calendar/backend/src/handlers/ics_fetcher.rs

use axum::{
    extract::{Path, State},
    response::Json,
};
use chrono::{DateTime, Utc, Datelike};
use ical::parser::ical::component::IcalEvent;
use reqwest::Client;
use serde::Serialize;
use std::sync::Arc;

use crate::{
    db::ExternalCalendarRepository,
    models::ApiError,
    AppState,
};

// Import VEvent from calendar-models shared crate
use calendar_models::VEvent;

use super::auth::{extract_bearer_token};

#[derive(Debug, Serialize)]
pub struct ExternalCalendarEventsResponse {
    pub events: Vec<VEvent>,
    pub last_fetched: DateTime<Utc>,
}

pub async fn fetch_external_calendar_events(
    headers: axum::http::HeaderMap,
    State(app_state): State<Arc<AppState>>,
    Path(id): Path<i32>,
) -> Result<Json<ExternalCalendarEventsResponse>, ApiError> {
    let token = extract_bearer_token(&headers)?;
    let user = app_state.auth_service.get_user_from_token(&token).await?;

    let repo = ExternalCalendarRepository::new(&app_state.db);
    
    // Get user's external calendars to verify ownership and get URL
    let calendars = repo
        .get_by_user(&user.id)
        .await
        .map_err(|e| ApiError::Database(format!("Failed to get external calendars: {}", e)))?;

    let calendar = calendars
        .into_iter()
        .find(|c| c.id == id)
        .ok_or_else(|| ApiError::NotFound("External calendar not found".to_string()))?;

    if !calendar.is_visible {
        return Ok(Json(ExternalCalendarEventsResponse {
            events: vec![],
            last_fetched: Utc::now(),
        }));
    }

    // Check cache first
    let cache_max_age_minutes = 5;
    let mut ics_content = String::new();
    let mut last_fetched = Utc::now();
    let mut fetched_from_cache = false;

    // Try to get from cache if not stale
    match repo.is_cache_stale(id, cache_max_age_minutes).await {
        Ok(is_stale) => {
            if !is_stale {
                // Cache is fresh, use it
                if let Ok(Some((cached_data, cached_at))) = repo.get_cached_data(id).await {
                    ics_content = cached_data;
                    last_fetched = cached_at;
                    fetched_from_cache = true;
                }
            }
        }
        Err(_) => {
            // If cache check fails, proceed to fetch from URL
        }
    }

    // If not fetched from cache, get from external URL
    if !fetched_from_cache {
        // Log the URL being fetched for debugging
        println!("🌍 Fetching calendar URL: {}", calendar.url);
        
        let user_agents = vec![
            "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/91.0.4472.124 Safari/537.36",
            "Mozilla/5.0 (compatible; Runway Calendar/1.0)",
            "Outlook-iOS/709.2226530.prod.iphone (3.24.1)"
        ];
        
        let mut response = None;
        let mut last_error = None;
        
        // Try different user agents
        for (i, ua) in user_agents.iter().enumerate() {
            println!("🔄 Attempt {} with User-Agent: {}", i + 1, ua);
            
            let client = Client::builder()
                .redirect(reqwest::redirect::Policy::limited(10))
                .timeout(std::time::Duration::from_secs(30))
                .user_agent(*ua)
                .build()
                .map_err(|e| ApiError::Internal(format!("Failed to create HTTP client: {}", e)))?;
            
            let result = client
                .get(&calendar.url)
                .header("Accept", "text/calendar,application/calendar+xml,text/plain,*/*")
                .header("Accept-Charset", "utf-8")
                .header("Cache-Control", "no-cache")
                .send()
                .await;
                
            match result {
                Ok(resp) => {
                    let status = resp.status();
                    println!("📡 Response status: {}", status);
                    if status.is_success() {
                        response = Some(resp);
                        break;
                    } else if status == 400 {
                        // Check if this is an Outlook auth error
                        let error_body = resp.text().await.unwrap_or_default();
                        if error_body.contains("OwaPage") || error_body.contains("Outlook") {
                            println!("🚫 Outlook authentication error detected, trying next approach...");
                            last_error = Some(format!("Outlook auth error: {}", error_body.chars().take(100).collect::<String>()));
                            continue;
                        }
                        last_error = Some(format!("Bad Request: {}", error_body.chars().take(100).collect::<String>()));
                    } else {
                        last_error = Some(format!("HTTP {}", status));
                    }
                }
                Err(e) => {
                    println!("❌ Request failed: {}", e);
                    last_error = Some(format!("Request error: {}", e));
                }
            }
        }
        
        let response = response.ok_or_else(|| {
            ApiError::Internal(format!(
                "Failed to fetch calendar after trying {} different approaches. Last error: {}", 
                user_agents.len(), 
                last_error.unwrap_or("Unknown error".to_string())
            ))
        })?;

