/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at https://mozilla.org/MPL/2.0/. */

using System.Linq;
using CultMath;
using static CultMath.math;

// Cut 1 (docs/fire-control-cut.md): geometry -- whether a weapon bears on a point is decided here and
// nowhere else -- no prefab, transform, ArticulationPoint or renderer may influence it (R6, R7). Mount
// direction and arc are both derived per read from catalog data and the item's authored rotation; neither
// is ever stored on the entity.
// Cut 2 adds the reveal rule (R5) and the resolved targeting-system stats an entity fires with, both
// likewise derived on every read and never cached.
public static class FireControl
{
    // The planar unit vector a hardpoint's weapon points along, derived solely from the item's authored
    // rotation (R6, the same convention reaction thrusters already use) -- never from a live Unity
    // transform. This is the item-rotation path Behavior.Direction now uses unconditionally, after the
    // HardpointTransforms readback branch is deleted.
    public static float3 MountDirection(EquippedItem item)
    {
        var itemDirection = item.Entity.Direction.Rotate(item.EquippableItem.Rotation);
        return normalize(float3(itemDirection.x, 0, itemDirection.y));
    }

    // Full arc width in degrees: the per-hardpoint override when authored (nonzero), else
    // GameplaySettings.FiringArc. Zero on the hardpoint means "use the default," not "no arc."
    public static float ArcFor(EquippedItem item)
    {
        var hardpoint = item.Entity.Hardpoints[item.Position.x, item.Position.y];
        var arc = hardpoint?.FiringArc ?? 0f;
        return arc > 0 ? arc : item.ItemManager.GameplaySettings.FiringArc;
    }

    // Planar bearing test (R7: the simulation is 2D, the 3D is set dressing -- target height never enters
    // this). An arc of 360 degrees or more passes unconditionally, which is how a turret hardpoint
    // (authored FiringArc: 360, Q1) tracks all the way around without a second type.
    public static bool InArc(EquippedItem weapon, float3 toTarget)
    {
        var arc = ArcFor(weapon);
        if (arc >= 360f) return true;
        var planarTarget = normalize(float3(toTarget.x, 0, toTarget.z));
        return dot(MountDirection(weapon), planarTarget) >= cos(radians(arc / 2f));
    }

    // Cut 2, R5: whether `observer` has resolved `item` (which must belong to some entity in the zone) well
    // enough to aim at it. Derived fresh from EntityInfoGathered on every call -- nothing caches a reveal
    // result, so decay drops it the moment info falls back below tier, with no clearing loop anywhere.
    //
    // Ranking: the target's own non-hull equipment, hardpoint-mounted gear first (the big obvious things),
    // then by size descending, ties broken by equipment order (OrderByDescending is a stable sort, so this
    // needs no explicit tie-break key). Item i of N reveals once info crosses
    // lerp(TargetArmorInfoThreshold, TargetGearInfoThreshold, i / max(1, N - 1)) -- the first item to reveal
    // does so at the armor tier, the last at the gear tier.
    public static bool IsRevealed(Entity observer, EquippedItem item)
    {
        var target = item.Entity;
        var ranked = target.Equipment
            .Where(e => e.Data.HardpointType != HardpointType.Hull)
            .OrderByDescending(e => e.Data.HardpointType != HardpointType.Tool)
            .ThenByDescending(e => e.Data.Shape.Coordinates.Length)
            .ToList();
        var index = ranked.IndexOf(item);
        if (index < 0) return false; // the hull itself, or an item that is no longer on this target

        var settings = observer.ItemManager.GameplaySettings;
        var info = observer.EntityInfoGathered.TryGetValue(target, out var gathered) ? gathered : 0f;
        var tier = lerp(settings.TargetArmorInfoThreshold, settings.TargetGearInfoThreshold,
            (float) index / max(1, ranked.Count - 1));
        return info >= tier;
    }

    // Cut 2, Q4: the stats an entity actually fires with. A working targeting system (equipped, online --
    // not destroyed, not shut down) supplies its own resolved stats; anything else falls back to the
    // authored unaided figures, which make aiming without one a last resort rather than an alternative.
    // Cut 3's roll is the only planned reader.
    public static float Accuracy(Entity entity)
    {
        var system = entity.GetBehavior<TargetingSystem>();
        return system != null && system.Item.Active.Value
            ? system.Accuracy
            : entity.ItemManager.GameplaySettings.UnaidedAccuracy;
    }

    public static float Resolution(Entity entity)
    {
        var system = entity.GetBehavior<TargetingSystem>();
        return system != null && system.Item.Active.Value ? system.Resolution : 1f;
    }

    public static float Precision(Entity entity)
    {
        var system = entity.GetBehavior<TargetingSystem>();
        return system != null && system.Item.Active.Value ? system.Precision : 0f;
    }

    public static float Tracking(Entity entity)
    {
        var system = entity.GetBehavior<TargetingSystem>();
        return system != null && system.Item.Active.Value ? system.Tracking : 0f;
    }
}