#!/usr/bin/env -S bun --install=fallback

/**
 * claude-usage - Fast CLI tool to fetch Anthropic Claude usage percentages
 * 
 * Requirements:
 * - Bun runtime
 * - ~/.claude/.credentials.json with valid OAuth token
 * 
 * Usage:
 *   claude-usage
 *   cu          # alias
 *   usage       # alias
 *   ccu         # alias (claude-check-usage)
 */

import { existsSync } from 'fs';
import { join } from 'path';
import { homedir } from 'os';
import chalk from 'chalk';

// Configuration
const CREDENTIALS_PATH = join(homedir(), '.claude', '.credentials.json');

// Parse CLI flags
const args = process.argv.slice(2);
const VERBOSE = args.includes('-v') || args.includes('--verbose') || args.includes('-d') || args.includes('--debug');

interface UsagePeriod {
  utilization: number;
  reset: number;
}

interface UsageData {
  five_hour: UsagePeriod;
  seven_day: UsagePeriod;
}

interface Credentials {
  claudeAiOauth?: {
    accessToken?: string;
  };
}

interface PaceResult {
  diff: number;
  status: string;
}

/**
 * Interpolate between two hex colors
 */
function interpolateColor(color1: string, color2: string, ratio: number): string {
  const r1 = parseInt(color1.slice(1, 3), 16);
  const g1 = parseInt(color1.slice(3, 5), 16);
  const b1 = parseInt(color1.slice(5, 7), 16);
  
  const r2 = parseInt(color2.slice(1, 3), 16);
  const g2 = parseInt(color2.slice(3, 5), 16);
  const b2 = parseInt(color2.slice(5, 7), 16);
  
  const r = Math.round(r1 + (r2 - r1) * ratio);
  const g = Math.round(g1 + (g2 - g1) * ratio);
  const b = Math.round(b1 + (b2 - b1) * ratio);
  
  return `#${r.toString(16).padStart(2, '0')}${g.toString(16).padStart(2, '0')}${b.toString(16).padStart(2, '0')}`;
}

/**
 * Get pastel color based on usage percentage (soft rainbow gradient)
 */
function getColorForPercentage(pct: number): string {
  const stops = [
    { threshold: 0,   color: '#A5D8DD' }, // Soft cyan
    { threshold: 15,  color: '#9DCCB4' }, // Soft teal
    { threshold: 30,  color: '#B8D99A' }, // Soft lime
    { threshold: 45,  color: '#E8D4A2' }, // Soft yellow
    { threshold: 60,  color: '#F4B8A4' }, // Soft orange
    { threshold: 75,  color: '#F5A6A6' }, // Soft red
    { threshold: 85,  color: '#E89999' }, // Medium red
    { threshold: 95,  color: '#D88888' }, // Deeper red
  ];
  
  let lower = stops[0];
  let upper = stops[stops.length - 1];
  
  for (let i = 0; i < stops.length - 1; i++) {
    if (pct >= stops[i].threshold && pct < stops[i + 1].threshold) {
      lower = stops[i];
      upper = stops[i + 1];
      break;
    }
  }
  
  if (pct >= stops[stops.length - 1].threshold) {
    return stops[stops.length - 1].color;
  }
  
  const range = upper.threshold - lower.threshold;
  const position = range > 0 ? (pct - lower.threshold) / range : 0;
  
  return interpolateColor(lower.color, upper.color, position);
}

/**
 * Generate user_id metadata for the request (mimics Claude Code's format)
 */
function generateUserId(accessToken: string): string {
  // Use hash of token as device/user ID
  const hash = Bun.hash(accessToken).toString(16).padStart(64, '0').substring(0, 64);
  
