use std::sync::Arc;
use async_trait::async_trait;
use chrono::{DateTime, Utc};

use crate::application::dtos::calendar_dto::{
    CalendarDto, CalendarEventDto, CreateCalendarDto, UpdateCalendarDto,
    CreateEventDto, UpdateEventDto, CreateEventICalDto
};
use crate::application::ports::calendar_ports::{CalendarStoragePort, CalendarUseCase};
use crate::common::errors::{DomainError, ErrorKind};

pub struct CalendarService {
    calendar_storage: Arc<dyn CalendarStoragePort>,
}

impl CalendarService {
    pub fn new(calendar_storage: Arc<dyn CalendarStoragePort>) -> Self {
        Self {
            calendar_storage,
        }
    }
}

#[async_trait]
impl CalendarUseCase for CalendarService {
    async fn create_calendar(&self, calendar: CreateCalendarDto) -> Result<CalendarDto, DomainError> {
        // This function requires the current user context which will come from middleware
        // For now, we'll use a dummy implementation that needs to be completed
        
        // In a real implementation, get user_id from current user context
        let user_id = "current_user_id";  // This should come from middleware
        
        self.calendar_storage.create_calendar(calendar, user_id).await
    }
    
    async fn update_calendar(&self, calendar_id: &str, update: UpdateCalendarDto) -> Result<CalendarDto, DomainError> {
        // In a real implementation, we would:
        // 1. Get the current user ID from middleware
        // 2. Verify that the user has access to this calendar
        // 3. Update the calendar if they have permission
        
        let user_id = "current_user_id";  // This should come from middleware
        
        // Check if user has access
        let has_access = self.calendar_storage.check_calendar_access(calendar_id, user_id).await?;
        
        if !has_access {
            return Err(DomainError::new(
                ErrorKind::AccessDenied,
                "Calendar",
                "You don't have permission to update this calendar"
            ));
        }
        
        self.calendar_storage.update_calendar(calendar_id, update).await
    }
    
    async fn delete_calendar(&self, calendar_id: &str) -> Result<(), DomainError> {
        let user_id = "current_user_id";  // This should come from middleware
        
        // Check if user has access
        let has_access = self.calendar_storage.check_calendar_access(calendar_id, user_id).await?;
        
        if !has_access {
            return Err(DomainError::new(
                ErrorKind::AccessDenied,
                "Calendar",
                "You don't have permission to delete this calendar"
            ));
        }
        
        self.calendar_storage.delete_calendar(calendar_id).await
    }
    
    async fn get_calendar(&self, calendar_id: &str) -> Result<CalendarDto, DomainError> {
        let user_id = "current_user_id";  // This should come from middleware
        
        // Get the calendar
        let calendar = self.calendar_storage.get_calendar(calendar_id).await?;
        
        // Check if user has access or if calendar is public
        let has_access = self.calendar_storage.check_calendar_access(calendar_id, user_id).await?;
        
        if !has_access && !calendar.is_public {
            return Err(DomainError::new(
                ErrorKind::AccessDenied,
                "Calendar",
                "You don't have permission to view this calendar"
            ));
        }
        
        Ok(calendar)
    }
    
    async fn list_my_calendars(&self) -> Result<Vec<CalendarDto>, DomainError> {
        let user_id = "current_user_id";  // This should come from middleware
        
        self.calendar_storage.list_calendars_by_owner(user_id).await
    }
    
    async fn list_shared_calendars(&self) -> Result<Vec<CalendarDto>, DomainError> {
        let user_id = "current_user_id";  // This should come from middleware
        
        self.calendar_storage.list_calendars_shared_with_user(user_id).await
    }
    
    async fn list_public_calendars(&self, limit: Option<i64>, offset: Option<i64>) -> Result<Vec<CalendarDto>, DomainError> {
        let limit = limit.unwrap_or(100);
        let offset = offset.unwrap_or(0);
        
        self.calendar_storage.list_public_calendars(limit, offset).await
    }
    
    async fn share_calendar(&self, calendar_id: &str, user_id: &str, access_level: &str) -> Result<(), DomainError> {
        let current_user_id = "current_user_id";  // This should come from middleware
        
