use std::path::Path;
use std::pin::Pin;
use std::future::Future;
use std::io::{SeekFrom};
use std::sync::Arc;
use std::time::Duration;

use tokio::sync::Mutex;
use reqwest::Client;
use rusty_s3::{Bucket, Credentials, S3Action, actions, UrlStyle};
use url::Url;

use super::{VfsError, VfsStat, VfsDirEntry, open_flags::OpenFlags};

pub struct AsyncS3Vfs {
    bucket: Bucket,
    credentials: Credentials,
    client: Client,
}

struct AsyncS3FileState {
    key: String,
    mode: FileMode,
    position: u64,
    size: u64,
    data: Vec<u8>,
    write_buffer: Vec<u8>,
    mtime: std::time::SystemTime,
}

enum FileMode {
    Read,
    Write,
}

pub struct AsyncS3File {
    inner: Arc<Mutex<AsyncS3FileState>>,
    vfs: AsyncS3Vfs,
}

impl AsyncS3Vfs {
    pub fn new(
        endpoint: &str,
        region: &str,
        bucket_name: &str,
        access_key: &str,
        secret_key: &str,
    ) -> Result<Self, VfsError> {
        let endpoint_url = Url::parse(endpoint.trim_end_matches('/'))
            .map_err(|e| VfsError::Io(format!("Invalid S3 endpoint URL: {}", e)))?;

        let bucket = Bucket::new(
            endpoint_url,
            UrlStyle::Path,
            bucket_name.to_string(),
            region.to_string(),
        ).map_err(|e| VfsError::Io(format!("Failed to create S3 bucket config: {}", e)))?;

        let credentials = Credentials::new(access_key, secret_key);
        let client = Client::new();

        Ok(Self { bucket, credentials, client })
    }

    fn path_to_key(path: &Path) -> String {
        let s = path.to_string_lossy();
        s.strip_prefix('/').unwrap_or(&s).to_string()
    }

    async fn head_object(&self, key: &str) -> Result<(u64, std::time::SystemTime, String), VfsError> {
        let action = actions::HeadObject::new(&self.bucket, Some(&self.credentials), key);
        let url = action.sign(Duration::from_secs(3600));

        let resp = self.client
            .head(url.as_str())
            .send()
            .await
            .map_err(|e| VfsError::Io(format!("S3 HEAD failed: {}", e)))?;

        let status = resp.status();
        if status == 404 {
            return Err(VfsError::NotFound(key.to_string()));
        }
        if !status.is_success() {
            return Err(VfsError::Io(format!("HeadObject returned {}", status)));
        }

        let content_len: u64 = resp
            .headers()
            .get("Content-Length")
            .and_then(|v| v.to_str().ok())
            .and_then(|v| v.parse().ok())
            .unwrap_or(0);

        let last_modified = parse_last_modified(
            resp.headers()
                .get("Last-Modified")
                .and_then(|v| v.to_str().ok())
        );

        let etag = resp
            .headers()
            .get("ETag")
            .and_then(|v| v.to_str().ok())
            .map(|s| s.replace('"', ""))
            .unwrap_or_default();

        Ok((content_len, last_modified, etag))
    }

    async fn get_object(&self, key: &str) -> Result<Vec<u8>, VfsError> {
        let action = actions::GetObject::new(&self.bucket, Some(&self.credentials), key);
        let url = action.sign(Duration::from_secs(3600));

        let resp = self.client
            .get(url.as_str())
            .send()
            .await
            .map_err(|e| VfsError::Io(format!("S3 GET failed: {}", e)))?;

        let status = resp.status();
        if status == 404 {
            return Err(VfsError::NotFound(key.to_string()));
        }
        if !status.is_success() {
            return Err(VfsError::Io(format!("GetObject returned {}", status)));
        }

        let bytes = resp.bytes().await
            .map_err(|e| VfsError::Io(format!("Failed to read response body: {}", e)))?;

        Ok(bytes.to_vec())
    }

    async fn put_object(&self, key: &str, data: &[u8]) -> Result<String, VfsError> {
        let action = actions::PutObject::new(&self.bucket, Some(&self.credentials), key);
        let url = action.sign(Duration::from_secs(3600));

        let resp = self.client
            .put(url.as_str())
            .body(data.to_vec())
            .send()
            .await
            .map_err(|e| VfsError::Io(format!("S3 PUT failed: {}", e)))?;

        if !resp.status().is_success() {
            return Err(VfsError::Io(format!("PutObject returned {}", resp.status())));
        }

        let etag = resp
            .headers()
            .get("ETag")
            .and_then(|v| v.to_str().ok())
            .map(|s| s.replace('"', ""))
            .unwrap_or_default();

        Ok(etag)
    }

    async fn delete_object(&self, key: &str) -> Result<(), VfsError> {
        let action = actions::DeleteObject::new(&self.bucket, Some(&self.credentials), key);
        let url = action.sign(Duration::from_secs(3600));

        let resp = self.client
            .delete(url.as_str())
            .send()
            .await
            .map_err(|e| VfsError::Io(format!("S3 DELETE failed: {}", e)))?;

        if !resp.status().is_success() {
            return Err(VfsError::Io(format!("DeleteObject returned {}", resp.status())));
        }