        // Response is guaranteed to be successful here since we checked in the loop
        println!("✅ Successfully fetched calendar data");
        
        ics_content = response
            .text()
            .await
            .map_err(|e| ApiError::Internal(format!("Failed to read calendar content: {}", e)))?;

        // Store in cache for future requests
        let etag = None; // TODO: Extract ETag from response headers if available
        if let Err(_) = repo.update_cache(id, &ics_content, etag).await {
            // Log error but don't fail the request
        }

        // Update last_fetched timestamp
        if let Err(_) = repo.update_last_fetched(id, &user.id).await {
        }
        
        last_fetched = Utc::now();
    }

    // Parse ICS content
    let events = parse_ics_content(&ics_content)
        .map_err(|e| ApiError::BadRequest(format!("Failed to parse calendar: {}", e)))?;

    Ok(Json(ExternalCalendarEventsResponse {
        events,
        last_fetched,
    }))
}

fn parse_ics_content(ics_content: &str) -> Result<Vec<VEvent>, Box<dyn std::error::Error>> {
    let reader = ical::IcalParser::new(ics_content.as_bytes());
    let mut events = Vec::new();
    let mut _total_components = 0;
    let mut _failed_conversions = 0;

    for calendar in reader {
        let calendar = calendar?;
        for component in calendar.events {
            _total_components += 1;
            match convert_ical_to_vevent(component) {
                Ok(vevent) => {
                    events.push(vevent);
                }
                Err(_) => {
                    _failed_conversions += 1;
                }
            }
        }
    }

    // Deduplicate events based on UID, start time, and summary
    // Outlook sometimes includes duplicate events (recurring exceptions may appear multiple times)
    events = deduplicate_events(events);

    Ok(events)
}

fn convert_ical_to_vevent(ical_event: IcalEvent) -> Result<VEvent, Box<dyn std::error::Error>> {
    use uuid::Uuid;

    let mut summary = None;
    let mut description = None;
    let mut location = None;
    let mut dtstart = None;
    let mut dtend = None;
    let mut uid = None;
    let mut all_day = false;
    let mut rrule = None;


    // Extract properties
    for property in ical_event.properties {
        match property.name.as_str() {
            "SUMMARY" => {
                summary = property.value;
            }
            "DESCRIPTION" => {
                description = property.value;
            }
            "LOCATION" => {
                location = property.value;
            }
            "DTSTART" => {
                if let Some(value) = property.value {
                    // Check if it's a date-only value (all-day event)
                    if value.len() == 8 && !value.contains('T') {
                        all_day = true;
                        // Parse YYYYMMDD format
                        if let Ok(date) = chrono::NaiveDate::parse_from_str(&value, "%Y%m%d") {
                            dtstart = Some(chrono::TimeZone::from_utc_datetime(&Utc, &date.and_hms_opt(12, 0, 0).unwrap()));
                        }
                    } else {
                        // Extract timezone info from parameters
                        let tzid = property.params.as_ref()
                            .and_then(|params| params.iter().find(|(k, _)| k == "TZID"))
                            .and_then(|(_, v)| v.first().cloned());
                        
                        // Parse datetime with timezone information
                        if let Some(dt) = parse_datetime_with_tz(&value, tzid.as_deref()) {
                            dtstart = Some(dt);
                        }
                    }
                }
            }
            "DTEND" => {
                if let Some(value) = property.value {
                    if all_day && value.len() == 8 && !value.contains('T') {
                        // For all-day events, DTEND is exclusive so use the date as-is at noon
                        if let Ok(date) = chrono::NaiveDate::parse_from_str(&value, "%Y%m%d") {
                            dtend = Some(chrono::TimeZone::from_utc_datetime(&Utc, &date.and_hms_opt(12, 0, 0).unwrap()));
                        }
                    } else {
                        // Extract timezone info from parameters
                        let tzid = property.params.as_ref()
                            .and_then(|params| params.iter().find(|(k, _)| k == "TZID"))
                            .and_then(|(_, v)| v.first().cloned());
                        
