//! Content-addressable managed storage service.
//!
//! Provides server-side file storage with:
//! - BLAKE3 content hashing for deduplication
//! - Hierarchical storage layout: `<root>/<hash[0:2]>/<hash[2:4]>/<full_hash>`
//! - Integrity verification on read (optional)

use std::path::{Path, PathBuf};

use tokio::{
  fs,
  io::{AsyncRead, AsyncReadExt, AsyncWriteExt, BufReader},
};
use tracing::{debug, info, warn};

use crate::{
  error::{PinakesError, Result},
  model::ContentHash,
};

/// Content-addressable storage service for managed files.
#[derive(Debug, Clone)]
pub struct ManagedStorageService {
  root_dir:        PathBuf,
  max_upload_size: u64,
  verify_on_read:  bool,
}

impl ManagedStorageService {
  /// Create a new managed storage service.
  #[must_use]
  pub const fn new(
    root_dir: PathBuf,
    max_upload_size: u64,
    verify_on_read: bool,
  ) -> Self {
    Self {
      root_dir,
      max_upload_size,
      verify_on_read,
    }
  }

  /// Initialize the storage directory structure.
  ///
  /// # Errors
  ///
  /// Returns [`PinakesError`] if the directory cannot be created.
  pub async fn init(&self) -> Result<()> {
    fs::create_dir_all(&self.root_dir).await?;
    info!(path = %self.root_dir.display(), "initialized managed storage");
    Ok(())
  }

  /// Get the storage path for a content hash.
  ///
  /// Layout: `<root>/<hash[0:2]>/<hash[2:4]>/<full_hash>`
  #[must_use]
  pub fn path(&self, hash: &ContentHash) -> PathBuf {
    let h = &hash.0;
    if h.len() >= 4 {
      self.root_dir.join(&h[0..2]).join(&h[2..4]).join(h)
    } else {
      // Fallback for short hashes (shouldn't happen with BLAKE3)
      self.root_dir.join(h)
    }
  }

  /// Check if a blob exists in storage.
  #[must_use]
  pub fn exists(&self, hash: &ContentHash) -> bool {
    self.path(hash).exists()
  }

  /// Store a file from an async reader, computing the hash as we go.
  ///
  /// Returns the content hash and file size.
  /// If the file already exists with the same hash, returns early
  /// (deduplication).
  ///
  /// # Errors
  ///
  /// Returns [`PinakesError`] if the file cannot be stored or exceeds the size
  /// limit.
  pub async fn store_stream<R: AsyncRead + Unpin>(
    &self,
    mut reader: R,
  ) -> Result<(ContentHash, u64)> {
    // First, stream to a temp file while computing the hash
    let temp_dir = self.root_dir.join("temp");
    fs::create_dir_all(&temp_dir).await?;

    let temp_id = uuid::Uuid::now_v7();
    let temp_path = temp_dir.join(temp_id.to_string());

    let mut hasher = blake3::Hasher::new();
    let mut temp_file = fs::File::create(&temp_path).await?;
    let mut total_size = 0u64;

    let mut buf = vec![0u8; 64 * 1024]; // 64KB buffer
    loop {
      let n = reader.read(&mut buf).await?;
      if n == 0 {
        break;
      }

      total_size += n as u64;
      if total_size > self.max_upload_size {
        // Clean up temp file
        drop(temp_file);
        let _ = fs::remove_file(&temp_path).await;
        return Err(PinakesError::UploadTooLarge(total_size));
      }

      hasher.update(&buf[..n]);
      temp_file.write_all(&buf[..n]).await?;
    }

    temp_file.flush().await?;
    temp_file.sync_all().await?;
    drop(temp_file);

    let hash = ContentHash::new(hasher.finalize().to_hex().to_string());
    let final_path = self.path(&hash);

    // Check if file already exists (deduplication)
    if final_path.exists() {
      // Verify size matches
      let existing_meta = fs::metadata(&final_path).await?;
      if existing_meta.len() == total_size {
        debug!(hash = %hash, "blob already exists, deduplicating");
        let _ = fs::remove_file(&temp_path).await;
        return Ok((hash, total_size));
      }
      warn!(
          hash = %hash,
          expected = total_size,
          actual = existing_meta.len(),
          "size mismatch for existing blob, replacing"
      );
    }

    // Move temp file to final location
    if let Some(parent) = final_path.parent() {
      fs::create_dir_all(parent).await?;
    }
    fs::rename(&temp_path, &final_path).await?;

    info!(hash = %hash, size = total_size, "stored new blob");
    Ok((hash, total_size))
  }

