icepick 0.1.0

//! FileIO implementation using OpenDAL
//! Compatible with both WASM and native targets

use crate::error::{Error, Result};
use opendal::Operator;
use std::collections::HashMap;
use std::sync::{Arc, RwLock};

/// AWS credentials for creating S3 operators dynamically
#[derive(Clone)]
pub struct AwsCredentials {
    pub access_key_id: String,
    pub secret_access_key: String,
    pub session_token: Option<String>,
}

/// File I/O abstraction for reading/writing Iceberg files
///
/// Supports two modes:
/// - Single operator mode (R2): Uses pre-configured default_operator
/// - Multi-bucket mode (S3 Tables): Creates operators dynamically per bucket using credentials
///
/// For S3 Tables, all buckets are in the same region, so we only cache by bucket name.
#[derive(Clone)]
pub struct FileIO {
    /// AWS credentials for creating operators (S3 Tables mode)
    credentials: Option<AwsCredentials>,
    /// Default region for all operators
    default_region: String,
    /// Cache of operators per bucket (all same region for S3 Tables)
    operator_cache: Arc<RwLock<HashMap<String, Operator>>>,
    /// Pre-configured operator (R2 mode)
    default_operator: Option<Operator>,
}

impl FileIO {
    /// Create a new FileIO with the given OpenDAL operator (R2 mode)
    ///
    /// This creates a FileIO that uses a single pre-configured operator for all operations.
    /// Suitable for R2 and other single-bucket scenarios.
    pub fn new(operator: Operator) -> Self {
        Self {
            credentials: None,
            default_region: String::new(),
            operator_cache: Arc::new(RwLock::new(HashMap::new())),
            default_operator: Some(operator),
        }
    }

    /// Create a new FileIO from AWS credentials (S3 Tables mode)
    ///
    /// This creates a FileIO that dynamically creates and caches operators per bucket.
    /// Suitable for S3 Tables where data may be in different buckets/regions.
    pub fn from_aws_credentials(credentials: AwsCredentials, default_region: String) -> Self {
        Self {
            credentials: Some(credentials),
            default_region,
            operator_cache: Arc::new(RwLock::new(HashMap::new())),
            default_operator: None,
        }
    }

    /// Extract bucket name from S3 URI
    ///
    /// Converts "s3://bucket/path/to/file" to ("bucket", "path/to/file")
    fn extract_bucket_from_uri(&self, path: &str) -> Result<(String, String)> {
        if let Some(stripped) = path.strip_prefix("s3://") {
            if let Some(slash_pos) = stripped.find('/') {
                let bucket = stripped[..slash_pos].to_string();
                let path = stripped[slash_pos + 1..].to_string();
                return Ok((bucket, path));
            } else {
                // Just bucket, no path
                return Ok((stripped.to_string(), String::new()));
            }
        }
        Err(Error::InvalidInput(format!(
            "Path does not start with s3://: {}",
            path
        )))
    }

    /// Get operator for a given path using priority-based routing
    ///
    /// Priority:
    /// 1. If default_operator exists → use it (R2 case)
    /// 2. If credentials exist → create dynamic operator (S3 Tables case)
    /// 3. Error - no operator configured
    async fn get_operator_for_path(&self, path: &str) -> Result<Operator> {
        // Priority 1: Use default operator if available (R2 mode)
        if let Some(ref op) = self.default_operator {
            return Ok(op.clone());
        }

        // Priority 2: Create dynamic operator if credentials available (S3 Tables mode)
        if self.credentials.is_some() {
            let (bucket, _) = self.extract_bucket_from_uri(path)?;
            return self.get_or_create_operator(&bucket).await;
        }

        // Priority 3: No operator configured
        Err(Error::InvalidInput(
            "FileIO not configured with operator or credentials".to_string(),
        ))
    }

