//! CouchDB client integration for mail2couch
//! 
//! This module provides a CouchDB client that handles database operations
//! for storing email messages and sync metadata.

use crate::config::CouchDbConfig;
use crate::schemas::{MailDocument, SyncMetadata};
use anyhow::{anyhow, Result};
use reqwest::{Client, StatusCode};
use serde_json::Value;
use std::time::Duration;
use thiserror::Error;

#[derive(Error, Debug)]
pub enum CouchError {
    #[error("HTTP request failed: {0}")]
    Http(#[from] reqwest::Error),
    #[error("CouchDB error: {status} - {message}")]
    CouchDb { status: u16, message: String },
    #[error("Document not found: {id}")]
    NotFound { id: String },
    #[error("Serialization error: {0}")]
    Serialization(#[from] serde_json::Error),
    #[error("Database error: {0}")]
    Database(String),
}

/// CouchDB client for mail2couch operations
pub struct CouchClient {
    client: Client,
    base_url: String,
    auth: Option<(String, String)>,
}

/// Response from CouchDB for document operations
#[derive(Debug, serde::Deserialize)]
pub struct CouchResponse {
    pub ok: Option<bool>,
    pub id: Option<String>,
    pub rev: Option<String>,
    pub error: Option<String>,
    pub reason: Option<String>,
}

impl CouchClient {
    /// Generic retry helper for CouchDB operations
    async fn retry_operation<F, Fut, T>(&self, operation_name: &str, operation: F) -> Result<T>
    where
        F: Fn() -> Fut,
        Fut: std::future::Future<Output = Result<T>>,
    {
        const MAX_RETRIES: u32 = 3;
        const RETRY_DELAY_MS: u64 = 1000;

        let mut last_error = None;

        for attempt in 1..=MAX_RETRIES {
            match operation().await {
                Ok(result) => {
                    if attempt > 1 {
                        log::debug!("✅ CouchDB {} successful on attempt {}", operation_name, attempt);
                    }
                    return Ok(result);
                }
                Err(e) => {
                    // Check if this is a retryable error
                    let is_retryable = match &e.downcast_ref::<CouchError>() {
                        Some(CouchError::Http(_)) => true,  // Network errors are retryable
                        Some(CouchError::CouchDb { status, .. }) => {
                            // Retry on server errors (5xx) but not client errors (4xx)
                            *status >= 500
                        }
                        _ => false, // Other errors are not retryable
                    };

                    last_error = Some(e);
                    
                    if is_retryable && attempt < MAX_RETRIES {
                        log::warn!(
                            "🔄 CouchDB {} attempt {} failed, retrying in {}ms: {}",
                            operation_name,
                            attempt,
                            RETRY_DELAY_MS,
                            last_error.as_ref().unwrap()
                        );
                        tokio::time::sleep(Duration::from_millis(RETRY_DELAY_MS)).await;
                    } else {
                        break;
                    }
                }
            }
        }

        Err(anyhow!(
            "CouchDB {} failed after {} attempts. Last error: {}",
            operation_name,
            MAX_RETRIES,
            last_error.unwrap()
        ))
    }

    /// Create a new CouchDB client
    pub fn new(config: &CouchDbConfig) -> Result<Self> {
        let client = Client::new();
        let base_url = config.url.trim_end_matches('/').to_string();
        let auth = if !config.user.is_empty() {
            Some((config.user.clone(), config.password.clone()))
        } else {
            None
        };

        Ok(CouchClient {
            client,
            base_url,
            auth,
        })
    }

    /// Test connection to CouchDB
    pub async fn test_connection(&self) -> Result<()> {
        let url = format!("{}/", self.base_url);
        let mut request = self.client.get(&url);
        
        if let Some((username, password)) = &self.auth {
            request = request.basic_auth(username, Some(password));
        }

        let response = request.send().await?;
        
        if response.status().is_success() {
            Ok(())
        } else {
            Err(anyhow!("CouchDB connection failed: {}", response.status()))
        }
    }

    /// Create a database if it doesn't exist
    pub async fn create_database(&self, db_name: &str) -> Result<()> {
        // First check if database exists
        if self.database_exists(db_name).await? {
            return Ok(());
        }

        let url = format!("{}/{}", self.base_url, db_name);
        let mut request = self.client.put(&url);
        
        if let Some((username, password)) = &self.auth {
            request = request.basic_auth(username, Some(password));
        }

        let response = request.send().await?;
        
        match response.status() {
            StatusCode::CREATED | StatusCode::ACCEPTED => Ok(()),
            status => {
                let error_text = response.text().await?;
                Err(anyhow!("Failed to create database {}: {} - {}", db_name, status, error_text))
            }
        }
    }

    /// Check if a database exists
    pub async fn database_exists(&self, db_name: &str) -> Result<bool> {
        let url = format!("{}/{}", self.base_url, db_name);
        let mut request = self.client.head(&url);
        
        if let Some((username, password)) = &self.auth {
            request = request.basic_auth(username, Some(password));
        }

        let response = request.send().await?;
        Ok(response.status().is_success())
    }

