//
//  PlotView.swift
//  Metrika
//
//  Author:  Simon-Pierre Boucher
//  Contact: contact@spboucher.ai
//  Copyright © 2026 Simon-Pierre Boucher. All rights reserved.
//

import Charts
import SwiftUI
import ZQGraphics

/// Swift Charts rendering of the session's latest plot spec. The custom
/// Metal renderer takes over past ~1M points (v0.3, CLAUDE.md §7).
struct PlotView: View {
    @Environment(SessionModel.self) private var model

    /// Past this many points, Swift Charts degrades — the Metal renderer
    /// takes over (overridable for tests via METRIKA_METAL_THRESHOLD).
    private static let metalThreshold: Int = {
        if let text = ProcessInfo.processInfo.environment["METRIKA_METAL_THRESHOLD"],
           let value = Int(text) {
            return value
        }
        return 100_000
    }()

    var body: some View {
        if let plot = model.lastPlot,
           plot.kind == .scatter,
           plot.series.reduce(0, { $0 + $1.x.count }) > Self.metalThreshold {
            MetalScatterPane(plot: plot)
                .accessibilityLabel("Metal scatter renderer")
        } else if let plot = model.lastPlot {
            Chart {
                ForEach(Array(plot.series.enumerated()), id: \.offset) { _, series in
                    ForEach(series.x.indices, id: \.self) { index in
                        switch plot.kind {
                        case .scatter:
                            PointMark(
                                x: .value(plot.xLabel, series.x[index]),
                                y: .value(plot.yLabel, series.y[index])
                            )
                            .symbolSize(20)
                            .foregroundStyle(by: .value("Series", series.label))
                        case .line, .kdensity:
                            LineMark(
                                x: .value(plot.xLabel, series.x[index]),
                                y: .value(plot.yLabel, series.y[index])
                            )
                            .foregroundStyle(by: .value("Series", series.label))
                        case .histogram:
                            BarMark(
                                x: .value(plot.xLabel, series.x[index]),
                                y: .value(plot.yLabel, series.y[index])
                            )
                            .foregroundStyle(by: .value("Series", series.label))
                        }
                    }
                }
            }
            .chartXAxisLabel(plot.xLabel)
            .chartYAxisLabel(plot.yLabel)
            .padding(12)
        } else {
            ContentUnavailableView(
                "No plot", systemImage: "chart.xyaxis.line",
                description: Text("Run a graph command to see it here.")
            )
        }
    }
}