        // Check if current user has access
        let calendar = self.calendar_storage.get_calendar(calendar_id).await?;
        
        // Only the owner can share the calendar
        if calendar.owner_id != current_user_id {
            return Err(DomainError::new(
                ErrorKind::AccessDenied,
                "Calendar",
                "Only the calendar owner can change sharing settings"
            ));
        }
        
        // Validate access_level
        match access_level {
            "read" | "write" | "owner" => {},
            _ => return Err(DomainError::new(
                ErrorKind::InvalidInput,
                "Calendar",
                format!("Invalid access level: {}. Valid values are: read, write, owner", access_level)
            )),
        }
        
        self.calendar_storage.share_calendar(calendar_id, user_id, access_level).await
    }
    
    async fn remove_calendar_sharing(&self, calendar_id: &str, user_id: &str) -> Result<(), DomainError> {
        let current_user_id = "current_user_id";  // This should come from middleware
        
        // Check if current user has access
        let calendar = self.calendar_storage.get_calendar(calendar_id).await?;
        
        // Only the owner can change sharing settings
        if calendar.owner_id != current_user_id {
            return Err(DomainError::new(
                ErrorKind::AccessDenied,
                "Calendar",
                "Only the calendar owner can change sharing settings"
            ));
        }
        
        self.calendar_storage.remove_calendar_sharing(calendar_id, user_id).await
    }
    
    async fn get_calendar_shares(&self, calendar_id: &str) -> Result<Vec<(String, String)>, DomainError> {
        let current_user_id = "current_user_id";  // This should come from middleware
        
        // Check if current user has access
        let calendar = self.calendar_storage.get_calendar(calendar_id).await?;
        
        // Only the owner can view sharing settings
        if calendar.owner_id != current_user_id {
            return Err(DomainError::new(
                ErrorKind::AccessDenied,
                "Calendar",
                "Only the calendar owner can view sharing settings"
            ));
        }
        
        self.calendar_storage.get_calendar_shares(calendar_id).await
    }
    
    async fn create_event(&self, event: CreateEventDto) -> Result<CalendarEventDto, DomainError> {
        let user_id = "current_user_id";  // This should come from middleware
        
        // Check if user has access to the calendar
        let has_access = self.calendar_storage.check_calendar_access(&event.calendar_id, user_id).await?;
        
        if !has_access {
            return Err(DomainError::new(
                ErrorKind::AccessDenied,
                "Calendar",
                "You don't have permission to add events to this calendar"
            ));
        }
        
        self.calendar_storage.create_event(event).await
    }
    
    async fn create_event_from_ical(&self, event: CreateEventICalDto) -> Result<CalendarEventDto, DomainError> {
        let user_id = "current_user_id";  // This should come from middleware
        
        // Check if user has access to the calendar
        let has_access = self.calendar_storage.check_calendar_access(&event.calendar_id, user_id).await?;
        
        if !has_access {
            return Err(DomainError::new(
                ErrorKind::AccessDenied,
                "Calendar",
                "You don't have permission to add events to this calendar"
            ));
        }
        
        self.calendar_storage.create_event_from_ical(event).await
    }
    
    async fn update_event(&self, event_id: &str, update: UpdateEventDto) -> Result<CalendarEventDto, DomainError> {
        let user_id = "current_user_id";  // This should come from middleware
        
        // Get the event to find its calendar
        let event = self.calendar_storage.get_event(event_id).await?;
        