  /// Store a file from a path.
  ///
  /// # Errors
  ///
  /// Returns [`PinakesError`] if the file cannot be opened or stored.
  pub async fn store_file(&self, path: &Path) -> Result<(ContentHash, u64)> {
    let file = fs::File::open(path).await?;
    let reader = BufReader::new(file);
    self.store_stream(reader).await
  }

  /// Store bytes directly.
  ///
  /// # Errors
  ///
  /// Returns [`PinakesError`] if the data cannot be stored or exceeds the size
  /// limit.
  pub async fn store_bytes(&self, data: &[u8]) -> Result<(ContentHash, u64)> {
    use std::io::Cursor;
    let cursor = Cursor::new(data);
    self.store_stream(cursor).await
  }

  /// Open a blob for reading.
  ///
  /// # Errors
  ///
  /// Returns [`PinakesError`] if the blob does not exist or cannot be opened.
  pub async fn open(&self, hash: &ContentHash) -> Result<fs::File> {
    let path = self.path(hash);
    if !path.exists() {
      return Err(PinakesError::BlobNotFound(hash.0.clone()));
    }

    if self.verify_on_read {
      self.verify(hash).await?;
    }

    fs::File::open(&path).await.map_err(PinakesError::Io)
  }

  /// Read a blob entirely into memory.
  ///
  /// # Errors
  ///
  /// Returns [`PinakesError`] if the blob does not exist, cannot be read, or
  /// fails integrity check.
  pub async fn read(&self, hash: &ContentHash) -> Result<Vec<u8>> {
    let path = self.path(hash);
    if !path.exists() {
      return Err(PinakesError::BlobNotFound(hash.0.clone()));
    }

    let data = fs::read(&path).await?;

    if self.verify_on_read {
      let computed = blake3::hash(&data);
      if computed.to_hex().to_string() != hash.0 {
        return Err(PinakesError::StorageIntegrity(format!(
          "hash mismatch for blob {hash}"
        )));
      }
    }

    Ok(data)
  }

  /// Verify the integrity of a stored blob.
  ///
  /// # Errors
  ///
  /// Returns [`PinakesError`] if the blob cannot be read or has a hash
  /// mismatch.
  pub async fn verify(&self, hash: &ContentHash) -> Result<bool> {
    let path = self.path(hash);
    if !path.exists() {
      return Ok(false);
    }

    let file = fs::File::open(&path).await?;
    let mut reader = BufReader::new(file);
    let mut hasher = blake3::Hasher::new();
    let mut buf = vec![0u8; 64 * 1024];

    loop {
      let n = reader.read(&mut buf).await?;
      if n == 0 {
        break;
      }
      hasher.update(&buf[..n]);
    }

    let computed = hasher.finalize().to_hex().to_string();
    if computed != hash.0 {
      warn!(
          expected = %hash,
          computed = %computed,
          "blob integrity check failed"
      );
      return Err(PinakesError::StorageIntegrity(format!(
        "hash mismatch: expected {hash}, computed {computed}"
      )));
    }

    debug!(hash = %hash, "blob integrity verified");
    Ok(true)
  }

  /// Delete a blob from storage.
  ///
  /// # Errors
  ///
  /// Returns [`PinakesError`] if the blob cannot be removed.
  pub async fn delete(&self, hash: &ContentHash) -> Result<()> {
    let path = self.path(hash);
    if path.exists() {
      fs::remove_file(&path).await?;
      info!(hash = %hash, "deleted blob");

      // Try to remove empty parent directories
      if let Some(parent) = path.parent() {
        let _ = fs::remove_dir(parent).await;
        if let Some(grandparent) = parent.parent() {
          let _ = fs::remove_dir(grandparent).await;
        }
      }
    }
    Ok(())
  }

  /// Get the size of a stored blob.
  ///
  /// # Errors
  ///
  /// Returns [`PinakesError`] if the blob does not exist or metadata cannot be
  /// read.
  pub async fn size(&self, hash: &ContentHash) -> Result<u64> {
    let path = self.path(hash);
    if !path.exists() {
      return Err(PinakesError::BlobNotFound(hash.0.clone()));
    }
    let meta = fs::metadata(&path).await?;
    Ok(meta.len())
  }

