//
//  ReaderView.swift
//  Zyquo Atlas
//
//  Author: Simon-Pierre Boucher
//  Mail: contact@spboucher.ai
//
//  Reader mode: a clean, themeable article view built from the tab's extracted
//  PageContext (Readability), with an optional AI summary at the top. Reader
//  typography (measure, size, spacing) follows the theme; honest fallback when
//  the page isn't an article.
//

import SwiftUI

struct ReaderView: View {
    @ObservedObject var tab: Tab
    @EnvironmentObject private var env: AppEnvironment
    @EnvironmentObject private var themeEngine: ThemeEngine
    private var theme: AtlasTheme { themeEngine.theme }

    @State private var context: PageContext?
    @State private var loadError: String?
    @StateObject private var ai = AIService()

    var body: some View {
        ScrollView {
            VStack(alignment: .leading, spacing: ZyquoSpacing.md) {
                if let ctx = context {
                    Text(ctx.title).font(.system(size: 30 * themeEngine.layout.uiScale, weight: .bold))
                        .foregroundStyle(theme.textPrimary)
                    if let byline = ctx.byline {
                        Text(byline).font(ZyquoFont.caption).foregroundStyle(theme.textSecondary)
                    }
                    summaryCard(ctx)
                    Divider().overlay(theme.border)
                    Text(ctx.markdown)
                        .font(.system(size: 17 * themeEngine.layout.uiScale))
                        .lineSpacing(8)
                        .foregroundStyle(theme.textPrimary)
                        .textSelection(.enabled)
                } else if let loadError {
                    Label(loadError, systemImage: "doc.plaintext")
                        .font(ZyquoFont.body()).foregroundStyle(theme.textSecondary)
                } else {
                    ProgressView().frame(maxWidth: .infinity).padding(ZyquoSpacing.xxl)
                }
            }
            .frame(maxWidth: 720, alignment: .leading)
            .frame(maxWidth: .infinity)
            .padding(.horizontal, ZyquoSpacing.xxl)
            .padding(.vertical, ZyquoSpacing.xl)
        }
        .background(theme.backgroundColor)
        .task(id: tab.id) { await load() }
    }

    private func summaryCard(_ ctx: PageContext) -> some View {
        VStack(alignment: .leading, spacing: ZyquoSpacing.xs) {
            HStack {
                Label("AI summary", systemImage: "sparkles").font(ZyquoFont.caption)
                    .foregroundStyle(theme.accentIndigo)
                Spacer()
                if !ai.isStreaming && ai.output.isEmpty {
                    Button("Summarize", action: { summarize(ctx) })
                        .font(ZyquoFont.caption).foregroundStyle(theme.accent)
                }
            }
            if !ai.output.isEmpty {
                Text(ai.output).font(ZyquoFont.body()).foregroundStyle(theme.textPrimary).textSelection(.enabled)
            } else if ai.isStreaming {
                Text("Summarizing…").font(ZyquoFont.caption).foregroundStyle(theme.textSecondary)
            }
        }
        .padding(ZyquoSpacing.md)
        .background(RoundedRectangle(cornerRadius: ZyquoRadius.medium).fill(theme.accentSubtle))
    }

    private func load() async {
        do { context = try await tab.extractPageContext() }
        catch { loadError = "Reader couldn't extract this page. It may be an app page or blocked." }
    }

    private func summarize(_ ctx: PageContext) {
        guard let model = env.model(for: .standard),
              let key = try? env.vault.apiKey(for: model.provider) else { return }
        ai.run(.summarize, on: ctx, model: model, apiKey: key)
    }
}