        }
        
        return NIOIMAPCore.MessageIdentifierSetNonEmpty(set: nioSet)
    }
}

// MARK: - Conversion from NIO types

extension UID {
    /// Create a UID from a NIO UID
    public init(nio: NIOIMAPCore.UID) {
        self.init(nio.rawValue)
    }
}

extension SequenceNumber {
    /// Create a SequenceNumber from a NIO SequenceNumber
    public init(nio: NIOIMAPCore.SequenceNumber) {
        self.init(nio.rawValue)
    }
}

// MARK: - Example Usage

/*
// Create a set with a single UID
var uidSet = UIDSet(UID(1))

// Create a set with a range of UIDs
let rangeSet = UIDSet(UID(1)...UID(10))

// Create a set with multiple ranges
let multiRangeSet = UIDSet(ranges: 1...3, 5...10)

// Create a set from a string
if let setFromString = UIDSet(string: "1-3,5-10") {
    // Use the set
}

// Add a UID to the set
uidSet.insert(UID(4))

// Add a range of UIDs
uidSet.insert(range: UID(5)...UID(10))

// Convert to NIO MessageIdentifierSetNonEmpty for use with the IMAP library
if let nioSet = uidSet.toNIOSet() {
    // Use with NIO IMAP library
}
*/