using NozCli.Core.Client;
using NozCli.Core.Config;
using NozCli.Core.Models;

namespace NozCli.Repl;

/// Shared mutable state across the REPL session.
/// Navigation model:
///   ~                       → root, FoldersInView() returns distinct topics
///   ~/psychologie           → topic view, notes filtered by topic
///   ~/biosysteme/subfolder  → slug subfolder within a topic
public class ReplContext
{
    public NozApiClient   Api          { get; }
    public LocalConfig    Config       { get; }
    public List<NoteInfo> NoteCache    { get; set; } = [];
    public bool           Running      { get; set; } = true;

    // Navigation state
    public string? CurrentTopic   { get; set; } = null;  // null = root
    public string? CurrentSubPath { get; set; } = null;  // sub-path within topic

    public string CurrentPath =>
        CurrentTopic is null    ? "~" :
        CurrentSubPath is null  ? $"~/{CurrentTopic}" :
                                  $"~/{CurrentTopic}/{CurrentSubPath}";

    public ReplContext(NozApiClient api, LocalConfig config) { Api = api; Config = config; }

    /// Notes filtered to the current topic (all notes at root).
    public IEnumerable<NoteInfo> NotesInView()
    {
        if (CurrentTopic is null) return NoteCache;

        var topicNotes = NoteCache.Where(n =>
            string.Equals(n.Topic, CurrentTopic, StringComparison.OrdinalIgnoreCase));

        if (CurrentSubPath is null) return topicNotes;

        // Within a subfolder: filter by the slug sub-path relative to topic root
        return topicNotes.Where(n =>
        {
            var rel = SlugRelative(n.Slug);
            return rel.StartsWith(CurrentSubPath + "/") || rel == CurrentSubPath;
        });
    }

    /// Slug of a note relative to the topic root folder.
    /// "biosysteme/bio-regenerative-systeme/hydroponik" under topic "biosysteme"
    /// → "bio-regenerative-systeme/hydroponik"
    public string SlugRelative(string slug)
    {
        if (CurrentTopic is null) return slug;
        var prefix = CurrentTopic + "/";
        return slug.StartsWith(prefix, StringComparison.OrdinalIgnoreCase)
            ? slug[prefix.Length..]
            : slug;
    }

    /// Immediate sub-folders at the current navigation level.
    /// At root: returns distinct topic names.
    /// Within a topic: returns slug sub-segments one level below CurrentSubPath.
    public IEnumerable<string> FoldersInView()
    {
        if (CurrentTopic is null)
            return NoteCache
                .Select(n => n.Topic)
                .Where(t => !string.IsNullOrEmpty(t))
                .Distinct(StringComparer.OrdinalIgnoreCase)!;

        var depth = CurrentSubPath is null ? 0 : CurrentSubPath.Split('/').Length;
        return NotesInView()
            .Where(n => SlugRelative(n.Slug).Split('/').Length > depth + 1)
            .Select(n => SlugRelative(n.Slug).Split('/').ElementAtOrDefault(depth))
            .Where(s => s is not null)
            .Distinct(StringComparer.OrdinalIgnoreCase)!;
    }

    /// Navigate into a topic or sub-folder segment.
    public bool NavigateTo(string segment)
    {
        if (CurrentTopic is null)
        {
            // At root: segment must be a known topic
            var topic = NoteCache
                .Select(n => n.Topic)
                .FirstOrDefault(t => string.Equals(t, segment, StringComparison.OrdinalIgnoreCase));
            if (topic is null) return false;
            CurrentTopic   = topic;
            CurrentSubPath = null;
            return true;
        }

        // Within a topic: segment must be a valid slug sub-folder
        var newSub = CurrentSubPath is null ? segment : $"{CurrentSubPath}/{segment}";
        var hasNotes = NoteCache
            .Where(n => string.Equals(n.Topic, CurrentTopic, StringComparison.OrdinalIgnoreCase))
            .Any(n =>
            {
                var rel = SlugRelative(n.Slug);
                return rel.StartsWith(newSub + "/") || rel == newSub;
            });

        if (!hasNotes) return false;
        CurrentSubPath = newSub;
        return true;
    }

    /// Navigate up one level.
    public void NavigateUp()
    {
        if (CurrentSubPath is not null)
        {
            var parts = CurrentSubPath.Split('/');
            CurrentSubPath = parts.Length > 1 ? string.Join('/', parts[..^1]) : null;
        }
        else
        {
            CurrentTopic = null;
        }
    }

    /// Resolve a short name to a full slug for note commands (cat, edit, rm).
    public string ResolveSlug(string nameOrSlug)
    {
        nameOrSlug = nameOrSlug.TrimEnd('/');
        // Already a full known slug
        if (NoteCache.Any(n => n.Slug == nameOrSlug)) return nameOrSlug;

        if (CurrentTopic is null) return nameOrSlug;

        // Try reconstructing the full slug from relative name
        var topicPrefix = CurrentTopic + "/";
        var sub = CurrentSubPath is null ? nameOrSlug : $"{CurrentSubPath}/{nameOrSlug}";
        var full = topicPrefix + sub;
        if (NoteCache.Any(n => n.Slug == full)) return full;

        // Slug without topic prefix (note stored at root of noosphere)
        if (NoteCache.Any(n => n.Slug == sub)) return sub;

        return nameOrSlug;
    }

    /// Build a slug for a NEW note that doesn't exist yet.
    public string ResolveNewSlug(string nameOrSlug)
    {
        nameOrSlug = nameOrSlug.TrimEnd('/');
        if (nameOrSlug.EndsWith(".md", StringComparison.OrdinalIgnoreCase))
            nameOrSlug = nameOrSlug[..^3];

        if (nameOrSlug.Contains('/')) return nameOrSlug;

        if (CurrentTopic is null) return nameOrSlug;

        var sub = CurrentSubPath is null ? nameOrSlug : $"{CurrentSubPath}/{nameOrSlug}";
        return CurrentTopic + "/" + sub;
    }
}