import SwiftUI

struct HexView: View {
    let data: Data

    @State private var showAll = false

    private var displayData: Data {
        if showAll || data.count <= 1024 {
            return data
        }
        return data.prefix(1024)
    }

    var body: some View {
        VStack(alignment: .leading, spacing: 0) {
            // Header
            Text("Offset    00 01 02 03 04 05 06 07  08 09 0A 0B 0C 0D 0E 0F  ASCII")
                .font(.system(.caption2, design: .monospaced))
                .foregroundStyle(.secondary)
                .padding(.bottom, 4)

            // Hex rows
            let bytes = [UInt8](displayData)
            let rowCount = (bytes.count + 15) / 16

            ForEach(0..<rowCount, id: \.self) { row in
                hexRow(bytes: bytes, row: row)
            }

            // Show more
            if !showAll && data.count > 1024 {
                Button {
                    showAll = true
                } label: {
                    Text("Show All (\(formatBytes(data.count)) total)")
                        .font(.system(.caption, design: .monospaced))
                }
                .padding(.top, 8)
            }
        }
        .textSelection(.enabled)
    }

    private func hexRow(bytes: [UInt8], row: Int) -> some View {
        let offset = row * 16
        let end = min(offset + 16, bytes.count)
        let rowBytes = Array(bytes[offset..<end])

        return HStack(spacing: 0) {
            // Offset
            Text(String(format: "%08X  ", offset))
                .foregroundStyle(.secondary)

            // Hex bytes
            Text(hexString(rowBytes))

            // ASCII
            Text(" ")
            Text(asciiString(rowBytes))
                .foregroundStyle(.orange)
        }
        .font(.system(.caption2, design: .monospaced))
    }

    private func hexString(_ bytes: [UInt8]) -> String {
        var result = ""
        for i in 0..<16 {
            if i < bytes.count {
                result += String(format: "%02X ", bytes[i])
            } else {
                result += "   "
            }
            if i == 7 {
                result += " "
            }
        }
        return result
    }

    private func asciiString(_ bytes: [UInt8]) -> String {
        var result = ""
        for byte in bytes {
            if byte >= 0x20, byte <= 0x7E {
                result += String(UnicodeScalar(byte))
            } else {
                result += "."
            }
        }
        return result
    }

    private func formatBytes(_ count: Int) -> String {
        if count < 1024 { return "\(count) B" }
        if count < 1_048_576 { return String(format: "%.1f KB", Double(count) / 1024) }
        return String(format: "%.1f MB", Double(count) / 1_048_576)
    }
}