                        // Parse datetime with timezone information
                        if let Some(dt) = parse_datetime_with_tz(&value, tzid.as_deref()) {
                            dtend = Some(dt);
                        }
                    }
                }
            }
            "UID" => {
                uid = property.value;
            }
            "RRULE" => {
                rrule = property.value;
            }
            _ => {} // Ignore other properties for now
        }
    }


    let dtstart = dtstart.ok_or("Missing DTSTART")?;

    let vevent = VEvent {
        uid: uid.unwrap_or_else(|| Uuid::new_v4().to_string()),
        dtstart: dtstart.naive_utc(),
        dtstart_tzid: None, // TODO: Parse timezone from ICS
        dtend: dtend.map(|dt| dt.naive_utc()),
        dtend_tzid: None,   // TODO: Parse timezone from ICS
        summary,
        description,
        location,
        all_day,
        rrule,
        rdate: Vec::new(),
        rdate_tzid: None,
        exdate: Vec::new(), // External calendars don't need exception handling
        exdate_tzid: None,
        recurrence_id: None,
        recurrence_id_tzid: None,
        created: None,
        created_tzid: None,
        last_modified: None,
        last_modified_tzid: None,
        dtstamp: Utc::now(),
        sequence: Some(0),
        status: None,
        transp: None,
        organizer: None,
        attendees: Vec::new(),
        url: None,
        attachments: Vec::new(),
        categories: Vec::new(),
        priority: None,
        resources: Vec::new(),
        related_to: None,
        geo: None,
        duration: None,
        class: None,
        contact: None,
        comment: None,
        alarms: Vec::new(),
        etag: None,
        href: None,
        calendar_path: None,
    };

    Ok(vevent)
}

fn parse_datetime_with_tz(datetime_str: &str, tzid: Option<&str>) -> Option<DateTime<Utc>> {
    use chrono::TimeZone;
    use chrono_tz::Tz;
    
    
    // Try various datetime formats commonly found in ICS files
    
    // Format: 20231201T103000Z (UTC) - handle as naive datetime first
    if datetime_str.ends_with('Z') {
        let datetime_without_z = &datetime_str[..datetime_str.len()-1];
        if let Ok(naive_dt) = chrono::NaiveDateTime::parse_from_str(datetime_without_z, "%Y%m%dT%H%M%S") {
            return Some(naive_dt.and_utc());
        }
    }

    // Format: 20231201T103000-0500 (with timezone offset)
    if let Ok(dt) = DateTime::parse_from_str(datetime_str, "%Y%m%dT%H%M%S%z") {
        return Some(dt.with_timezone(&Utc));
    }

    // Format: 2023-12-01T10:30:00Z (ISO format)
    if let Ok(dt) = DateTime::parse_from_str(datetime_str, "%Y-%m-%dT%H:%M:%SZ") {
        return Some(dt.with_timezone(&Utc));
    }

    // Handle naive datetime with timezone parameter
    let naive_dt = if let Ok(dt) = chrono::NaiveDateTime::parse_from_str(datetime_str, "%Y%m%dT%H%M%S") {
        Some(dt)
    } else if let Ok(dt) = chrono::NaiveDateTime::parse_from_str(datetime_str, "%Y-%m-%dT%H:%M:%S") {
        Some(dt)
    } else {
        None
    };

    if let Some(naive_dt) = naive_dt {
        // If TZID is provided, try to parse it
        if let Some(tzid_str) = tzid {
            // Handle common timezone formats
            let tz_result = if tzid_str.starts_with("/mozilla.org/") {
                // Mozilla/Thunderbird format: /mozilla.org/20070129_1/Europe/London
                tzid_str.split('/').last().and_then(|tz_name| tz_name.parse::<Tz>().ok())
            } else if tzid_str.contains('/') {
                // Standard timezone format: America/New_York, Europe/London
                tzid_str.parse::<Tz>().ok()
            } else {
                // Try common abbreviations and Windows timezone names
                match tzid_str {
                    // Standard abbreviations
                    "EST" => Some(Tz::America__New_York),
                    "PST" => Some(Tz::America__Los_Angeles),
                    "MST" => Some(Tz::America__Denver), 
                    "CST" => Some(Tz::America__Chicago),
                    