    /// Get or create an operator for the given bucket, using cache
    ///
    /// Uses double-checked locking pattern for thread-safe caching.
    /// All buckets are in the same region (default_region), so we only cache by bucket name.
    async fn get_or_create_operator(&self, bucket: &str) -> Result<Operator> {
        // Fast path: read lock
        {
            let cache = self
                .operator_cache
                .read()
                .map_err(|e| Error::IoError(format!("Failed to acquire read lock: {}", e)))?;
            if let Some(op) = cache.get(bucket) {
                return Ok(op.clone());
            }
        }

        // Slow path: write lock
        let mut cache = self
            .operator_cache
            .write()
            .map_err(|e| Error::IoError(format!("Failed to acquire write lock: {}", e)))?;

        // Double-check pattern
        if let Some(op) = cache.get(bucket) {
            return Ok(op.clone());
        }

        let op = self.create_s3_operator(bucket, &self.default_region)?;
        cache.insert(bucket.to_string(), op.clone());
        Ok(op)
    }

    /// Create an S3 operator for the given bucket and region
    fn create_s3_operator(&self, bucket: &str, region: &str) -> Result<Operator> {
        use opendal::services::S3;

        let credentials = self.credentials.as_ref().ok_or_else(|| {
            Error::InvalidInput("No credentials available for S3 operator creation".to_string())
        })?;

        let builder = S3::default()
            .bucket(bucket)
            .region(region)
            .access_key_id(&credentials.access_key_id)
            .secret_access_key(&credentials.secret_access_key);

        let builder = if let Some(ref token) = credentials.session_token {
            builder.session_token(token)
        } else {
            builder
        };

        Ok(Operator::new(builder)
            .map_err(|e| Error::IoError(format!("Failed to create S3 operator: {}", e)))?
            .finish())
    }

    /// Normalize path by stripping S3 URI prefix if present
    /// Converts "s3://bucket/path/to/file" to "path/to/file"
    fn normalize_path<'a>(&self, path: &'a str) -> &'a str {
        path.strip_prefix("s3://")
            .and_then(|stripped| stripped.find('/').map(|pos| &stripped[pos + 1..]))
            .unwrap_or(path)
    }

    /// Read a file completely
    pub async fn read(&self, path: &str) -> Result<Vec<u8>> {
        let operator = self.get_operator_for_path(path).await?;
        let normalized = self.normalize_path(path);
        operator
            .read(normalized)
            .await
            .map(|b| b.to_vec())
            .map_err(|e| Error::IoError(format!("Failed to read {}: {}", path, e)))
    }

    /// Write data to a file
    pub async fn write(&self, path: &str, data: Vec<u8>) -> Result<()> {
        let operator = self.get_operator_for_path(path).await?;
        let normalized = self.normalize_path(path);
        operator
            .write(normalized, data)
            .await
            .map(|_| ()) // Discard Metadata return value
            .map_err(|e| Error::IoError(format!("Failed to write {}: {}", path, e)))
    }

    /// Check if a file exists
    pub async fn exists(&self, path: &str) -> Result<bool> {
        let operator = self.get_operator_for_path(path).await?;
        let normalized = self.normalize_path(path);
        match operator.exists(normalized).await {
            Ok(exists) => Ok(exists),
            Err(e) => Err(Error::IoError(format!(
                "Failed to check existence of {}: {}",
                path, e
            ))),
        }
    }

    /// Delete a file
    pub async fn delete(&self, path: &str) -> Result<()> {
        let operator = self.get_operator_for_path(path).await?;
        let normalized = self.normalize_path(path);
        operator
            .delete(normalized)
            .await
            .map_err(|e| Error::IoError(format!("Failed to delete {}: {}", path, e)))
    }
}

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

    #[tokio::test]
    async fn test_file_io_creation() {
        let op = Operator::via_iter(opendal::Scheme::Memory, []).unwrap();
        let _file_io = FileIO::new(op);
        // Just verify it compiles and constructs
    }
}