  // Generate a session UUID
  const sessionId = crypto.randomUUID();
  
  return `user_${hash}_session_${sessionId}`;
}

/**
 * Spinner class for loading animation with rainbow gradient
 */
class Spinner {
  private frames = ['⣾', '⣽', '⣻', '⢿', '⡿', '⣟', '⣯', '⣷'];
  private colors = ['#A5D8DD', '#9DCCB4', '#B8D99A', '#E8D4A2', '#F4B8A4', '#F5A6A6'];
  private index = 0;
  private interval: Timer | null = null;
  
  start(message: string) {
    process.stdout.write('\x1B[?25l');
    
    this.interval = setInterval(() => {
      const colorIndex = this.index % this.colors.length;
      const frame = chalk.hex(this.colors[colorIndex])(this.frames[this.index]);
      process.stdout.write(`\r${frame} ${chalk.hex('#9CA3AF')(message)}`);
      this.index = (this.index + 1) % this.frames.length;
    }, 80);
  }
  
  stop() {
    if (this.interval) {
      clearInterval(this.interval);
      process.stdout.write('\r\x1B[K\x1B[?25h');
    }
  }
}

/**
 * Read OAuth token from credentials file
 */
async function readToken(): Promise<string> {
  if (!existsSync(CREDENTIALS_PATH)) {
    throw new Error(`Credentials file not found: ${CREDENTIALS_PATH}\nPlease run 'claude setup-token' first.`);
  }

  const fileContent = Bun.file(CREDENTIALS_PATH);
  const credentials: Credentials = await fileContent.json() as Credentials;

  const token = credentials.claudeAiOauth?.accessToken;
  if (!token) {
    throw new Error('No access token found in credentials file. Please run \'claude setup-token\' to authenticate.');
  }

  return token;
}

/**
 * Fetch usage data by making an API request and reading rate limit headers
 * This request matches what Claude Code sends for checking limit
 */
async function fetchUsage(accessToken: string): Promise<UsageData> {
  const userId = generateUserId(accessToken);
  
  const requestBody = {
    model: 'claude-haiku-4-5-20251001',
    max_tokens: 1,
    messages: [
      {
        role: 'user',
        content: 'limit',
      },
    ],
    metadata: {
      user_id: userId,
    },
  };
  
  const requestHeaders = {
    'Accept': 'application/json',
    'Authorization': `Bearer ${accessToken.substring(0, 20)}...`,
    'anthropic-version': '2023-06-01',
    'anthropic-beta': 'oauth-2025-04-20,interleaved-thinking-2025-05-14',
    'anthropic-dangerous-direct-browser-access': 'true',
    'x-app': 'cli',
    'User-Agent': 'claude-cli/2.0.76 (external, sdk-cli)',
    'Content-Type': 'application/json',
    'accept-language': '*',
    'sec-fetch-mode': 'cors',
    'accept-encoding': 'br, gzip, deflate',
  };
  
  if (VERBOSE) {
    console.log(chalk.hex('#6B7280')('\n=== Debug: API Request ==='));
    console.log(chalk.hex('#9CA3AF')('URL:'), 'https://api.anthropic.com/v1/messages?beta=true');
    console.log(chalk.hex('#9CA3AF')('Method:'), 'POST');
    console.log(chalk.hex('#9CA3AF')('Headers:'), JSON.stringify(requestHeaders, null, 2));
    console.log(chalk.hex('#9CA3AF')('Body:'), JSON.stringify(requestBody, null, 2));
    console.log();
  }
  
  // Make the exact same request Claude Code makes for checking limit
  const response = await fetch('https://api.anthropic.com/v1/messages?beta=true', {
    method: 'POST',
    headers: {
      'Accept': 'application/json',
      'Authorization': `Bearer ${accessToken}`,
      'anthropic-version': '2023-06-01',
      'anthropic-beta': 'oauth-2025-04-20,interleaved-thinking-2025-05-14',
      'anthropic-dangerous-direct-browser-access': 'true',
      'x-app': 'cli',
      'User-Agent': 'claude-cli/2.0.76 (external, sdk-cli)',
      'Content-Type': 'application/json',
      'accept-language': '*',
      'sec-fetch-mode': 'cors',
      'accept-encoding': 'br, gzip, deflate',
    },
    body: JSON.stringify(requestBody),
  });

  if (!response.ok) {
    const text = await response.text();
    throw new Error(`API request failed (${response.status}): ${text.substring(0, 200)}`);
  }