                    // North America - Windows timezone names to IANA mapping
                    "Mountain Standard Time" => Some(Tz::America__Denver),
                    "Eastern Standard Time" => Some(Tz::America__New_York),
                    "Central Standard Time" => Some(Tz::America__Chicago),
                    "Pacific Standard Time" => Some(Tz::America__Los_Angeles),
                    "Mountain Daylight Time" => Some(Tz::America__Denver),
                    "Eastern Daylight Time" => Some(Tz::America__New_York),
                    "Central Daylight Time" => Some(Tz::America__Chicago),
                    "Pacific Daylight Time" => Some(Tz::America__Los_Angeles),
                    "Hawaiian Standard Time" => Some(Tz::Pacific__Honolulu),
                    "Alaskan Standard Time" => Some(Tz::America__Anchorage),
                    "Alaskan Daylight Time" => Some(Tz::America__Anchorage),
                    "Atlantic Standard Time" => Some(Tz::America__Halifax),
                    "Newfoundland Standard Time" => Some(Tz::America__St_Johns),
                    
                    // Europe
                    "GMT Standard Time" => Some(Tz::Europe__London),
                    "Greenwich Standard Time" => Some(Tz::UTC),
                    "W. Europe Standard Time" => Some(Tz::Europe__Berlin),
                    "Central Europe Standard Time" => Some(Tz::Europe__Warsaw),
                    "Romance Standard Time" => Some(Tz::Europe__Paris),
                    "Central European Standard Time" => Some(Tz::Europe__Belgrade),
                    "E. Europe Standard Time" => Some(Tz::Europe__Bucharest),
                    "FLE Standard Time" => Some(Tz::Europe__Helsinki),
                    "GTB Standard Time" => Some(Tz::Europe__Athens),
                    "Russian Standard Time" => Some(Tz::Europe__Moscow),
                    "Turkey Standard Time" => Some(Tz::Europe__Istanbul),
                    
                    // Asia
                    "China Standard Time" => Some(Tz::Asia__Shanghai),
                    "Tokyo Standard Time" => Some(Tz::Asia__Tokyo),
                    "Korea Standard Time" => Some(Tz::Asia__Seoul),
                    "Singapore Standard Time" => Some(Tz::Asia__Singapore),
                    "India Standard Time" => Some(Tz::Asia__Kolkata),
                    "Pakistan Standard Time" => Some(Tz::Asia__Karachi),
                    "Bangladesh Standard Time" => Some(Tz::Asia__Dhaka),
                    "Thailand Standard Time" => Some(Tz::Asia__Bangkok),
                    "SE Asia Standard Time" => Some(Tz::Asia__Bangkok),
                    "Myanmar Standard Time" => Some(Tz::Asia__Yangon),
                    "Sri Lanka Standard Time" => Some(Tz::Asia__Colombo),
                    "Nepal Standard Time" => Some(Tz::Asia__Kathmandu),
                    "Central Asia Standard Time" => Some(Tz::Asia__Almaty),
                    "West Asia Standard Time" => Some(Tz::Asia__Tashkent),
                    "Afghanistan Standard Time" => Some(Tz::Asia__Kabul),
                    "Iran Standard Time" => Some(Tz::Asia__Tehran),
                    "Arabian Standard Time" => Some(Tz::Asia__Dubai),
                    "Arab Standard Time" => Some(Tz::Asia__Riyadh),
                    "Israel Standard Time" => Some(Tz::Asia__Jerusalem),
                    "Jordan Standard Time" => Some(Tz::Asia__Amman),
                    "Syria Standard Time" => Some(Tz::Asia__Damascus),
                    "Middle East Standard Time" => Some(Tz::Asia__Beirut),
                    "Egypt Standard Time" => Some(Tz::Africa__Cairo),
                    "South Africa Standard Time" => Some(Tz::Africa__Johannesburg),
                    "E. Africa Standard Time" => Some(Tz::Africa__Nairobi),
                    "W. Central Africa Standard Time" => Some(Tz::Africa__Lagos),
                    
                    // Asia Pacific
                    "AUS Eastern Standard Time" => Some(Tz::Australia__Sydney),
                    "AUS Central Standard Time" => Some(Tz::Australia__Darwin),
                    "W. Australia Standard Time" => Some(Tz::Australia__Perth),
                    "Tasmania Standard Time" => Some(Tz::Australia__Hobart),
                    "New Zealand Standard Time" => Some(Tz::Pacific__Auckland),
                    "Fiji Standard Time" => Some(Tz::Pacific__Fiji),
                    "Tonga Standard Time" => Some(Tz::Pacific__Tongatapu),
                    
