import "dart:convert";

import "session_types.dart";

// in-memory conversation history for the current session
// does not auto-persist - caller has to call SessionStore.saveSession
class ConversationHistory {
  ConversationHistory({ConversationSession? session}) : _session = session;

  ConversationSession? _session;

  ConversationSession? get session => _session;

  bool get hasSession => _session != null;

  List<Message> getMessages() {
    return _session?.messages ?? <Message>[];
  }

  void setSession(ConversationSession s) {
    _session = s;
  }

  void addMessage(String role, String content, {int? tokens, int? contextTokens, List<MessageAttachment>? attachments, double? cost}) {
    if (_session == null) return;

    final msg = Message(role: role, content: content, tokens: tokens, contextTokens: contextTokens, attachments: attachments, cost: cost);

    _session!.messages.add(msg);
    _session!.updated = DateTime.now().toUtc();
  }

  void appendToLastMessage(String text) {
    if (_session == null || _session!.messages.isEmpty || text.isEmpty) {
      return;
    }

    final lastMessage = _session!.messages.last;
    _session!.messages[_session!.messages.length - 1] = Message(
      role: lastMessage.role,
      content: "${lastMessage.content}$text",
      timestamp: lastMessage.timestamp,
      tokens: lastMessage.tokens,
      contextTokens: lastMessage.contextTokens,
    );
    _session!.updated = DateTime.now().toUtc();
  }

  void setLastMessageContextTokens(int? contextTokens) {
    if (_session == null || _session!.messages.isEmpty) return;
    final last = _session!.messages.last;
    _session!.messages[_session!.messages.length - 1] = Message(
      role: last.role,
      content: last.content,
      timestamp: last.timestamp,
      tokens: last.tokens,
      contextTokens: contextTokens ?? last.contextTokens,
      cost: last.cost,
    );
  }

  void setLastMessageCost(double? cost) {
    if (_session == null || _session!.messages.isEmpty) return;
    final last = _session!.messages.last;
    _session!.messages[_session!.messages.length - 1] = Message(
      role: last.role,
      content: last.content,
      timestamp: last.timestamp,
      tokens: last.tokens,
      contextTokens: last.contextTokens,
      cost: cost,
    );
  }

  void removeLastMessage() {
    if (_session == null || _session!.messages.isEmpty) {
      return;
    }

    _session!.messages.removeLast();
    _session!.updated = DateTime.now().toUtc();
  }

  void truncateMessages(int length) {
    if (_session == null) {
      return;
    }

    final targetLength = length.clamp(0, _session!.messages.length);
    _session!.messages.removeRange(targetLength, _session!.messages.length);
    _session!.updated = DateTime.now().toUtc();
  }

  // remove all messages but keep the session metadata
  void clear() {
    if (_session == null) return;
    _session!.messages.clear();
    _session!.updated = DateTime.now().toUtc();
  }

  // export as plain text - one [role]: content block per message
  String exportToText() {
    final buf = StringBuffer();

    if (_session != null) {
      buf.writeln("Session: ${_session!.name}");
      buf.writeln("ID: ${_session!.id}");
      buf.writeln("Created: ${_session!.created.toIso8601String()}");
      buf.writeln("Messages: ${_session!.messageCount}");
      buf.writeln("---");
      buf.writeln();
    }

    for (final msg in getMessages()) {
      buf.writeln("[${msg.role}]");
      buf.writeln(msg.content);
      buf.writeln();
    }

    return buf.toString();
  }

  String exportToJson() {
    if (_session == null) {
      return const JsonEncoder.withIndent(
        "  ",
      ).convert(<String, dynamic>{"messages": <dynamic>[]});
    }

    return const JsonEncoder.withIndent("  ").convert(_session!.toJson());
  }
}