using System.Collections.Generic;
using UnityEditor;
using UnityEditor.Animations;
using UnityEngine;
using Ashwild.Player;

namespace Ashwild.EditorTools
{
    /// <summary>
    /// Editor tool that builds the master Animator Controller the player rigs run on. The controller is
    /// authored once and never edited per weapon: every state points at an empty placeholder clip whose
    /// *name* is the slot key, and PlayerAnimationSetBinder swaps those clips at runtime for whatever the
    /// held item authors.
    ///
    /// Generating it rather than clicking it together is not a convenience — the contract between the
    /// controller and PlayerAnimationSet is a set of exact strings (parameter names, clip names), and a
    /// single typo there fails silently: the parameter simply never moves and the rig stands still with
    /// no error to explain why. Encoding the contract in code makes it impossible to get wrong, and lets
    /// the controller be rebuilt from scratch after any manual experiment.
    ///
    /// Placeholder clips are deliberately empty and stored as their own assets rather than reusing a real
    /// animation, so the master controller depends on no FBX and the slot list stays explicit. A slot no
    /// set ever fills therefore plays nothing, which reads as an obvious gap instead of a wrong pose.
    ///
    /// Safe to re-run: it rewrites the controller in place, keeping the asset's GUID so every Animator
    /// already pointing at it stays wired.
    /// </summary>
    public static class PlayerAnimatorControllerBuilder
    {
        #region Constants

        private const string AnimationsFolder = "Assets/GAME/Animations/Arms";
        private const string SlotsFolder = AnimationsFolder + "/Slots";
        private const string ArmsControllerPath = AnimationsFolder + "/PlayerArms.controller";

        /// <summary>
        /// Blend thresholds for the ground tree. They are the gait levels PlayerAnimatorDriver reports —
        /// 0 idle, 1 walk, 2 run — not speeds in metres per second, so retuning how fast the player moves
        /// never desynchronises the animation.
        ///
        /// RunClipSpeed exists only while walk and run share one authored clip: with the same motion in
        /// both slots, playing the run entry faster is the only thing that distinguishes sprinting from
        /// walking. Drop it back to 1 as soon as a real run animation fills the Run slot.
        /// </summary>
        private const float WalkThreshold = 1f;
        private const float RunThreshold = 2f;
        private const float RunClipSpeed = 1.5f;

        private const string SpeedParam = "Speed";
        private const string GroundedParam = "Grounded";
        private const string CrouchingParam = "Crouching";
        private const string SprintingParam = "Sprinting";
        private const string AttackIndexParam = "AttackIndex";
        private const string JumpParam = "Jump";
        private const string LandParam = "Land";
        private const string AttackParam = "Attack";
        private const string GrabParam = "Grab";
        private const string EquipParam = "Equip";
        private const string UnequipParam = "Unequip";

        /// <summary>
        /// Every clip slot the controller declares, in the order a reader should meet them. These strings
        /// are the keys PlayerAnimationSet is queried with — they must match its slot constants exactly.
        /// </summary>
        private static readonly string[] Slots =
        {
            PlayerAnimationSet.SlotIdle,
            PlayerAnimationSet.SlotWalk,
            PlayerAnimationSet.SlotRun,
            PlayerAnimationSet.SlotJumpStart,
            PlayerAnimationSet.SlotJumpLoop,
            PlayerAnimationSet.SlotJumpLand,
            PlayerAnimationSet.SlotGrab,
            PlayerAnimationSet.SlotEquip,
            PlayerAnimationSet.SlotUnequip,
            PlayerAnimationSet.SlotAttackPrefix + "1",
        };

        #endregion

        #region Menu

        /// <summary>
        /// Builds (or rebuilds) the first-person arms controller and the placeholder clips it references.
        /// </summary>
        [MenuItem("Tools/Ashwild/Build Player Arms Controller")]
        public static void BuildArmsController()
        {
            EnsureFolders();

            Dictionary<string, AnimationClip> placeholders = new Dictionary<string, AnimationClip>();
            foreach (string slot in Slots)
                placeholders[slot] = GetOrCreatePlaceholder(slot);

            AnimatorController controller = GetOrCreateController(ArmsControllerPath);
            ClearController(controller);
            AddParameters(controller);
            BuildLocomotionLayer(controller, placeholders);
            BuildActionLayer(controller, placeholders);

            EditorUtility.SetDirty(controller);
            AssetDatabase.SaveAssets();
            AssetDatabase.Refresh();

            Debug.Log($"[PlayerAnimatorControllerBuilder] Built {ArmsControllerPath} with {Slots.Length} clip slots. " +
                      "Assign it to the arms Animator, then point PlayerAnimationSetBinder at your Arms_NoItem set.",
                      controller);

