import React from 'react';
import { Box, Text, useInput } from 'ink';
import type { ConversationSummary } from '../hooks/use-conversations.js';

export interface SidebarProps {
  conversations: ConversationSummary[];
  activeConversationId: string | undefined;
  selectedIndex: number;
  onSelectIndex: (index: number) => void;
  onSwitchConversation: (id: string) => void;
  onDeleteConversation: (id: string) => void;
  loading: boolean;
  focused: boolean;
  width: number;
}

function formatRelativeTime(dateStr: string): string {
  const date = new Date(dateStr);
  const now = new Date();
  const diffMs = now.getTime() - date.getTime();
  const diffDays = Math.floor(diffMs / (1000 * 60 * 60 * 24));

  if (diffDays === 0) {
    const hh = String(date.getHours()).padStart(2, '0');
    const mm = String(date.getMinutes()).padStart(2, '0');
    return `${hh}:${mm}`;
  }
  if (diffDays < 7) {
    return `${diffDays}d ago`;
  }
  const months = [
    'Jan',
    'Feb',
    'Mar',
    'Apr',
    'May',
    'Jun',
    'Jul',
    'Aug',
    'Sep',
    'Oct',
    'Nov',
    'Dec',
  ];
  const mon = months[date.getMonth()];
  const dd = String(date.getDate()).padStart(2, '0');
  return `${mon} ${dd}`;
}

function truncate(text: string, maxLen: number): string {
  if (text.length <= maxLen) return text;
  return text.slice(0, maxLen - 1) + '…';
}

export function Sidebar({
  conversations,
  activeConversationId,
  selectedIndex,
  onSelectIndex,
  onSwitchConversation,
  onDeleteConversation,
  loading,
  focused,
  width,
}: SidebarProps) {
  useInput(
    (_input, key) => {
      if (key.upArrow) {
        onSelectIndex(Math.max(0, selectedIndex - 1));
      }
      if (key.downArrow) {
        onSelectIndex(Math.min(conversations.length - 1, selectedIndex + 1));
      }
      if (key.return) {
        const conv = conversations[selectedIndex];
        if (conv) {
          onSwitchConversation(conv.id);
        }
      }
      if (_input === 'd') {
        const conv = conversations[selectedIndex];
        if (conv) {
          onDeleteConversation(conv.id);
        }
      }
    },
    { isActive: focused },
  );

  const borderColor = focused ? 'cyan' : 'gray';
  // Available width for content inside border + padding
  const innerWidth = width - 4; // 2 border + 2 padding

  return (
    <Box
      flexDirection="column"
      width={width}
      borderStyle="single"
      borderColor={borderColor}
      paddingX={1}
    >
      <Text bold color="cyan">
        Conversations
      </Text>
      <Box marginTop={0} flexDirection="column" flexGrow={1}>
        {loading && conversations.length === 0 ? (
          <Text dimColor>Loading…</Text>
        ) : conversations.length === 0 ? (
          <Text dimColor>No conversations</Text>
        ) : (
          conversations.map((conv, idx) => {
            const isActive = conv.id === activeConversationId;
            const isSelected = idx === selectedIndex && focused;
            const marker = isActive ? '● ' : '  ';
            const time = formatRelativeTime(conv.updatedAt);
            const title = conv.title ?? 'Untitled';
            // marker(2) + title + space(1) + time
            const maxTitleLen = Math.max(4, innerWidth - marker.length - time.length - 1);
            const displayTitle = truncate(title, maxTitleLen);

            return (
              <Box key={conv.id}>
                <Text
                  inverse={isSelected}
                  color={isActive ? 'cyan' : undefined}
                  dimColor={!isActive && !isSelected}
                >
                  {marker}
                  {displayTitle}
                  {' '.repeat(
                    Math.max(0, innerWidth - marker.length - displayTitle.length - time.length),
                  )}
                  {time}
                </Text>
              </Box>
            );
          })
        )}
      </Box>
      {focused && <Text dimColor>↑↓ navigate • enter switch • d delete</Text>}
    </Box>
  );
}