  // Extract rate limit headers from response
  const headers = response.headers;
  const fiveHourUtil = parseFloat(headers.get('anthropic-ratelimit-unified-5h-utilization') || '0');
  const sevenDayUtil = parseFloat(headers.get('anthropic-ratelimit-unified-7d-utilization') || '0');
  const fiveHourReset = parseInt(headers.get('anthropic-ratelimit-unified-5h-reset') || '0');
  const sevenDayReset = parseInt(headers.get('anthropic-ratelimit-unified-7d-reset') || '0');

  if (VERBOSE) {
    console.log(chalk.hex('#6B7280')('=== Debug: Response Headers ==='));
    console.log(chalk.hex('#9CA3AF')('Status:'), response.status, response.statusText);
    
    // Show all response headers
    const allHeaders: Record<string, string> = {};
    headers.forEach((value, key) => {
      allHeaders[key] = value;
    });
    console.log(chalk.hex('#9CA3AF')('All Headers:'), JSON.stringify(allHeaders, null, 2));
    
    console.log(chalk.hex('#6B7280')('\n=== Debug: Parsed Values ==='));
    console.log(chalk.hex('#9CA3AF')('5h utilization:'), fiveHourUtil);
    console.log(chalk.hex('#9CA3AF')('5h reset:'), fiveHourReset, `(${new Date(fiveHourReset * 1000).toLocaleString()})`);
    console.log(chalk.hex('#9CA3AF')('7d utilization:'), sevenDayUtil);
    console.log(chalk.hex('#9CA3AF')('7d reset:'), sevenDayReset, `(${new Date(sevenDayReset * 1000).toLocaleString()})`);
    console.log();
  }

  return {
    five_hour: {
      utilization: fiveHourUtil,
      reset: fiveHourReset,
    },
    seven_day: {
      utilization: sevenDayUtil,
      reset: sevenDayReset,
    },
  };
}

/**
 * Get pastel color for ahead/under pace difference
 */
function getDiffColor(diffPct: number): string {
  if (diffPct > 15) return '#E89999';      // Soft red - way ahead
  if (diffPct > 5) return '#F4B8A4';       // Soft orange - ahead
  if (diffPct >= -5) return '#E8D4A2';     // Soft yellow - on track
  if (diffPct >= -15) return '#B8D99A';    // Soft lime - below (good)
  return '#A5D8DD';                        // Soft cyan - well under limit
}

/**
 * Get pastel color for reset time based on urgency
 */
function getResetColor(resetTimestamp: number): string {
  const now = Date.now() / 1000;
  const hoursRemaining = (resetTimestamp - now) / 3600;
  
  if (hoursRemaining < 1) return '#E89999';      // Soft red - < 1 hour
  if (hoursRemaining < 3) return '#F4B8A4';      // Soft orange - < 3 hours
  if (hoursRemaining < 12) return '#E8D4A2';     // Soft yellow - < 12 hours
  if (hoursRemaining < 48) return '#B8D99A';     // Soft lime - < 2 days
  return '#9DCCB4';                              // Soft teal - plenty of time
}

/**
 * Get status message based on pace difference
 */
function getPaceStatus(diffPct: number): string {
  if (diffPct > 15) return 'high usage rate';
  if (diffPct > 5) return 'slightly elevated';
  if (diffPct >= -5) return 'on track';
  if (diffPct >= -15) return 'comfortable margin';
  return 'well under limit';
}

/**
 * Calculate pace for 5-hour period (linear usage)
 */
function calculate5HourPace(utilization: number, resetTimestamp: number): PaceResult {
  const now = Date.now() / 1000;
  const secondsRemaining = resetTimestamp - now;
  const totalSeconds = 5 * 3600;
  const secondsElapsed = totalSeconds - secondsRemaining;
  
  const expectedUtil = secondsElapsed / totalSeconds;
  const diff = (utilization - expectedUtil) * 100;
  
  return {
    diff,
    status: getPaceStatus(diff)
  };
}

/**
 * Calculate elapsed active hours for 7-day period
 * Active window: 10am-2am (14 hours per day)
 * 2am is the LAST active hour (2:00-2:59am is active)
 */
function calculateElapsedActiveHours(now: Date, reset: Date): number {
  const totalPeriodSeconds = 7 * 24 * 3600;
  const remainingSeconds = (reset.getTime() - now.getTime()) / 1000;
  const elapsedSeconds = totalPeriodSeconds - remainingSeconds;
  
