using System.IO;
using TMPro;
using UnityEngine;
using UnityEngine.UI;
using UnityEngine.SceneManagement;

namespace QuestAppLauncher
{
    /// <summary>
    /// Applies managed branding from <see cref="ManagedPolicyHandler.Branding"/>
    /// to the launcher UI at startup and whenever new tabs are created.
    ///
    /// No Unity Editor wiring required — all GameObjects are located by their
    /// scene names at runtime.
    ///
    /// <para>
    /// Default colours (original art):
    /// Primary <c>#3E6DA9</c> · Accent <c>#00AEEF</c>
    /// </para>
    /// </summary>
    public class BrandingHandler : MonoBehaviour
    {
        // Known GameObject / child names from the scene
        const string TopTabContentName   = "Top_Tab_Content";
        const string LeftTabContentName  = "Left_Tab_Content";
        const string RightTabContentName = "Right_Tab_Content";
        const string LogoObjectName      = "Branding_Logo";     // created at runtime if absent
        const string TitleObjectName     = "Branding_Title";    // created at runtime if absent
        const string CanvasName          = "Canvas";

        // Original art colours — used when no policy is active
        const string DefaultPrimary = "#3E6DA9";
        const string DefaultAccent  = "#00AEEF";

        /// <summary>Current primary colour (tab backgrounds).</summary>
        public static Color PrimaryColor { get; private set; }
        /// <summary>Current accent colour (selected-tab indicator).</summary>
        public static Color AccentColor  { get; private set; }

        // ─────────────────────────────────────────────────────────────────────

        /// <summary>
        /// Automatically creates a persistent BrandingHandler GameObject on startup.
        /// No scene setup or Unity Editor wiring required.
        /// </summary>
        [RuntimeInitializeOnLoadMethod(RuntimeInitializeLoadType.AfterSceneLoad)]
        private static void AutoInstall()
        {
            if (FindFirstObjectByType<BrandingHandler>() != null) return;
            var go = new GameObject("BrandingHandler");
            DontDestroyOnLoad(go);
            go.AddComponent<BrandingHandler>();
        }

        void Start()
        {
            var branding = ManagedPolicyHandler.Branding;

            PrimaryColor = ParseColor(branding?.PrimaryColor, DefaultPrimary);
            AccentColor  = ParseColor(branding?.AccentColor,  DefaultAccent);

            ApplyLogo(branding?.LogoPath);
            ApplyTitle(branding?.AppTitle);

            // Recolour tabs already in the scene (tabs are also re-coloured by
            // GridPopulation after it creates them, covering the dynamic case)
            ApplyToTabParent(GameObject.Find(TopTabContentName));
            ApplyToTabParent(GameObject.Find(LeftTabContentName));
            ApplyToTabParent(GameObject.Find(RightTabContentName));
        }

        // ── Public API ────────────────────────────────────────────────────────

        /// <summary>
        /// Recolours every tab child of <paramref name="tabParent"/>.
        /// Called by <see cref="GridPopulation"/> after it populates each tab container.
        /// </summary>
        public void ApplyToTabParent(GameObject tabParent)
        {
            if (tabParent == null) return;
            foreach (Transform tab in tabParent.transform)
                ApplyToTab(tab.gameObject);
        }

        /// <summary>
        /// Applies branding colours to a single tab (Tab.prefab structure:
        /// Toggle root with <c>Background</c> and <c>Checkmark</c> children).
        /// </summary>
        public void ApplyToTab(GameObject tab)
        {
            if (tab == null) return;

            var bg = tab.transform.Find("Background");
            if (bg != null)
            {
                var img = bg.GetComponent<Image>();
                if (img != null) img.color = PrimaryColor;
            }

            var check = tab.transform.Find("Checkmark");
            if (check != null)
            {
                var img = check.GetComponent<Image>();
                if (img != null) img.color = AccentColor;
            }

            var toggle = tab.GetComponent<Toggle>();
            if (toggle != null)
            {
                var cb = toggle.colors;
                cb.normalColor      = PrimaryColor;
                cb.highlightedColor = Brighten(PrimaryColor, 0.15f);
                cb.pressedColor     = Darken(PrimaryColor,   0.15f);
                cb.selectedColor    = AccentColor;
                toggle.colors       = cb;
            }
        }