                    // South America
                    "Argentina Standard Time" => Some(Tz::America__Buenos_Aires),
                    "E. South America Standard Time" => Some(Tz::America__Sao_Paulo),
                    "SA Eastern Standard Time" => Some(Tz::America__Cayenne),
                    "SA Pacific Standard Time" => Some(Tz::America__Bogota),
                    "SA Western Standard Time" => Some(Tz::America__La_Paz),
                    "Pacific SA Standard Time" => Some(Tz::America__Santiago),
                    "Venezuela Standard Time" => Some(Tz::America__Caracas),
                    "Montevideo Standard Time" => Some(Tz::America__Montevideo),
                    
                    // Try parsing as IANA name
                    _ => tzid_str.parse::<Tz>().ok()
                }
            };

            if let Some(tz) = tz_result {
                if let Some(dt_with_tz) = tz.from_local_datetime(&naive_dt).single() {
                    return Some(dt_with_tz.with_timezone(&Utc));
                }
            }
        }
        
        // If no timezone info or parsing failed, treat as UTC (safer than local time assumptions)
        return Some(chrono::TimeZone::from_utc_datetime(&Utc, &naive_dt));
    }

    None
}

/// Deduplicate events based on UID, start time, and summary
/// Some calendar systems (like Outlook) may include duplicate events in ICS feeds
/// This includes both exact duplicates and recurring event instances that would be
/// generated by existing RRULE patterns, and events with same title but different
/// RRULE patterns that should be consolidated
fn deduplicate_events(mut events: Vec<VEvent>) -> Vec<VEvent> {
    use std::collections::HashMap;
    
    let original_count = events.len();
    
    // First pass: Group by UID and prefer recurring events over single events with same UID
    let mut uid_groups: HashMap<String, Vec<VEvent>> = HashMap::new();
    
    for event in events.drain(..) {
        // Debug logging to understand what's happening
        println!("🔍 Event: '{}' at {} (RRULE: {}) - UID: {}", 
            event.summary.as_ref().unwrap_or(&"No Title".to_string()),
            event.dtstart.format("%Y-%m-%d %H:%M"),
            if event.rrule.is_some() { "Yes" } else { "No" },
            event.uid
        );
        
        uid_groups.entry(event.uid.clone()).or_insert_with(Vec::new).push(event);
    }
    
    let mut uid_deduplicated_events = Vec::new();
    
    for (uid, mut events_with_uid) in uid_groups.drain() {
        if events_with_uid.len() == 1 {
            // Only one event with this UID, keep it
            uid_deduplicated_events.push(events_with_uid.into_iter().next().unwrap());
        } else {
            // Multiple events with same UID - prefer recurring over non-recurring
            println!("🔍 Found {} events with UID '{}'", events_with_uid.len(), uid);
            
            // Sort by preference: recurring events first, then by completeness
            events_with_uid.sort_by(|a, b| {
                let a_has_rrule = a.rrule.is_some();
                let b_has_rrule = b.rrule.is_some();
                
                match (a_has_rrule, b_has_rrule) {
                    (true, false) => std::cmp::Ordering::Less,   // a (recurring) comes first
                    (false, true) => std::cmp::Ordering::Greater, // b (recurring) comes first
                    _ => {
                        // Both same type (both recurring or both single) - compare by completeness
                        event_completeness_score(b).cmp(&event_completeness_score(a))
                    }
                }
            });
            
            // Keep the first (preferred) event
            let preferred_event = events_with_uid.into_iter().next().unwrap();
            println!("🔄 UID dedup: Keeping '{}' (RRULE: {})",
                preferred_event.summary.as_ref().unwrap_or(&"No Title".to_string()),
                if preferred_event.rrule.is_some() { "Yes" } else { "No" }
            );
            uid_deduplicated_events.push(preferred_event);
        }
    }
    
    // Second pass: separate recurring and single events from UID-deduplicated set
    let mut recurring_events = Vec::new();
    let mut single_events = Vec::new();
    
    for event in uid_deduplicated_events.drain(..) {
        if event.rrule.is_some() {
            recurring_events.push(event);
        } else {
            single_events.push(event);
        }
    }
    