    /// Store a mail document in CouchDB with optional attachments and retry logic
    pub async fn store_mail_document(&self, db_name: &str, mut document: MailDocument) -> Result<String> {
        // Set the document ID if not already set
        if document.id.is_none() {
            document.set_id();
        }

        let doc_id = document.id.as_ref().unwrap().clone();
        
        // Check if document already exists to avoid duplicates
        if self.document_exists(db_name, &doc_id).await? {
            return Ok(doc_id);
        }

        self.retry_operation("store_mail_document", || async {
            let url = format!("{}/{}/{}", self.base_url, db_name, doc_id);
            let mut request = self.client.put(&url).json(&document);
            
            if let Some((username, password)) = &self.auth {
                request = request.basic_auth(username, Some(password));
            }

            let response = request.send().await
                .map_err(|e| CouchError::Http(e))?;
            
            match response.status() {
                StatusCode::CREATED | StatusCode::ACCEPTED => {
                    let couch_response: CouchResponse = response.json().await
                        .map_err(|e| CouchError::Http(e))?;
                    Ok(couch_response.id.unwrap_or_else(|| doc_id.clone()))
                }
                status => {
                    let error_text = response.text().await
                        .unwrap_or_else(|_| "Failed to read error response".to_string());
                    Err(CouchError::CouchDb {
                        status: status.as_u16(),
                        message: error_text,
                    }.into())
                }
            }
        }).await
    }

    /// Store an attachment for a document in CouchDB
    pub async fn store_attachment(
        &self,
        db_name: &str,
        doc_id: &str,
        attachment_name: &str,
        content_type: &str,
        data: &[u8],
    ) -> Result<String> {
        // First get the current document revision
        let doc_response = self.get_document_rev(db_name, doc_id).await?;
        let rev = doc_response.ok_or_else(|| anyhow!("Document {} not found", doc_id))?;

        // Upload the attachment
        let url = format!("{}/{}/{}/{}?rev={}", self.base_url, db_name, doc_id, attachment_name, rev);
        let mut request = self.client
            .put(&url)
            .header("Content-Type", content_type)
            .body(data.to_vec());
        
        if let Some((username, password)) = &self.auth {
            request = request.basic_auth(username, Some(password));
        }

        let response = request.send().await?;
        
        match response.status() {
            StatusCode::CREATED | StatusCode::ACCEPTED => {
                let couch_response: CouchResponse = response.json().await?;
                Ok(couch_response.rev.unwrap_or_else(|| rev))
            }
            status => {
                let error_text = response.text().await?;
                Err(anyhow!("Failed to store attachment {}: {} - {}", attachment_name, status, error_text))
            }
        }
    }

    /// Get document revision
    async fn get_document_rev(&self, db_name: &str, doc_id: &str) -> Result<Option<String>> {
        let url = format!("{}/{}/{}", self.base_url, db_name, doc_id);
        let mut request = self.client.get(&url);
        
        if let Some((username, password)) = &self.auth {
            request = request.basic_auth(username, Some(password));
        }

        let response = request.send().await?;
        
        match response.status() {
            StatusCode::OK => {
                let doc: Value = response.json().await?;
                Ok(doc["_rev"].as_str().map(|s| s.to_string()))
            }
            StatusCode::NOT_FOUND => Ok(None),
            status => {
                let error_text = response.text().await?;
                Err(anyhow!("Failed to get document {}: {} - {}", doc_id, status, error_text))
            }
        }
    }

    /// Store sync metadata in CouchDB
    pub async fn store_sync_metadata(&self, db_name: &str, metadata: &SyncMetadata) -> Result<String> {
        let doc_id = metadata.id.as_ref().unwrap();
        
        // Try to get existing document first to get the revision
        let mut metadata_to_store = metadata.clone();
        if let Ok(existing) = self.get_sync_metadata(db_name, &metadata.mailbox).await {
            metadata_to_store.rev = existing.rev;
        }

        let url = format!("{}/{}/{}", self.base_url, db_name, doc_id);
        let mut request = self.client.put(&url).json(&metadata_to_store);
        
        if let Some((username, password)) = &self.auth {
            request = request.basic_auth(username, Some(password));
        }

        let response = request.send().await?;
        
        match response.status() {
            StatusCode::CREATED | StatusCode::ACCEPTED => {
                let couch_response: CouchResponse = response.json().await?;
                Ok(couch_response.id.unwrap_or_else(|| doc_id.clone()))
            }
            status => {
                let error_text = response.text().await?;
                Err(anyhow!("Failed to store sync metadata {}: {} - {}", doc_id, status, error_text))
            }
        }
    }