        // Check if user has access to the calendar
        let has_access = self.calendar_storage.check_calendar_access(&event.calendar_id, user_id).await?;
        
        if !has_access {
            return Err(DomainError::new(
                ErrorKind::AccessDenied,
                "Calendar",
                "You don't have permission to update events in this calendar"
            ));
        }
        
        self.calendar_storage.update_event(event_id, update).await
    }
    
    async fn delete_event(&self, event_id: &str) -> Result<(), DomainError> {
        let user_id = "current_user_id";  // This should come from middleware
        
        // Get the event to find its calendar
        let event = self.calendar_storage.get_event(event_id).await?;
        
        // Check if user has access to the calendar
        let has_access = self.calendar_storage.check_calendar_access(&event.calendar_id, user_id).await?;
        
        if !has_access {
            return Err(DomainError::new(
                ErrorKind::AccessDenied,
                "Calendar",
                "You don't have permission to delete events in this calendar"
            ));
        }
        
        self.calendar_storage.delete_event(event_id).await
    }
    
    async fn get_event(&self, event_id: &str) -> Result<CalendarEventDto, DomainError> {
        let user_id = "current_user_id";  // This should come from middleware
        
        // Get the event
        let event = self.calendar_storage.get_event(event_id).await?;
        
        // Check if user has access to the calendar
        let has_access = self.calendar_storage.check_calendar_access(&event.calendar_id, user_id).await?;
        
        // Check if calendar is public
        let calendar = self.calendar_storage.get_calendar(&event.calendar_id).await?;
        
        if !has_access && !calendar.is_public {
            return Err(DomainError::new(
                ErrorKind::AccessDenied,
                "Calendar",
                "You don't have permission to view events in this calendar"
            ));
        }
        
        Ok(event)
    }
    
    async fn list_events(&self, calendar_id: &str, limit: Option<i64>, offset: Option<i64>) -> Result<Vec<CalendarEventDto>, DomainError> {
        let user_id = "current_user_id";  // This should come from middleware
        
        // Check if user has access to the calendar
        let has_access = self.calendar_storage.check_calendar_access(calendar_id, user_id).await?;
        
        // Check if calendar is public
        let calendar = self.calendar_storage.get_calendar(calendar_id).await?;
        
        if !has_access && !calendar.is_public {
            return Err(DomainError::new(
                ErrorKind::AccessDenied,
                "Calendar",
                "You don't have permission to view events in this calendar"
            ));
        }
        
        // Use pagination if provided
        if limit.is_some() || offset.is_some() {
            let limit = limit.unwrap_or(100);
            let offset = offset.unwrap_or(0);
            
            self.calendar_storage.list_events_by_calendar_paginated(calendar_id, limit, offset).await
        } else {
            self.calendar_storage.list_events_by_calendar(calendar_id).await
        }
    }
    
    async fn get_events_in_range(
        &self, 
        calendar_id: &str, 
        start: DateTime<Utc>, 
        end: DateTime<Utc>
    ) -> Result<Vec<CalendarEventDto>, DomainError> {
        let user_id = "current_user_id";  // This should come from middleware
        
        // Check if user has access to the calendar
        let has_access = self.calendar_storage.check_calendar_access(calendar_id, user_id).await?;
        
        // Check if calendar is public
        let calendar = self.calendar_storage.get_calendar(calendar_id).await?;
        
        if !has_access && !calendar.is_public {
            return Err(DomainError::new(
                ErrorKind::AccessDenied,
                "Calendar",
                "You don't have permission to view events in this calendar"
            ));
        }
        
        self.calendar_storage.get_events_in_time_range(calendar_id, &start, &end).await
    }
    