        // ── Logo & title ──────────────────────────────────────────────────────

        private void ApplyLogo(string logoPath)
        {
            if (string.IsNullOrEmpty(logoPath) || !File.Exists(logoPath)) return;

            var bytes = File.ReadAllBytes(logoPath);
            var tex   = new Texture2D(2, 2, TextureFormat.RGBA32, false);
            tex.filterMode = FilterMode.Bilinear;
            if (!tex.LoadImage(bytes)) return;

            var logoObj = GetOrCreateUIImage(LogoObjectName, new Vector2(400, 100), new Vector2(0, 60));
            var img = logoObj.GetComponent<Image>();
            img.sprite          = Sprite.Create(tex, new Rect(0, 0, tex.width, tex.height), new Vector2(0.5f, 0.5f));
            img.color           = Color.white;
            img.preserveAspect  = true;
            logoObj.SetActive(true);
        }

        private void ApplyTitle(string title)
        {
            if (string.IsNullOrEmpty(title)) return;

            // Re-use an existing Branding_Title object or create one
            var existing = GameObject.Find(TitleObjectName);
            TextMeshProUGUI tmp;

            if (existing == null)
            {
                var canvas = GameObject.Find(CanvasName);
                if (canvas == null) return;

                existing = new GameObject(TitleObjectName);
                existing.transform.SetParent(canvas.transform, false);

                var rt = existing.AddComponent<RectTransform>();
                rt.anchorMin        = new Vector2(0.5f, 1f);
                rt.anchorMax        = new Vector2(0.5f, 1f);
                rt.pivot            = new Vector2(0.5f, 1f);
                rt.anchoredPosition = new Vector2(0, -10);
                rt.sizeDelta        = new Vector2(800, 80);

                tmp = existing.AddComponent<TextMeshProUGUI>();
                tmp.fontSize    = 48;
                tmp.fontStyle   = FontStyles.Bold;
                tmp.alignment   = TextAlignmentOptions.Center;
                tmp.color       = Color.white;
            }
            else
            {
                tmp = existing.GetComponent<TextMeshProUGUI>();
                if (tmp == null) tmp = existing.AddComponent<TextMeshProUGUI>();
            }

            tmp.text = title;
            existing.SetActive(true);
        }

        // ── Helpers ───────────────────────────────────────────────────────────

        /// <summary>
        /// Finds an existing Image GameObject by name, or creates one anchored to the
        /// top-centre of the Canvas.
        /// </summary>
        private GameObject GetOrCreateUIImage(string objName, Vector2 size, Vector2 anchoredPos)
        {
            var existing = GameObject.Find(objName);
            if (existing != null) return existing;

            var canvas = GameObject.Find(CanvasName);
            if (canvas == null) return new GameObject(objName); // fallback

            var obj = new GameObject(objName);
            obj.transform.SetParent(canvas.transform, false);

            var rt = obj.AddComponent<RectTransform>();
            rt.anchorMin        = new Vector2(0.5f, 1f);
            rt.anchorMax        = new Vector2(0.5f, 1f);
            rt.pivot            = new Vector2(0.5f, 1f);
            rt.anchoredPosition = anchoredPos;
            rt.sizeDelta        = size;

            obj.AddComponent<Image>();
            return obj;
        }

        // ── Colour utilities ──────────────────────────────────────────────────

        private static Color ParseColor(string hex, string fallback)
        {
            if (!string.IsNullOrEmpty(hex) && TryParseHex(hex, out var c)) return c;
            if (!string.IsNullOrEmpty(fallback) && TryParseHex(fallback, out var f)) return f;
            return Color.white;
        }

        private static bool TryParseHex(string hex, out Color color)
        {
            color = Color.white;
            hex = hex?.TrimStart('#');
            if (hex == null || (hex.Length != 6 && hex.Length != 8)) return false;
            try
            {
                byte r = System.Convert.ToByte(hex.Substring(0, 2), 16);
                byte g = System.Convert.ToByte(hex.Substring(2, 2), 16);
                byte b = System.Convert.ToByte(hex.Substring(4, 2), 16);
                byte a = hex.Length == 8 ? System.Convert.ToByte(hex.Substring(6, 2), 16) : (byte)255;
                color = new Color32(r, g, b, a);
                return true;
            }
            catch { return false; }
        }

        private static Color Brighten(Color c, float v) =>
            new Color(Mathf.Clamp01(c.r + v), Mathf.Clamp01(c.g + v), Mathf.Clamp01(c.b + v), c.a);

        private static Color Darken(Color c, float v) =>
            new Color(Mathf.Clamp01(c.r - v), Mathf.Clamp01(c.g - v), Mathf.Clamp01(c.b - v), c.a);
    }
}