  /// List all blob hashes in storage.
  ///
  /// # Errors
  ///
  /// Returns [`PinakesError`] if the storage directory cannot be read.
  pub async fn list_all(&self) -> Result<Vec<ContentHash>> {
    let mut hashes = Vec::new();

    let mut entries = fs::read_dir(&self.root_dir).await?;
    while let Some(entry) = entries.next_entry().await? {
      let path = entry.path();
      if path.is_dir() && path.file_name().map(std::ffi::OsStr::len) == Some(2)
      {
        let mut sub_entries = fs::read_dir(&path).await?;
        while let Some(sub_entry) = sub_entries.next_entry().await? {
          let sub_path = sub_entry.path();
          if sub_path.is_dir()
            && sub_path.file_name().map(std::ffi::OsStr::len) == Some(2)
          {
            let mut file_entries = fs::read_dir(&sub_path).await?;
            while let Some(file_entry) = file_entries.next_entry().await? {
              let file_path = file_entry.path();
              if file_path.is_file()
                && let Some(name) = file_path.file_name()
              {
                hashes
                  .push(ContentHash::new(name.to_string_lossy().to_string()));
              }
            }
          }
        }
      }
    }

    Ok(hashes)
  }

  /// Calculate total storage used by all blobs.
  ///
  /// # Errors
  ///
  /// Returns [`StorageError`] if listing blobs or querying sizes fails.
  pub async fn total_size(&self) -> Result<u64> {
    let hashes = self.list_all().await?;
    let mut total = 0u64;
    for hash in hashes {
      if let Ok(size) = self.size(&hash).await {
        total += size;
      }
    }
    Ok(total)
  }

  /// Clean up any orphaned temp files.
  ///
  /// # Errors
  ///
  /// Returns [`PinakesError`] if the temp directory cannot be read.
  pub async fn cleanup_temp(&self) -> Result<u64> {
    let temp_dir = self.root_dir.join("temp");
    if !temp_dir.exists() {
      return Ok(0);
    }

    let mut count = 0u64;
    let mut entries = fs::read_dir(&temp_dir).await?;
    while let Some(entry) = entries.next_entry().await? {
      let path = entry.path();
      if path.is_file() {
        // Check if temp file is old (> 1 hour)
        if let Ok(meta) = fs::metadata(&path).await
          && let Ok(modified) = meta.modified()
        {
          let age = std::time::SystemTime::now()
            .duration_since(modified)
            .unwrap_or_default();
          if age.as_secs() > 3600 {
            let _ = fs::remove_file(&path).await;
            count += 1;
          }
        }
      }
    }

    if count > 0 {
      info!(count, "cleaned up orphaned temp files");
    }
    Ok(count)
  }
}

#[cfg(test)]
mod tests {
  use tempfile::tempdir;

  use super::*;

  #[tokio::test]
  async fn test_store_and_retrieve() {
    let dir = tempdir().unwrap();
    let service =
      ManagedStorageService::new(dir.path().to_path_buf(), 1024 * 1024, false);
    service.init().await.unwrap();

    let data = b"hello, world!";
    let (hash, size) = service.store_bytes(data).await.unwrap();

    assert_eq!(size, data.len() as u64);
    assert!(service.exists(&hash));

    let retrieved = service.read(&hash).await.unwrap();
    assert_eq!(retrieved, data);
  }

  #[tokio::test]
  async fn test_deduplication() {
    let dir = tempdir().unwrap();
    let service =
      ManagedStorageService::new(dir.path().to_path_buf(), 1024 * 1024, false);
    service.init().await.unwrap();

    let data = b"duplicate content";
    let (hash1, _) = service.store_bytes(data).await.unwrap();
    let (hash2, _) = service.store_bytes(data).await.unwrap();

    assert_eq!(hash1.0, hash2.0);
    assert_eq!(service.list_all().await.unwrap().len(), 1);
  }

  #[tokio::test]
  async fn test_verify_integrity() {
    let dir = tempdir().unwrap();
    let service =
      ManagedStorageService::new(dir.path().to_path_buf(), 1024 * 1024, true);
    service.init().await.unwrap();

    let data = b"verify me";
    let (hash, _) = service.store_bytes(data).await.unwrap();

    assert!(service.verify(&hash).await.unwrap());
  }

  #[tokio::test]
  async fn test_upload_too_large() {
    let dir = tempdir().unwrap();
    let service =
      ManagedStorageService::new(dir.path().to_path_buf(), 100, false);
    service.init().await.unwrap();

    let data = vec![0u8; 200];
    let result = service.store_bytes(&data).await;

    assert!(matches!(result, Err(PinakesError::UploadTooLarge(_))));
  }

  #[tokio::test]
  async fn test_delete() {
    let dir = tempdir().unwrap();
    let service =
      ManagedStorageService::new(dir.path().to_path_buf(), 1024 * 1024, false);
    service.init().await.unwrap();

    let data = b"delete me";
    let (hash, _) = service.store_bytes(data).await.unwrap();
    assert!(service.exists(&hash));

    service.delete(&hash).await.unwrap();
    assert!(!service.exists(&hash));
  }
}