            Selection.activeObject = controller;
        }

        #endregion

        #region Layers

        /// <summary>
        /// Base layer: the movement the player is always doing. A 1D blend tree covers ground movement so
        /// idle and run ease into each other instead of snapping, and the jump chain is a straight line
        /// (start → loop → land) driven by the Grounded flag rather than by timers, so a fall the player
        /// never jumped into still enters the loop from Any State.
        /// </summary>
        private static void BuildLocomotionLayer(AnimatorController controller, Dictionary<string, AnimationClip> clips)
        {
            AnimatorControllerLayer[] layers = controller.layers;
            layers[0].name = "Locomotion";
            controller.layers = layers;

            AnimatorStateMachine machine = controller.layers[0].stateMachine;

            BlendTree tree;
            AnimatorState locomotion = controller.CreateBlendTreeInController("Locomotion", out tree, 0);
            tree.blendType = BlendTreeType.Simple1D;
            tree.blendParameter = SpeedParam;
            tree.useAutomaticThresholds = false;
            tree.AddChild(clips[PlayerAnimationSet.SlotIdle], 0f);
            tree.AddChild(clips[PlayerAnimationSet.SlotWalk], WalkThreshold);
            tree.AddChild(clips[PlayerAnimationSet.SlotRun], RunThreshold);
            SetChildSpeed(tree, 2, RunClipSpeed);

            AnimatorState jumpStart = machine.AddState(PlayerAnimationSet.SlotJumpStart);
            jumpStart.motion = clips[PlayerAnimationSet.SlotJumpStart];

            AnimatorState jumpLoop = machine.AddState(PlayerAnimationSet.SlotJumpLoop);
            jumpLoop.motion = clips[PlayerAnimationSet.SlotJumpLoop];

            AnimatorState jumpLand = machine.AddState(PlayerAnimationSet.SlotJumpLand);
            jumpLand.motion = clips[PlayerAnimationSet.SlotJumpLand];

            machine.defaultState = locomotion;

            AnimatorStateTransition toJump = locomotion.AddTransition(jumpStart);
            toJump.hasExitTime = false;
            toJump.duration = 0.05f;
            toJump.AddCondition(AnimatorConditionMode.If, 0f, JumpParam);

            AnimatorStateTransition startToLoop = jumpStart.AddTransition(jumpLoop);
            startToLoop.hasExitTime = true;
            startToLoop.exitTime = 0.8f;
            startToLoop.duration = 0.1f;

            AnimatorStateTransition anyToLoop = machine.AddAnyStateTransition(jumpLoop);
            anyToLoop.hasExitTime = false;
            anyToLoop.duration = 0.15f;
            anyToLoop.canTransitionToSelf = false;
            anyToLoop.AddCondition(AnimatorConditionMode.IfNot, 0f, GroundedParam);

            AnimatorStateTransition loopToLand = jumpLoop.AddTransition(jumpLand);
            loopToLand.hasExitTime = false;
            loopToLand.duration = 0.1f;
            loopToLand.AddCondition(AnimatorConditionMode.If, 0f, GroundedParam);

            AnimatorStateTransition landToLocomotion = jumpLand.AddTransition(locomotion);
            landToLocomotion.hasExitTime = true;
            landToLocomotion.exitTime = 0.7f;
            landToLocomotion.duration = 0.15f;
        }

        /// <summary>
        /// Action layer: the one-shots that play *over* whatever the legs are doing. It sits on an empty
        /// default state at full weight, so it contributes nothing until an action fires and the player
        /// keeps running normally underneath. Every action returns to that empty state on exit time,
        /// which is what lets a swing interrupt itself cleanly on the next click.
        /// </summary>
        private static void BuildActionLayer(AnimatorController controller, Dictionary<string, AnimationClip> clips)
        {
            controller.AddLayer("Action");
            AnimatorControllerLayer[] layers = controller.layers;
            AnimatorControllerLayer action = layers[1];
            action.defaultWeight = 1f;
            action.blendingMode = AnimatorLayerBlendingMode.Override;
            controller.layers = layers;

            AnimatorStateMachine machine = action.stateMachine;
            AnimatorState none = machine.AddState("None");
            machine.defaultState = none;

            AddOneShot(machine, none, PlayerAnimationSet.SlotGrab, clips, GrabParam);
            AddOneShot(machine, none, PlayerAnimationSet.SlotEquip, clips, EquipParam);
            AddOneShot(machine, none, PlayerAnimationSet.SlotUnequip, clips, UnequipParam);
            AddOneShot(machine, none, PlayerAnimationSet.SlotAttackPrefix + "1", clips, AttackParam);
        }

        /// <summary>
        /// Wires one action: entered from Any State on its trigger so it can fire at any moment (and
        /// re-fire while already playing, which a combo needs), and released back to the empty state on
        /// exit time so the layer stops contributing as soon as the action is over.
        /// </summary>
        private static void AddOneShot(AnimatorStateMachine machine, AnimatorState none, string slot,
                                       Dictionary<string, AnimationClip> clips, string trigger)
        {
            AnimatorState state = machine.AddState(slot);
            state.motion = clips[slot];

            AnimatorStateTransition enter = machine.AddAnyStateTransition(state);
            enter.hasExitTime = false;
            enter.duration = 0.05f;
            enter.canTransitionToSelf = true;
            enter.AddCondition(AnimatorConditionMode.If, 0f, trigger);