    // Third pass: Group recurring events by normalized title and consolidate different RRULE patterns
    let mut title_groups: HashMap<String, Vec<VEvent>> = HashMap::new();
    
    for event in recurring_events.drain(..) {
        let title = normalize_title(event.summary.as_ref().unwrap_or(&String::new()));
        title_groups.entry(title).or_insert_with(Vec::new).push(event);
    }
    
    let mut deduplicated_recurring = Vec::new();
    
    for (title, events_with_title) in title_groups.drain() {
        if events_with_title.len() == 1 {
            // Single event with this title, keep as-is
            deduplicated_recurring.push(events_with_title.into_iter().next().unwrap());
        } else {
            // Multiple events with same title - consolidate or deduplicate
            println!("🔍 Found {} events with title '{}'", events_with_title.len(), title);
            
            // Check if these are actually different recurring patterns for the same logical event
            let consolidated = consolidate_same_title_events(events_with_title);
            deduplicated_recurring.extend(consolidated);
        }
    }
    
    // Fourth pass: filter single events, removing those that would be generated by recurring events
    let mut deduplicated_single = Vec::new();
    let mut seen_single: HashMap<String, usize> = HashMap::new();
    
    for event in single_events.drain(..) {
        let normalized_title = normalize_title(event.summary.as_ref().unwrap_or(&String::new()));
        let dedup_key = format!(
            "{}|{}", 
            event.dtstart.format("%Y%m%dT%H%M%S"),
            normalized_title
        );
        
        // First check for exact duplicates among single events
        if let Some(&existing_index) = seen_single.get(&dedup_key) {
            let existing_event: &VEvent = &deduplicated_single[existing_index];
            let current_completeness = event_completeness_score(&event);
            let existing_completeness = event_completeness_score(existing_event);
            
            if current_completeness > existing_completeness {
                println!("🔄 Replacing single event: Keeping '{}' over '{}'",
                    event.summary.as_ref().unwrap_or(&"No Title".to_string()),
                    existing_event.summary.as_ref().unwrap_or(&"No Title".to_string())
                );
                deduplicated_single[existing_index] = event;
            } else {
                println!("🚫 Discarding duplicate single event: Keeping existing '{}'",
                    existing_event.summary.as_ref().unwrap_or(&"No Title".to_string())
                );
            }
            continue;
        }
        
        // Check if this single event would be generated by any recurring event
        let is_rrule_generated = deduplicated_recurring.iter().any(|recurring_event| {
            // Check if this single event matches the recurring event's pattern (use normalized titles)
            let single_title = normalize_title(event.summary.as_ref().unwrap_or(&String::new()));
            let recurring_title = normalize_title(recurring_event.summary.as_ref().unwrap_or(&String::new()));
            
            if single_title != recurring_title {
                return false; // Different events
            }
            
            // Check if this single event would be generated by the recurring event
            would_event_be_generated_by_rrule(recurring_event, &event)
        });
        
        if is_rrule_generated {
            println!("🚫 Discarding RRULE-generated instance: '{}' at {} would be generated by recurring event",
                event.summary.as_ref().unwrap_or(&"No Title".to_string()),
                event.dtstart.format("%Y-%m-%d %H:%M")
            );
        } else {
            // This is a unique single event
            seen_single.insert(dedup_key, deduplicated_single.len());
            deduplicated_single.push(event);
        }
    }
    
    // Combine recurring and single events
    let mut result = deduplicated_recurring;
    result.extend(deduplicated_single);
    
    println!("📊 Deduplication complete: {} -> {} events ({} recurring, {} single)", 
        original_count, result.len(), 
        result.iter().filter(|e| e.rrule.is_some()).count(),
        result.iter().filter(|e| e.rrule.is_none()).count()
    );
    
    result
}

/// Normalize title for grouping similar events
fn normalize_title(title: &str) -> String {
    title.trim()
        .to_lowercase()
        .chars()
        .filter(|c| c.is_alphanumeric() || c.is_whitespace())
        .collect::<String>()
        .split_whitespace()
        .collect::<Vec<&str>>()
        .join(" ")
}

/// Consolidate events with the same title but potentially different RRULE patterns
/// This handles cases where calendar systems provide multiple recurring definitions
/// for the same logical meeting (e.g., one RRULE for Tuesdays, another for Thursdays)
fn consolidate_same_title_events(events: Vec<VEvent>) -> Vec<VEvent> {
    if events.is_empty() {
        return events;
    }
    
    // Log the RRULEs we're working with
    for event in &events {
        if let Some(rrule) = &event.rrule {
            println!("🔍 RRULE for '{}': {}", 
                event.summary.as_ref().unwrap_or(&"No Title".to_string()),
                rrule
            );
        }
    }
    