    // ─── User-contextualized variants (for CalDAV protocol handler) ──
    
    async fn create_calendar_for_user(&self, calendar: CreateCalendarDto, user_id: &str) -> Result<CalendarDto, DomainError> {
        self.calendar_storage.create_calendar(calendar, user_id).await
    }
    
    async fn update_calendar_for_user(&self, calendar_id: &str, update: UpdateCalendarDto, user_id: &str) -> Result<CalendarDto, DomainError> {
        let has_access = self.calendar_storage.check_calendar_access(calendar_id, user_id).await?;
        if !has_access {
            return Err(DomainError::new(ErrorKind::AccessDenied, "Calendar", "You don't have permission to update this calendar"));
        }
        self.calendar_storage.update_calendar(calendar_id, update).await
    }
    
    async fn delete_calendar_for_user(&self, calendar_id: &str, user_id: &str) -> Result<(), DomainError> {
        let has_access = self.calendar_storage.check_calendar_access(calendar_id, user_id).await?;
        if !has_access {
            return Err(DomainError::new(ErrorKind::AccessDenied, "Calendar", "You don't have permission to delete this calendar"));
        }
        self.calendar_storage.delete_calendar(calendar_id).await
    }
    
    async fn get_calendar_for_user(&self, calendar_id: &str, user_id: &str) -> Result<CalendarDto, DomainError> {
        let calendar = self.calendar_storage.get_calendar(calendar_id).await?;
        let has_access = self.calendar_storage.check_calendar_access(calendar_id, user_id).await?;
        if !has_access && !calendar.is_public {
            return Err(DomainError::new(ErrorKind::AccessDenied, "Calendar", "You don't have permission to view this calendar"));
        }
        Ok(calendar)
    }
    
    async fn list_my_calendars_for_user(&self, user_id: &str) -> Result<Vec<CalendarDto>, DomainError> {
        self.calendar_storage.list_calendars_by_owner(user_id).await
    }
    
    async fn list_events_for_user(&self, calendar_id: &str, limit: Option<i64>, offset: Option<i64>, user_id: &str) -> Result<Vec<CalendarEventDto>, DomainError> {
        let has_access = self.calendar_storage.check_calendar_access(calendar_id, user_id).await?;
        let calendar = self.calendar_storage.get_calendar(calendar_id).await?;
        if !has_access && !calendar.is_public {
            return Err(DomainError::new(ErrorKind::AccessDenied, "Calendar", "You don't have permission to view events in this calendar"));
        }
        if limit.is_some() || offset.is_some() {
            let limit = limit.unwrap_or(100);
            let offset = offset.unwrap_or(0);
            self.calendar_storage.list_events_by_calendar_paginated(calendar_id, limit, offset).await
        } else {
            self.calendar_storage.list_events_by_calendar(calendar_id).await
        }
    }
    
    async fn get_events_in_range_for_user(&self, calendar_id: &str, start: DateTime<Utc>, end: DateTime<Utc>, user_id: &str) -> Result<Vec<CalendarEventDto>, DomainError> {
        let has_access = self.calendar_storage.check_calendar_access(calendar_id, user_id).await?;
        let calendar = self.calendar_storage.get_calendar(calendar_id).await?;
        if !has_access && !calendar.is_public {
            return Err(DomainError::new(ErrorKind::AccessDenied, "Calendar", "You don't have permission to view events in this calendar"));
        }
        self.calendar_storage.get_events_in_time_range(calendar_id, &start, &end).await
    }
    
    async fn create_event_from_ical_for_user(&self, event: CreateEventICalDto, user_id: &str) -> Result<CalendarEventDto, DomainError> {
        let has_access = self.calendar_storage.check_calendar_access(&event.calendar_id, user_id).await?;
        if !has_access {
            return Err(DomainError::new(ErrorKind::AccessDenied, "Calendar", "You don't have permission to add events to this calendar"));
        }
        self.calendar_storage.create_event_from_ical(event).await
    }
    
    async fn delete_event_for_user(&self, event_id: &str, user_id: &str) -> Result<(), DomainError> {
        let event = self.calendar_storage.get_event(event_id).await?;
        let has_access = self.calendar_storage.check_calendar_access(&event.calendar_id, user_id).await?;
        if !has_access {
            return Err(DomainError::new(ErrorKind::AccessDenied, "Calendar", "You don't have permission to delete events in this calendar"));
        }
        self.calendar_storage.delete_event(event_id).await
    }
}