            AnimatorStateTransition exit = state.AddTransition(none);
            exit.hasExitTime = true;
            exit.exitTime = 0.9f;
            exit.duration = 0.1f;
        }

        #endregion

        #region Internal Helpers

        /// <summary>
        /// Sets one blend-tree child's playback rate. The children array must be reassigned wholesale
        /// because BlendTree.children hands back a copy — mutating the returned struct in place silently
        /// does nothing.
        /// </summary>
        private static void SetChildSpeed(BlendTree tree, int index, float speed)
        {
            ChildMotion[] children = tree.children;
            if (index < 0 || index >= children.Length) return;
            children[index].timeScale = speed;
            tree.children = children;
        }

        /// <summary>
        /// Declares every parameter PlayerAnimatorDriver writes. Names are the ones the driver defaults
        /// to, so a freshly added driver works with no inspector edits.
        /// </summary>
        private static void AddParameters(AnimatorController controller)
        {
            controller.AddParameter(SpeedParam, AnimatorControllerParameterType.Float);
            controller.AddParameter(GroundedParam, AnimatorControllerParameterType.Bool);
            controller.AddParameter(CrouchingParam, AnimatorControllerParameterType.Bool);
            controller.AddParameter(SprintingParam, AnimatorControllerParameterType.Bool);
            controller.AddParameter(AttackIndexParam, AnimatorControllerParameterType.Int);
            controller.AddParameter(JumpParam, AnimatorControllerParameterType.Trigger);
            controller.AddParameter(LandParam, AnimatorControllerParameterType.Trigger);
            controller.AddParameter(AttackParam, AnimatorControllerParameterType.Trigger);
            controller.AddParameter(GrabParam, AnimatorControllerParameterType.Trigger);
            controller.AddParameter(EquipParam, AnimatorControllerParameterType.Trigger);
            controller.AddParameter(UnequipParam, AnimatorControllerParameterType.Trigger);

            SetDefaultBool(controller, GroundedParam, true);
        }

        /// <summary>
        /// Seeds a bool's authored default so the rig starts in a sane pose on the very first frame,
        /// before the driver has pushed anything — a player spawning "not grounded" would otherwise flash
        /// the fall loop.
        /// </summary>
        private static void SetDefaultBool(AnimatorController controller, string paramName, bool value)
        {
            AnimatorControllerParameter[] parameters = controller.parameters;
            for (int i = 0; i < parameters.Length; i++)
            {
                if (parameters[i].name != paramName) continue;
                parameters[i].defaultBool = value;
                break;
            }
            controller.parameters = parameters;
        }

        /// <summary>
        /// Empties an existing controller so a rebuild never stacks duplicate states or parameters on top
        /// of the previous run. The asset itself is kept so its GUID — and every Animator reference to
        /// it — survives.
        /// </summary>
        private static void ClearController(AnimatorController controller)
        {
            for (int i = controller.layers.Length - 1; i > 0; i--)
                controller.RemoveLayer(i);

            while (controller.parameters.Length > 0)
                controller.RemoveParameter(0);

            AnimatorStateMachine machine = controller.layers[0].stateMachine;

            for (int i = machine.states.Length - 1; i >= 0; i--)
                machine.RemoveState(machine.states[i].state);

            for (int i = machine.anyStateTransitions.Length - 1; i >= 0; i--)
                machine.RemoveAnyStateTransition(machine.anyStateTransitions[i]);
        }

        /// <summary>
        /// Loads the controller at a path, creating it on first run.
        /// </summary>
        private static AnimatorController GetOrCreateController(string path)
        {
            AnimatorController existing = AssetDatabase.LoadAssetAtPath<AnimatorController>(path);
            return existing != null ? existing : AnimatorController.CreateAnimatorControllerAtPath(path);
        }

        /// <summary>
        /// Loads (or creates) the empty clip that stands in for a slot. Its name is the slot key the
        /// binder matches sets against, which is the whole reason these exist as named assets.
        /// </summary>
        private static AnimationClip GetOrCreatePlaceholder(string slot)
        {
            string path = $"{SlotsFolder}/{slot}.anim";
            AnimationClip existing = AssetDatabase.LoadAssetAtPath<AnimationClip>(path);
            if (existing != null) return existing;

            AnimationClip clip = new AnimationClip { name = slot };
            AssetDatabase.CreateAsset(clip, path);
            return clip;
        }

        /// <summary>
        /// Makes sure the target folders exist before anything is written into them.
        /// </summary>
        private static void EnsureFolders()
        {
            if (!AssetDatabase.IsValidFolder(AnimationsFolder))
            {
                Debug.LogError($"[PlayerAnimatorControllerBuilder] '{AnimationsFolder}' does not exist — create it first.");
                return;
            }

            if (!AssetDatabase.IsValidFolder(SlotsFolder))
                AssetDatabase.CreateFolder(AnimationsFolder, "Slots");
        }

        #endregion
    }
}