  const completeDays = Math.floor(elapsedSeconds / (24 * 3600));
  
  const currentHour = now.getHours();
  const currentMinute = now.getMinutes();
  
  let activeHoursToday = 0;
  
  if (currentHour >= 10 && currentHour <= 23) {
    activeHoursToday = (currentHour - 10) + (currentMinute / 60);
  } else if (currentHour >= 0 && currentHour <= 2) {
    const hoursAfterMidnight = currentHour + (currentMinute / 60);
    activeHoursToday = 14 + hoursAfterMidnight;
  }
  
  const totalElapsedActiveHours = (completeDays * 14) + Math.min(activeHoursToday, 14);
  
  return totalElapsedActiveHours;
}

/**
 * Calculate pace for 7-day period (accounting for active hours)
 */
function calculate7DayPace(utilization: number, resetTimestamp: number): PaceResult {
  const now = new Date();
  const resetDate = new Date(resetTimestamp * 1000);
  
  const totalActiveHours = 7 * 14;
  const elapsedActiveHours = calculateElapsedActiveHours(now, resetDate);
  
  const expectedUtil = elapsedActiveHours / totalActiveHours;
  const diff = (utilization - expectedUtil) * 100;
  
  return {
    diff,
    status: getPaceStatus(diff)
  };
}

/**
 * Format reset time from Unix timestamp with relative time and contextual absolute time
 */
function formatResetTime(resetTimestamp: number): string {
  if (!resetTimestamp) return '';
  
  const resetDate = new Date(resetTimestamp * 1000); // Convert to milliseconds
  const now = new Date();
  const diffMs = resetDate.getTime() - now.getTime();
  
  if (diffMs < 0) return 'reset overdue';
  
  const diffHours = Math.floor(diffMs / (1000 * 60 * 60));
  const diffMins = Math.floor((diffMs % (1000 * 60 * 60)) / (1000 * 60));
  
  // Format time in local timezone
  const timeStr = resetDate.toLocaleTimeString('en-US', {
    hour: 'numeric',
    minute: '2-digit',
    hour12: true
  });
  
  // Calculate day difference
  const nowDay = new Date(now.getFullYear(), now.getMonth(), now.getDate());
  const resetDay = new Date(resetDate.getFullYear(), resetDate.getMonth(), resetDate.getDate());
  const dayDiff = Math.round((resetDay.getTime() - nowDay.getTime()) / (1000 * 60 * 60 * 24));
  
  let dateContext: string;
  if (dayDiff === 0) {
    dateContext = `${timeStr} today`;
  } else if (dayDiff === 1) {
    dateContext = `${timeStr} tomorrow`;
  } else if (dayDiff < 7) {
    // Day of week (abbreviated)
    const dayNames = ['Sun', 'Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat'];
    const dayName = dayNames[resetDate.getDay()];
    dateContext = `${dayName} ${timeStr}`;
  } else {
    // Check if it's exactly 7 days (same day of week)
    const dayNames = ['Sun', 'Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat'];
    const dayName = dayNames[resetDate.getDay()];
    if (resetDate.getDay() === now.getDay()) {
      dateContext = `next ${dayName} ${timeStr}`;
    } else {
      dateContext = `${dayName} ${timeStr}`;
    }
  }
  
  let relativeTime: string;
  if (diffHours < 24) {
    relativeTime = `${diffHours}h ${diffMins}m`;
  } else {
    const diffDays = Math.floor(diffHours / 24);
    const remainingHours = diffHours % 24;
    relativeTime = `${diffDays}d ${remainingHours}h`;
  }
  
  return `resets in ${relativeTime} (${dateContext})`;
}

/**
 * Format and display usage output with pastel colors and condensed layout
 */
function formatOutput(usage: UsageData): void {
  const fiveHourPct = usage.five_hour.utilization * 100;
  const sevenDayPct = usage.seven_day.utilization * 100;
  
