//
//  ExportService.swift
//  Zyquo Local
//
//  Author: Simon-Pierre Boucher
//  Mail: contact@spboucher.ai
//

import AppKit
import Foundation
import UniformTypeIdentifiers

/// Conversation export: Markdown and PDF via save panels.
@MainActor
enum ExportService {
    static func markdown(for conversation: Conversation) -> String {
        var lines: [String] = []
        lines.append("# \(conversation.title)")
        lines.append("")
        lines.append("_Exported from Zyquo Local · \(conversation.updatedAt.formatted(date: .abbreviated, time: .shortened))_")
        if let modelID = conversation.modelID {
            lines.append("_Model: \(modelID)_")
        }
        lines.append("")
        if let system = conversation.systemPrompt, !system.isEmpty {
            lines.append("> **System:** \(system)")
            lines.append("")
        }
        for message in conversation.messages where message.role != .system {
            lines.append(message.role == .user ? "## You" : "## Assistant")
            lines.append("")
            if let thinking = message.thinking, !thinking.isEmpty {
                lines.append("<details><summary>Thinking</summary>")
                lines.append("")
                lines.append(thinking)
                lines.append("")
                lines.append("</details>")
                lines.append("")
            }
            lines.append(message.content)
            if let stats = message.stats {
                lines.append("")
                lines.append(String(
                    format: "_%.1f tok/s · %d tokens · %.1fs to first token_",
                    stats.tokensPerSecond, stats.generationTokenCount, stats.timeToFirstToken))
            }
            lines.append("")
        }
        return lines.joined(separator: "\n")
    }

    static func exportMarkdown(_ conversation: Conversation) {
        let panel = NSSavePanel()
        panel.allowedContentTypes = [.init(filenameExtension: "md") ?? .plainText]
        panel.nameFieldStringValue = sanitizedFileName(conversation.title) + ".md"
        guard panel.runModal() == .OK, let url = panel.url else { return }
        try? markdown(for: conversation).write(to: url, atomically: true, encoding: .utf8)
    }

    static func exportPDF(_ conversation: Conversation) {
        let panel = NSSavePanel()
        panel.allowedContentTypes = [.pdf]
        panel.nameFieldStringValue = sanitizedFileName(conversation.title) + ".pdf"
        guard panel.runModal() == .OK, let url = panel.url else { return }
        writePDF(conversation, to: url)
    }

    /// Simple paginated PDF from an attributed rendition of the transcript.
    private static func writePDF(_ conversation: Conversation, to url: URL) {
        let pageRect = CGRect(x: 0, y: 0, width: 612, height: 792)  // US Letter
        let inset: CGFloat = 54
        let contentRect = pageRect.insetBy(dx: inset, dy: inset)

        let text = NSMutableAttributedString()
        let titleFont = NSFont.systemFont(ofSize: 18, weight: .semibold)
        let bodyFont = NSFont.systemFont(ofSize: 11)
        let roleFont = NSFont.systemFont(ofSize: 11, weight: .semibold)
        let metaFont = NSFont.systemFont(ofSize: 9)

        text.append(NSAttributedString(
            string: conversation.title + "\n",
            attributes: [.font: titleFont]))
        text.append(NSAttributedString(
            string: "Exported from Zyquo Local · \(conversation.updatedAt.formatted())\n\n",
            attributes: [.font: metaFont, .foregroundColor: NSColor.secondaryLabelColor]))

        for message in conversation.messages where message.role != .system {
            text.append(NSAttributedString(
                string: (message.role == .user ? "You" : "Assistant") + "\n",
                attributes: [.font: roleFont]))
            text.append(NSAttributedString(
                string: message.content + "\n\n",
                attributes: [.font: bodyFont]))
        }

        var mediaBox = pageRect
        guard let consumer = CGDataConsumer(url: url as CFURL),
            let context = CGContext(consumer: consumer, mediaBox: &mediaBox, nil)
        else { return }

        let framesetter = CTFramesetterCreateWithAttributedString(text)
        var location = 0
        while location < text.length {
            context.beginPDFPage(nil)
            let path = CGPath(rect: contentRect, transform: nil)
            let frame = CTFramesetterCreateFrame(
                framesetter, CFRange(location: location, length: 0), path, nil)
            CTFrameDraw(frame, context)
            let visible = CTFrameGetVisibleStringRange(frame)
            location += max(visible.length, 1)
            context.endPDFPage()
        }
        context.closePDF()
    }

    private static func sanitizedFileName(_ name: String) -> String {
        let invalid = CharacterSet(charactersIn: "/\\:?%*|\"<>")
        let cleaned = name.components(separatedBy: invalid).joined(separator: "-")
        return cleaned.isEmpty ? "Conversation" : cleaned
    }
}