    // Check if all events have similar time patterns and could be consolidated
    let first_event = &events[0];
    let base_time = first_event.dtstart.time();
    let base_duration = if let Some(end) = first_event.dtend {
        Some(end.signed_duration_since(first_event.dtstart))
    } else {
        None
    };
    
    // Check if all events have the same time and duration
    let can_consolidate = events.iter().all(|event| {
        let same_time = event.dtstart.time() == base_time;
        let same_duration = match (event.dtend, base_duration) {
            (Some(end), Some(base_dur)) => end.signed_duration_since(event.dtstart) == base_dur,
            (None, None) => true,
            _ => false,
        };
        same_time && same_duration
    });
    
    if !can_consolidate {
        println!("🚫 Cannot consolidate events - different times or durations");
        // Just deduplicate exact duplicates
        return deduplicate_exact_recurring_events(events);
    }
    
    // Try to detect if these are complementary weekly patterns
    let weekly_events: Vec<_> = events.iter()
        .filter(|e| e.rrule.as_ref().map_or(false, |r| r.contains("FREQ=WEEKLY")))
        .collect();
    
    if weekly_events.len() >= 2 && weekly_events.len() == events.len() {
        // All events are weekly - try to consolidate into a single multi-day weekly pattern
        if let Some(consolidated) = consolidate_weekly_patterns(&events) {
            println!("✅ Successfully consolidated {} weekly patterns into one", events.len());
            return vec![consolidated];
        }
    }
    
    // If we can't consolidate, just deduplicate exact matches and keep the most complete one
    println!("🚫 Cannot consolidate - keeping most complete event");
    let deduplicated = deduplicate_exact_recurring_events(events);
    
    // If we still have multiple events, keep only the most complete one
    if deduplicated.len() > 1 {
        let best_event = deduplicated.into_iter()
            .max_by_key(|e| event_completeness_score(e))
            .unwrap();
        
        println!("🎯 Kept most complete event: '{}'", 
            best_event.summary.as_ref().unwrap_or(&"No Title".to_string())
        );
        vec![best_event]
    } else {
        deduplicated
    }
}

/// Deduplicate exact recurring event matches
fn deduplicate_exact_recurring_events(events: Vec<VEvent>) -> Vec<VEvent> {
    use std::collections::HashMap;
    
    let mut seen: HashMap<String, usize> = HashMap::new();
    let mut deduplicated = Vec::new();
    
    for event in events {
        let dedup_key = format!(
            "{}|{}|{}", 
            event.dtstart.format("%Y%m%dT%H%M%S"),
            event.summary.as_ref().unwrap_or(&String::new()),
            event.rrule.as_ref().unwrap_or(&String::new())
        );
        
        if let Some(&existing_index) = seen.get(&dedup_key) {
            let existing_event: &VEvent = &deduplicated[existing_index];
            let current_completeness = event_completeness_score(&event);
            let existing_completeness = event_completeness_score(existing_event);
            
            if current_completeness > existing_completeness {
                println!("🔄 Replacing exact duplicate: Keeping more complete event");
                deduplicated[existing_index] = event;
            }
        } else {
            seen.insert(dedup_key, deduplicated.len());
            deduplicated.push(event);
        }
    }
    
    deduplicated
}

/// Attempt to consolidate multiple weekly RRULE patterns into a single pattern
fn consolidate_weekly_patterns(events: &[VEvent]) -> Option<VEvent> {
    use std::collections::HashSet;
    
    let mut all_days = HashSet::new();
    let mut base_event = None;
    
    for event in events {
        let Some(rrule) = &event.rrule else { continue; };
        
        if !rrule.contains("FREQ=WEEKLY") {
            continue;
        }
        
        // Extract BYDAY if present
        if let Some(byday_part) = rrule.split(';').find(|part| part.starts_with("BYDAY=")) {
            let days_str = byday_part.strip_prefix("BYDAY=").unwrap_or("");
            for day in days_str.split(',') {
                all_days.insert(day.trim().to_string());
            }
        } else {
            // If no BYDAY specified, use the weekday from the start date
            let weekday = match event.dtstart.weekday() {
                chrono::Weekday::Mon => "MO",
                chrono::Weekday::Tue => "TU", 
                chrono::Weekday::Wed => "WE",
                chrono::Weekday::Thu => "TH",
                chrono::Weekday::Fri => "FR",
                chrono::Weekday::Sat => "SA",
                chrono::Weekday::Sun => "SU",
            };
            all_days.insert(weekday.to_string());
        }
        
