// OrbitalCamera.swift
// Blender-style orbit camera with pan, orbit, and dolly zoom.

import Observation
import simd

@Observable
final class OrbitalCamera {

    var azimuth: Float = Float.pi * 0.25
    var elevation: Float = Float.pi * 0.2
    var target: SIMD3<Float> = .zero
    var distance: Float = 7.0

    private let minDistance: Float = 0.5
    private let maxDistance: Float = 200.0
    private let minElevation: Float = -Float.pi * 0.49
    private let maxElevation: Float =  Float.pi * 0.49

    var eye: SIMD3<Float> {
        let x = distance * cosf(elevation) * sinf(azimuth)
        let y = distance * sinf(elevation)
        let z = distance * cosf(elevation) * cosf(azimuth)
        return target + SIMD3<Float>(x, y, z)
    }

    var viewMatrix: simd_float4x4 {
        MathUtils.lookAt(eye: eye, center: target, up: SIMD3<Float>(0, 1, 0))
    }

    func orbit(deltaX: Float, deltaY: Float) {
        azimuth -= deltaX * 0.008
        elevation += deltaY * 0.008
        elevation = min(max(elevation, minElevation), maxElevation)
    }

    func pan(deltaX: Float, deltaY: Float) {
        let right = SIMD3<Float>(cosf(azimuth), 0, -sinf(azimuth))
        let up = SIMD3<Float>(0, 1, 0)
        let speed: Float = distance * 0.002
        target += right * (-deltaX * speed) + up * (deltaY * speed)
    }

    func zoom(scale: Float) {
        distance /= scale
        distance = min(max(distance, minDistance), maxDistance)
    }

    func reset() {
        azimuth = Float.pi * 0.25
        elevation = Float.pi * 0.2
        distance = 7.0
        target = .zero
    }
}