  const fiveHourColor = getColorForPercentage(fiveHourPct);
  const sevenDayColor = getColorForPercentage(sevenDayPct);
  
  const fiveHourReset = formatResetTime(usage.five_hour.reset);
  const sevenDayReset = formatResetTime(usage.seven_day.reset);
  
  const fiveHourResetColor = getResetColor(usage.five_hour.reset);
  const sevenDayResetColor = getResetColor(usage.seven_day.reset);
  
  const fiveHourPace = calculate5HourPace(usage.five_hour.utilization, usage.five_hour.reset);
  const sevenDayPace = calculate7DayPace(usage.seven_day.utilization, usage.seven_day.reset);
  
  const fiveHourDiffColor = getDiffColor(fiveHourPace.diff);
  const sevenDayDiffColor = getDiffColor(sevenDayPace.diff);
  
  const fiveHourPctStr = fiveHourPct.toFixed(2) + '%';
  const sevenDayPctStr = sevenDayPct.toFixed(2) + '%';
  
  const fiveHourDiffStr = (fiveHourPace.diff >= 0 ? '+' : '') + fiveHourPace.diff.toFixed(2) + '%';
  const sevenDayDiffStr = (sevenDayPace.diff >= 0 ? '+' : '') + sevenDayPace.diff.toFixed(2) + '%';
  
  // Pastel color palette
  const headerColor = chalk.hex('#9CA3AF');  // Gray 400 - header
  const labelColor = chalk.hex('#6B7280');   // Gray 500 - period labels
  const bulletColor = chalk.hex('#9CA3AF');  // Gray 400 - bullets
  
  console.log(headerColor('Usage:'));
  console.log(`  ${labelColor('Hourly (5h)')} ${bulletColor('·')} ${chalk.hex(fiveHourColor)(fiveHourPctStr)} ${bulletColor('•')} ${chalk.hex(fiveHourDiffColor)(fiveHourPace.status)} ${chalk.hex(fiveHourDiffColor)(`(${fiveHourDiffStr} ${fiveHourPace.diff >= 0 ? 'ahead' : 'under'})`)} ${bulletColor('•')} ${chalk.hex(fiveHourResetColor)(fiveHourReset)}`);
  console.log(`  ${labelColor('Weekly (7d)')} ${bulletColor('·')} ${chalk.hex(sevenDayColor)(sevenDayPctStr)} ${bulletColor('•')} ${chalk.hex(sevenDayDiffColor)(sevenDayPace.status)} ${chalk.hex(sevenDayDiffColor)(`(${sevenDayDiffStr} ${sevenDayPace.diff >= 0 ? 'ahead' : 'below'})`)} ${bulletColor('•')} ${chalk.hex(sevenDayResetColor)(sevenDayReset)}`);
}

/**
 * Main entry point
 */
async function main() {
  try {
    const spinner = new Spinner();
    
    if (VERBOSE) {
      console.log(chalk.hex('#6B7280')('=== Debug: Configuration ==='));
      console.log(chalk.hex('#9CA3AF')('Credentials path:'), CREDENTIALS_PATH);
      console.log(chalk.hex('#9CA3AF')('Verbose mode:'), VERBOSE);
      console.log();
    }
    
    const accessToken = await readToken();
    
    if (VERBOSE) {
      console.log(chalk.hex('#6B7280')('=== Debug: Authentication ==='));
      console.log(chalk.hex('#9CA3AF')('Token loaded:'), `${accessToken.substring(0, 20)}...${accessToken.substring(accessToken.length - 10)}`);
      console.log(chalk.hex('#9CA3AF')('Token length:'), accessToken.length);
      console.log();
    }

    if (!VERBOSE) {
      spinner.start('Fetching usage data...');
    }
    const usage = await fetchUsage(accessToken);
    if (!VERBOSE) {
      spinner.stop();
    }

    formatOutput(usage);

  } catch (error) {
    if (error instanceof Error) {
      console.error(`Error: ${error.message}`);
    } else {
      console.error('Error: Unknown error occurred');
    }
    process.exit(1);
  }
}

main();