// Assets/_Project/Scripts/Dev/DebugConsoleUI.cs
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UIElements;

namespace TD.Dev
{
    /// <summary>
    /// Builds and draws <see cref="DebugConsole"/>'s VisualElement tree: the input bar and
    /// its autocomplete list. Owns presentation only — element construction, styling, and
    /// row rendering — no command grammar, keybinding, or suggestion-selection logic; that
    /// stays in <see cref="DebugConsole"/>, which drives this class through its public
    /// members and reads/writes <see cref="CommandInput"/> directly for focus and value.
    /// </summary>
    internal sealed class DebugConsoleUI
    {
        // Beyond this many candidates the list is truncated with a "+N more" row so a
        // large DraftPool can't grow the console bar off the top of the screen.
        private const int MaxVisibleSuggestions = 12;

        /// <summary>One row of the autocomplete list: a candidate token plus an optional dim hint.</summary>
        public readonly struct SuggestionRow
        {
            public readonly string Text;
            public readonly string Hint;

            public SuggestionRow(string text, string hint)
            {
                Text = text;
                Hint = hint;
            }
        }

        public TextField CommandInput { get; }

        private readonly VisualElement consoleContainer;
        private readonly VisualElement suggestionList;

        public DebugConsoleUI(VisualElement uiRoot)
        {
            // Top-anchored bar, closed by default. Distinct position from the HUD's
            // bottom-left chat panel so the two never overlap.
            consoleContainer = new VisualElement();
            consoleContainer.pickingMode = PickingMode.Ignore;
            consoleContainer.style.position = Position.Absolute;
            consoleContainer.style.left = 0;
            consoleContainer.style.right = 0;
            consoleContainer.style.top = 0;
            consoleContainer.style.paddingTop = 8;
            consoleContainer.style.paddingBottom = 8;
            consoleContainer.style.paddingLeft = 12;
            consoleContainer.style.paddingRight = 12;
            // Fully opaque: the console is a text-entry overlay that has to stay readable
            // over the level, the HUD, and whatever else is on screen.
            consoleContainer.style.backgroundColor = new Color(0f, 0f, 0f, 1f);
            consoleContainer.style.display = DisplayStyle.None;

            CommandInput = new TextField();
            CommandInput.style.minHeight = 28;
            CommandInput.style.width = Length.Percent(100);
            CommandInput.maxLength = 200;
            CommandInput.isDelayed = false;
            StyleConsoleInput(CommandInput);

            suggestionList = new VisualElement();
            suggestionList.pickingMode = PickingMode.Ignore;
            suggestionList.style.flexDirection = FlexDirection.Column;
            suggestionList.style.marginTop = 4;
            suggestionList.style.display = DisplayStyle.None;

            consoleContainer.Add(CommandInput);
            consoleContainer.Add(suggestionList);
            uiRoot.Add(consoleContainer);
        }

        // Mirrors HUDController.StyleChatInputDark — dark background, white text,
        // a thin border, and inner padding so ascenders/descenders don't clip.
        // Green border (vs. chat's neutral gray) as a quick visual "this is the
        // debug console, not chat" cue.
        private static void StyleConsoleInput(TextField field)
        {
            var darkBg = new Color(0.05f, 0.05f, 0.05f, 1f);
            var borderClr = new Color(0.35f, 0.75f, 0.35f);

            field.style.backgroundColor = darkBg;
            field.style.color = Color.white;
            field.style.borderTopWidth = field.style.borderBottomWidth =
                field.style.borderLeftWidth = field.style.borderRightWidth = 1;
            field.style.borderTopColor = field.style.borderBottomColor =
                field.style.borderLeftColor = field.style.borderRightColor = borderClr;

            var inner = field.Q("unity-text-input");
            if (inner != null)
            {
                inner.style.backgroundColor = darkBg;
                inner.style.color = Color.white;
                inner.style.paddingTop = 4;
                inner.style.paddingBottom = 4;
                inner.style.paddingLeft = 6;
                inner.style.paddingRight = 6;
            }
        }

        // One autocomplete row: the candidate token plus an optional dim hint. Rows are
        // pickingMode Ignore and keyboard-driven only — nothing here is clickable, which
        // avoids the recursive picking-mode problem documented in HUDController's chat
        // panel (clicks falling through to the game world via a ScrollView's internal
        // wrapper element).
        private static VisualElement BuildSuggestionRow(string text, string hint, bool selected)
        {
            var row = new VisualElement();
            row.pickingMode = PickingMode.Ignore;
            row.style.flexDirection = FlexDirection.Row;
            row.style.minHeight = 20;
            row.style.paddingLeft = 6;
            row.style.paddingRight = 6;
            row.style.backgroundColor = selected
                ? new Color(0.16f, 0.38f, 0.16f, 1f)   // matches the green console cue
                : new Color(0.05f, 0.05f, 0.05f, 1f);

            var label = new Label(text);
            label.pickingMode = PickingMode.Ignore;
            label.style.color = Color.white;
            label.style.unityFontStyleAndWeight = selected ? FontStyle.Bold : FontStyle.Normal;
            row.Add(label);

            if (!string.IsNullOrEmpty(hint))
            {
                var hintLabel = new Label(hint);
                hintLabel.pickingMode = PickingMode.Ignore;
                hintLabel.style.color = new Color(0.6f, 0.6f, 0.6f);
                hintLabel.style.marginLeft = 12;
                row.Add(hintLabel);
            }

            return row;
        }

        public void Show()
        {
            consoleContainer.style.display = DisplayStyle.Flex;
            consoleContainer.pickingMode = PickingMode.Position;
        }

        public void Hide()
        {
            consoleContainer.style.display = DisplayStyle.None;
            consoleContainer.pickingMode = PickingMode.Ignore;
        }

        // Windows the list around selectedIndex so arrowing past MaxVisibleSuggestions
        // keeps the selected row on screen instead of scrolling it out of the truncated view.
        public void RenderSuggestions(List<SuggestionRow> rows, int selectedIndex)
        {
            suggestionList.Clear();

            if (rows == null || rows.Count == 0)
            {
                suggestionList.style.display = DisplayStyle.None;
                return;
            }

            suggestionList.style.display = DisplayStyle.Flex;

            int start = rows.Count > MaxVisibleSuggestions
                ? Mathf.Clamp(selectedIndex - MaxVisibleSuggestions / 2, 0,
                              rows.Count - MaxVisibleSuggestions)
                : 0;
            int end = Mathf.Min(start + MaxVisibleSuggestions, rows.Count);

            for (int i = start; i < end; i++)
                suggestionList.Add(BuildSuggestionRow(rows[i].Text, rows[i].Hint, i == selectedIndex));

            int hidden = rows.Count - (end - start);
            if (hidden > 0)
                suggestionList.Add(BuildSuggestionRow($"+{hidden} more", null, false));
        }

        public void ClearSuggestions()
        {
            suggestionList.Clear();
            suggestionList.style.display = DisplayStyle.None;
        }
    }
}