import type { Express } from "express";
import { createServer, type Server } from "http";
import { storage } from "./storage";
import { insertSessionSchema } from "@shared/schema";
import { z } from "zod";

export async function registerRoutes(app: Express): Promise<Server> {
  // Create session
  app.post("/api/sessions", async (req, res) => {
    try {
      const sessionData = insertSessionSchema.parse(req.body);
      const session = await storage.createSession(sessionData);
      
      // Update device activity
      await storage.updateDeviceProfileActivity(sessionData.deviceId);
      
      res.status(201).json({ ok: true, id: session.id });
    } catch (error) {
      if (error instanceof z.ZodError) {
        return res.status(400).json({ message: "Invalid session data", errors: error.errors });
      }
      res.status(500).json({ message: "Failed to create session" });
    }
  });

  // Get suggestions for device
  app.get("/api/suggestions", async (req, res) => {
    try {
      const deviceId = req.query.deviceId as string;
      if (!deviceId) {
        return res.status(400).json({ message: "Device ID is required" });
      }

      // Get recent sessions (last 7 days)
      const sevenDaysAgo = new Date();
      sevenDaysAgo.setDate(sevenDaysAgo.getDate() - 7);
      const recentSessions = await storage.getSessionsInDateRange(deviceId, sevenDaysAgo, new Date());
      
      const suggestions = generateSuggestions(recentSessions);
      res.json({ suggestions });
    } catch (error) {
      res.status(500).json({ message: "Failed to get suggestions" });
    }
  });

  // Get stats summary
  app.get("/api/stats/summary", async (req, res) => {
    try {
      const deviceId = req.query.deviceId as string;
      if (!deviceId) {
        return res.status(400).json({ message: "Device ID is required" });
      }

      const sevenDaysAgo = new Date();
      sevenDaysAgo.setDate(sevenDaysAgo.getDate() - 7);
      const thirtyDaysAgo = new Date();
      thirtyDaysAgo.setDate(thirtyDaysAgo.getDate() - 30);

      const last7dSessions = await storage.getSessionsInDateRange(deviceId, sevenDaysAgo, new Date());
      const last30dSessions = await storage.getSessionsInDateRange(deviceId, thirtyDaysAgo, new Date());

      const last7d = calculateStats(last7dSessions.filter(s => s.type === 'focus'));
      const last30d = calculateStats(last30dSessions.filter(s => s.type === 'focus'));

      res.json({ last7d, last30d });
    } catch (error) {
      res.status(500).json({ message: "Failed to get stats" });
    }
  });

  const httpServer = createServer(app);
  return httpServer;
}

function generateSuggestions(sessions: any[]) {
  const focusSessions = sessions.filter(s => s.type === 'focus');
  
  if (focusSessions.length === 0) {
    return [
      { minutes: 25, reason: "Classic Pomodoro technique - great for starting out." },
      { minutes: 15, reason: "Short sprints help build focus habits." },
      { minutes: 40, reason: "Extended sessions for deep work." }
    ];
  }

  const completedSessions = focusSessions.filter(s => s.completed);
  const completionRate = completedSessions.length / focusSessions.length;
  
  // Analyze successful durations
  const successfulDurations = completedSessions.map(s => s.intendedMinutes);
  const avgSuccessfulDuration = successfulDurations.reduce((a, b) => a + b, 0) / successfulDurations.length;

  // Analyze time of day patterns
  const now = new Date();
  const currentHour = now.getHours();
  const timeOfDaySuccess = getTimeOfDaySuccess(completedSessions, currentHour);

  const suggestions = [];

  // Primary suggestion based on completion rate
  if (completionRate >= 0.8) {
    suggestions.push({
      minutes: Math.round(avgSuccessfulDuration),
      reason: `Your 7-day completion rate is ${Math.round(completionRate * 100)}% at ${Math.round(avgSuccessfulDuration)}m.`
    });
  } else {
    suggestions.push({
      minutes: 25,
      reason: "Classic 25min sessions have proven effective for most users."
    });
  }

  // Time-based suggestion
  if (timeOfDaySuccess.avgDuration > 0) {
    suggestions.push({
      minutes: Math.round(timeOfDaySuccess.avgDuration),
      reason: `${getTimeOfDayLabel(currentHour)}: best focus avg ${Math.round(timeOfDaySuccess.avgDuration - 3)}–${Math.round(timeOfDaySuccess.avgDuration + 3)}m.`
    });
  }

  // Interruption-based suggestion
  const avgInterruptions = focusSessions.reduce((sum, s) => sum + s.interruptions, 0) / focusSessions.length;
  if (avgInterruptions > 1) {
    suggestions.push({
      minutes: 15,
      reason: "High interruption periods benefit from short sprints."
    });
  } else {
    suggestions.push({
      minutes: 40,
      reason: "Low interruption environment - try longer deep work sessions."
    });
  }

  return suggestions.slice(0, 3);
}

function calculateStats(focusSessions: any[]) {
  const completed = focusSessions.filter(s => s.completed);
  const completionRate = focusSessions.length > 0 ? completed.length / focusSessions.length : 0;
  const avgFocusMin = completed.length > 0 
    ? completed.reduce((sum, s) => sum + s.intendedMinutes, 0) / completed.length 
    : 0;

  return {
    sessions: focusSessions.length,
    completionRate: Math.round(completionRate * 100) / 100,
    avgFocusMin: Math.round(avgFocusMin)
  };
}

function getTimeOfDaySuccess(sessions: any[], currentHour: number) {
  const timeRangeSessions = sessions.filter(s => {
    const sessionHour = new Date(s.startedAt).getHours();
    return Math.abs(sessionHour - currentHour) <= 2;
  });

  if (timeRangeSessions.length === 0) {
    return { avgDuration: 0 };
  }

  const avgDuration = timeRangeSessions.reduce((sum, s) => sum + s.intendedMinutes, 0) / timeRangeSessions.length;
  return { avgDuration };
}

function getTimeOfDayLabel(hour: number) {
  if (hour >= 6 && hour < 12) return "Mornings";
  if (hour >= 12 && hour < 17) return "Afternoons";
  if (hour >= 17 && hour < 21) return "Evenings";
  return "Late hours";
}