    /// Get sync metadata for a mailbox
    pub async fn get_sync_metadata(&self, db_name: &str, mailbox: &str) -> Result<SyncMetadata> {
        let doc_id = format!("sync_metadata_{}", mailbox);
        let url = format!("{}/{}/{}", self.base_url, db_name, doc_id);
        let mut request = self.client.get(&url);
        
        if let Some((username, password)) = &self.auth {
            request = request.basic_auth(username, Some(password));
        }

        let response = request.send().await?;
        
        match response.status() {
            StatusCode::OK => {
                let metadata: SyncMetadata = response.json().await?;
                Ok(metadata)
            }
            StatusCode::NOT_FOUND => {
                Err(CouchError::NotFound { id: doc_id }.into())
            }
            status => {
                let error_text = response.text().await?;
                Err(anyhow!("Failed to get sync metadata {}: {} - {}", doc_id, status, error_text))
            }
        }
    }

    /// Check if a document exists
    pub async fn document_exists(&self, db_name: &str, doc_id: &str) -> Result<bool> {
        let url = format!("{}/{}/{}", self.base_url, db_name, doc_id);
        let mut request = self.client.head(&url);
        
        if let Some((username, password)) = &self.auth {
            request = request.basic_auth(username, Some(password));
        }

        let response = request.send().await?;
        Ok(response.status() == StatusCode::OK)
    }

    /// Get database information
    pub async fn get_database_info(&self, db_name: &str) -> Result<Value> {
        let url = format!("{}/{}", self.base_url, db_name);
        let mut request = self.client.get(&url);
        
        if let Some((username, password)) = &self.auth {
            request = request.basic_auth(username, Some(password));
        }

        let response = request.send().await?;
        
        match response.status() {
            StatusCode::OK => {
                let info: Value = response.json().await?;
                Ok(info)
            }
            status => {
                let error_text = response.text().await?;
                Err(anyhow!("Failed to get database info for {}: {} - {}", db_name, status, error_text))
            }
        }
    }

    /// Get all message UIDs for a specific mailbox from CouchDB
    pub async fn get_mailbox_uids(&self, db_name: &str, mailbox: &str) -> Result<Vec<u32>> {
        let url = format!("{}/{}/_all_docs", self.base_url, db_name);
        let query_params = [
            ("startkey", format!("\"{}\"", mailbox)),
            ("endkey", format!("\"{}\\ufff0\"", mailbox)), // High Unicode character for range end
            ("include_docs", "false".to_string()),
        ];

        let mut request = self.client.get(&url).query(&query_params);
        
        if let Some((username, password)) = &self.auth {
            request = request.basic_auth(username, Some(password));
        }

        let response = request.send().await?;
        
        if !response.status().is_success() {
            return Err(anyhow!("Failed to query stored messages: {}", response.status()));
        }

        let result: serde_json::Value = response.json().await?;
        let mut uids = Vec::new();

        if let Some(rows) = result["rows"].as_array() {
            for row in rows {
                if let Some(id) = row["id"].as_str() {
                    // Parse UID from document ID format: {mailbox}_{uid}
                    if let Some(uid_str) = id.strip_prefix(&format!("{}_", mailbox)) {
                        if let Ok(uid) = uid_str.parse::<u32>() {
                            uids.push(uid);
                        }
                    }
                }
            }
        }

        Ok(uids)
    }

    /// Delete a document (used in sync mode for deleted messages)
    pub async fn delete_document(&self, db_name: &str, doc_id: &str) -> Result<()> {
        // First get the document to get its revision
        let url = format!("{}/{}/{}", self.base_url, db_name, doc_id);
        let mut request = self.client.get(&url);
        
        if let Some((username, password)) = &self.auth {
            request = request.basic_auth(username, Some(password));
        }

        let response = request.send().await?;
        
        if response.status() == StatusCode::NOT_FOUND {
            return Ok(()); // Document already doesn't exist
        }

        let doc: Value = response.json().await?;
        let rev = doc["_rev"].as_str()
            .ok_or_else(|| anyhow!("Document {} has no _rev field", doc_id))?;

        // Now delete the document
        let delete_url = format!("{}/{}/{}?rev={}", self.base_url, db_name, doc_id, rev);
        let mut delete_request = self.client.delete(&delete_url);
        
        if let Some((username, password)) = &self.auth {
            delete_request = delete_request.basic_auth(username, Some(password));
        }

        let delete_response = delete_request.send().await?;
        
        match delete_response.status() {
            StatusCode::OK | StatusCode::ACCEPTED => Ok(()),
            status => {
                let error_text = delete_response.text().await?;
                Err(anyhow!("Failed to delete document {}: {} - {}", doc_id, status, error_text))
            }
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::config::CouchDbConfig;

    fn test_config() -> CouchDbConfig {
        CouchDbConfig {
            url: "http://localhost:5984".to_string(),
            user: "admin".to_string(),
            password: "password".to_string(),
        }
    }

    #[tokio::test]
    async fn test_client_creation() {
        let config = test_config();
        let client = CouchClient::new(&config);
        assert!(client.is_ok());
    }

    // Note: Additional integration tests would require a running CouchDB instance
    // These would be similar to the Go implementation tests
}