        // Use the first event as the base (we already know they have same time/duration)
        if base_event.is_none() {
            base_event = Some(event.clone());
        }
    }
    
    if all_days.is_empty() || base_event.is_none() {
        return None;
    }
    
    // Create consolidated RRULE
    let mut base = base_event.unwrap();
    let days_list: Vec<_> = all_days.into_iter().collect();
    let byday_str = days_list.join(",");
    
    // Build new RRULE with consolidated BYDAY
    let new_rrule = if let Some(existing_rrule) = &base.rrule {
        // Remove existing BYDAY and add our consolidated one
        let parts: Vec<_> = existing_rrule.split(';')
            .filter(|part| !part.starts_with("BYDAY="))
            .collect();
        format!("{};BYDAY={}", parts.join(";"), byday_str)
    } else {
        format!("FREQ=WEEKLY;BYDAY={}", byday_str)
    };
    
    base.rrule = Some(new_rrule);
    
    println!("🔗 Consolidated weekly pattern: BYDAY={}", byday_str);
    Some(base)
}

/// Check if a single event would be generated by a recurring event's RRULE
fn would_event_be_generated_by_rrule(recurring_event: &VEvent, single_event: &VEvent) -> bool {
    let Some(rrule) = &recurring_event.rrule else {
        return false; // No RRULE to check against
    };
    
    // Parse basic RRULE patterns
    if rrule.contains("FREQ=DAILY") {
        // Daily recurrence
        let interval = extract_interval_from_rrule(rrule).unwrap_or(1);
        let days_diff = (single_event.dtstart.date() - recurring_event.dtstart.date()).num_days();
        
        if days_diff >= 0 && days_diff % interval as i64 == 0 {
            // Check if times match (allowing for timezone differences within same day)
            let recurring_time = recurring_event.dtstart.time();
            let single_time = single_event.dtstart.time();
            return recurring_time == single_time;
        }
    } else if rrule.contains("FREQ=WEEKLY") {
        // Weekly recurrence
        let interval = extract_interval_from_rrule(rrule).unwrap_or(1);
        let days_diff = (single_event.dtstart.date() - recurring_event.dtstart.date()).num_days();
        
        // First check if it's the same day of week and time
        let recurring_weekday = recurring_event.dtstart.weekday();
        let single_weekday = single_event.dtstart.weekday();
        let recurring_time = recurring_event.dtstart.time();
        let single_time = single_event.dtstart.time();
        
        if recurring_weekday == single_weekday && recurring_time == single_time && days_diff >= 0 {
            // Calculate how many weeks apart they are
            let weeks_diff = days_diff / 7;
            // Check if this falls on an interval boundary
            return weeks_diff % interval as i64 == 0;
        }
    } else if rrule.contains("FREQ=MONTHLY") {
        // Monthly recurrence - simplified check
        let months_diff = (single_event.dtstart.year() - recurring_event.dtstart.year()) * 12 
            + (single_event.dtstart.month() as i32 - recurring_event.dtstart.month() as i32);
        
        if months_diff >= 0 {
            let interval = extract_interval_from_rrule(rrule).unwrap_or(1) as i32;
            if months_diff % interval == 0 {
                // Same day of month and time
                return recurring_event.dtstart.day() == single_event.dtstart.day()
                    && recurring_event.dtstart.time() == single_event.dtstart.time();
            }
        }
    }
    
    false
}

/// Extract INTERVAL value from RRULE string, defaulting to 1 if not found
fn extract_interval_from_rrule(rrule: &str) -> Option<u32> {
    for part in rrule.split(';') {
        if part.starts_with("INTERVAL=") {
            return part.strip_prefix("INTERVAL=")
                .and_then(|s| s.parse().ok());
        }
    }
    Some(1) // Default interval is 1 if not specified
}

/// Calculate a completeness score for an event based on how many optional fields are filled
fn event_completeness_score(event: &VEvent) -> u32 {
    let mut score = 0;
    
    if event.summary.is_some() { score += 1; }
    if event.description.is_some() { score += 1; }
    if event.location.is_some() { score += 1; }
    if event.dtend.is_some() { score += 1; }
    if event.rrule.is_some() { score += 1; }
    if !event.categories.is_empty() { score += 1; }
    if !event.alarms.is_empty() { score += 1; }
    if event.organizer.is_some() { score += 1; }
    if !event.attendees.is_empty() { score += 1; }
    
    score
}