using System.Text;
using System.Text.Json;

namespace ClaudeDo.Ui.Helpers;

public class StreamLineFormatter
{
    private const int MaxLength = 50_000;
    private const int MaxArgChars = 120;

    public string? FormatLine(string line)
    {
        JsonDocument doc;
        try
        {
            doc = JsonDocument.Parse(line);
        }
        catch (JsonException)
        {
            return line;
        }

        using (doc)
        {
            var root = doc.RootElement;
            if (root.ValueKind != JsonValueKind.Object)
                return null;
            if (!root.TryGetProperty("type", out var typeProp))
                return null;

            return typeProp.GetString() switch
            {
                "system"    => FormatSystem(root),
                "assistant" => FormatAssistant(root),
                "user"      => FormatUser(root),
                "result"    => FormatResult(root),
                _           => null,
            };
        }
    }

    private static string? FormatSystem(JsonElement root)
    {
        if (!root.TryGetProperty("subtype", out var subtypeProp))
            return null;

        var subtype = subtypeProp.GetString();
        switch (subtype)
        {
            case "api_retry":
                return "[Retrying API call...]\n";

            case "init":
            {
                var sessionId = root.TryGetProperty("session_id", out var sid)
                    ? sid.GetString() : null;
                var model = root.TryGetProperty("model", out var m)
                    ? m.GetString() : null;

                var shortId = sessionId is { Length: >= 8 }
                    ? sessionId[..8]
                    : sessionId ?? "?";
                var modelPart = string.IsNullOrEmpty(model) ? "" : $" · {model}";
                return $"[session {shortId}{modelPart}]\n";
            }

            default:
                return null;
        }
    }

    private static string? FormatAssistant(JsonElement root)
    {
        if (!TryGetContentArray(root, out var content))
            return null;

        var sb = new StringBuilder();
        foreach (var block in content.EnumerateArray())
        {
            if (block.ValueKind != JsonValueKind.Object) continue;
            if (!block.TryGetProperty("type", out var blockTypeProp)) continue;

            switch (blockTypeProp.GetString())
            {
                case "text":
                    if (block.TryGetProperty("text", out var textProp))
                    {
                        var text = textProp.GetString();
                        if (!string.IsNullOrEmpty(text))
                        {
                            sb.Append(text);
                            if (!text.EndsWith('\n')) sb.Append('\n');
                        }
                    }
                    break;

                case "tool_use":
                    sb.Append(FormatToolUse(block));
                    sb.Append('\n');
                    break;

                case "thinking":
                default:
                    // Filtered.
                    break;
            }
        }

        return sb.Length == 0 ? null : sb.ToString();
    }

    private static bool TryGetContentArray(JsonElement root, out JsonElement content)
    {
        content = default;
        if (!root.TryGetProperty("message", out var message)) return false;
        if (message.ValueKind != JsonValueKind.Object) return false;
        if (!message.TryGetProperty("content", out var c)) return false;
        if (c.ValueKind != JsonValueKind.Array) return false;
        content = c;
        return true;
    }

    private static string? FormatUser(JsonElement root) => null;

    private static string? FormatResult(JsonElement root)
    {
        if (root.TryGetProperty("result", out var resultProp))
            return $"\n--- Result ---\n{resultProp.GetString()}\n";
        return null;
    }

    private static string FormatToolUse(JsonElement block)
    {
        var name = block.TryGetProperty("name", out var nameProp)
            ? nameProp.GetString() ?? "?"
            : "?";

        JsonElement input = default;
        var hasInput = block.TryGetProperty("input", out input)
                       && input.ValueKind == JsonValueKind.Object;

        var label = name;
        if (hasInput && (name == "Task" || name == "Agent"))
        {
            var sub = GetStr(input, "subagent_type");
            if (!string.IsNullOrEmpty(sub))
                label = $"{name}: {sub}";
        }

        string? arg = hasInput ? BuildToolArg(name, input) : null;

        return string.IsNullOrEmpty(arg)
            ? $"[{label}]"
            : $"[{label}] {arg}";
    }

    private static string? BuildToolArg(string toolName, JsonElement input)
    {
        switch (toolName)
        {
            case "Read":
            case "Write":
            case "Edit":
            case "NotebookEdit":
                return Basename(GetStr(input, "file_path"));

            case "Bash":
            case "PowerShell":
            {
                var cmd = GetStr(input, "command");
                return string.IsNullOrEmpty(cmd) ? null : "$ " + Truncate(cmd, MaxArgChars);
            }

            case "Grep":
            {
                var p = GetStr(input, "pattern");
                return string.IsNullOrEmpty(p) ? null : $"\"{Truncate(p, MaxArgChars)}\"";
            }

            case "Glob":
                return Truncate(GetStr(input, "pattern"), MaxArgChars);

            case "Task":
            case "Agent":
                return Truncate(GetStr(input, "description"), MaxArgChars);

            case "WebFetch":
                return GetStr(input, "url");

            case "WebSearch":
            {
                var q = GetStr(input, "query");
                return string.IsNullOrEmpty(q) ? null : $"\"{Truncate(q, MaxArgChars)}\"";
            }

            case "TodoWrite":
                return null;

            default:
                return null;
        }
    }

    private static string? GetStr(JsonElement obj, string name)
        => obj.TryGetProperty(name, out var p) && p.ValueKind == JsonValueKind.String
            ? p.GetString()
            : null;

    private static string Basename(string? path)
    {
        if (string.IsNullOrEmpty(path)) return "";
        var i = path.LastIndexOfAny(new[] { '/', '\\' });
        return i < 0 ? path : path[(i + 1)..];
    }

    private static string Truncate(string? s, int max)
    {
        if (string.IsNullOrEmpty(s)) return "";
        return s.Length <= max ? s : s[..max] + "…";
    }

    public string FormatFile(string filePath)
    {
        var sb = new StringBuilder();
        foreach (var line in File.ReadLines(filePath))
        {
            var formatted = FormatLine(line);
            if (formatted is not null)
                sb.Append(formatted);
        }
        return Trim(sb.ToString());
    }

    public static string Trim(string text)
    {
        if (text.Length <= MaxLength) return text;
        var trimStart = text.Length - MaxLength;
        var newlineAfter = text.IndexOf('\n', trimStart);
        if (newlineAfter >= 0 && newlineAfter < trimStart + 200)
            trimStart = newlineAfter + 1;
        return text[trimStart..];
    }
}