        Ok(())
    }

    async fn list_objects(&self, prefix: &str) -> Result<Vec<VfsDirEntry>, VfsError> {
        let mut action = actions::ListObjectsV2::new(&self.bucket, Some(&self.credentials));
        if !prefix.is_empty() {
            action.with_prefix(prefix);
        }
        action.with_delimiter("/");

        let url = action.sign(Duration::from_secs(3600));

        let resp = self.client
            .get(url.as_str())
            .send()
            .await
            .map_err(|e| VfsError::Io(format!("S3 LIST failed: {}", e)))?;

        if !resp.status().is_success() {
            return Err(VfsError::Io(format!("ListObjectsV2 returned {}", resp.status())));
        }

        let body = resp.text().await
            .map_err(|e| VfsError::Io(format!("Failed to read LIST response: {}", e)))?;

        // Use rusty-s3's built-in parser
        let list_response = actions::ListObjectsV2::parse_response(&body)
            .map_err(|e| VfsError::Io(format!("Failed to parse LIST response: {}", e)))?;

        // Convert to VfsDirEntry
        let mut entries = Vec::new();
        for obj in list_response.contents {
            let name = obj.key.strip_prefix(prefix).unwrap_or(&obj.key).to_string();
            entries.push(VfsDirEntry {
                name,
                long_name: obj.key.clone(),
                stat: VfsStat {
                    size: obj.size,
                    mode: 0o644,
                    uid: 0,
                    gid: 0,
                    atime: std::time::SystemTime::UNIX_EPOCH,
                    mtime: std::time::SystemTime::UNIX_EPOCH,
                    is_dir: false,
                    is_symlink: false,
                },
            });
        }
        for prefix_elem in list_response.common_prefixes {
            let name = prefix_elem.prefix.strip_prefix(prefix).unwrap_or(&prefix_elem.prefix).trim_end_matches('/').to_string();
            entries.push(VfsDirEntry {
                name,
                long_name: prefix_elem.prefix.clone(),
                stat: VfsStat {
                    size: 0,
                    mode: 0o755,
                    uid: 0,
                    gid: 0,
                    atime: std::time::SystemTime::UNIX_EPOCH,
                    mtime: std::time::SystemTime::UNIX_EPOCH,
                    is_dir: true,
                    is_symlink: false,
                },
            });
        }

        Ok(entries)
    }
}

impl Clone for AsyncS3Vfs {
    fn clone(&self) -> Self {
        Self {
            bucket: self.bucket.clone(),
            credentials: self.credentials.clone(),
            client: self.client.clone(),
        }
    }
}

impl AsyncS3File {
    pub async fn new_read(vfs: AsyncS3Vfs, key: String) -> Result<Self, VfsError> {
        let (size, mtime, _) = vfs.head_object(&key).await?;

        Ok(Self {
            inner: Arc::new(Mutex::new(AsyncS3FileState {
                key,
                mode: FileMode::Read,
                position: 0,
                size,
                data: Vec::new(),
                write_buffer: Vec::new(),
                mtime,
            })),
            vfs,
        })
    }

    pub fn new_write(vfs: AsyncS3Vfs, key: String) -> Self {
        Self {
            inner: Arc::new(Mutex::new(AsyncS3FileState {
                key,
                mode: FileMode::Write,
                position: 0,
                size: 0,
                data: Vec::new(),
                write_buffer: Vec::new(),
                mtime: std::time::SystemTime::now(),
            })),
            vfs,
        }
    }
}

impl super::AsyncVfsFile for AsyncS3File {
    fn read<'a>(&'a mut self, buf: &'a mut [u8]) -> Pin<Box<dyn Future<Output = Result<usize, VfsError>> + Send + 'a>> {
        let inner = self.inner.clone();
        let vfs = self.vfs.clone();
        Box::pin(async move {
            let mut state = inner.lock().await;

            if state.position >= state.size {
                return Ok(0);
            }

            if state.data.is_empty() {
                let key = state.key.clone();
                state.data = vfs.get_object(&key).await?;
            }

            let remaining = state.size - state.position;
            let to_read = buf.len().min(remaining as usize);
            let start = state.position as usize;
            let end = start + to_read;

            buf[..to_read].copy_from_slice(&state.data[start..end]);
            state.position += to_read as u64;

            Ok(to_read)
        })
    }

    fn write<'a>(&'a mut self, buf: &'a [u8]) -> Pin<Box<dyn Future<Output = Result<usize, VfsError>> + Send + 'a>> {
        let inner = self.inner.clone();
        Box::pin(async move {
            let mut state = inner.lock().await;
            state.write_buffer.extend_from_slice(buf);
            Ok(buf.len())
        })
    }

    fn seek<'a>(&'a mut self, pos: SeekFrom) -> Pin<Box<dyn Future<Output = Result<u64, VfsError>> + Send + 'a>> {
        let inner = self.inner.clone();
        Box::pin(async move {
            let mut state = inner.lock().await;
            let new_pos = match pos {
                SeekFrom::Start(offset) => offset,
                SeekFrom::Current(offset) => {
                    ((state.position as i64) + offset).max(0) as u64
                }
                SeekFrom::End(offset) => {
                    ((state.size as i64) + offset).max(0) as u64
                }
            };
            state.position = new_pos.min(state.size);
            Ok(state.position)
        })
    }

    fn flush<'a>(&'a mut self) -> Pin<Box<dyn Future<Output = Result<(), VfsError>> + Send + 'a>> {
        let inner = self.inner.clone();
        let vfs = self.vfs.clone();
        Box::pin(async move {
            let mut state = inner.lock().await;
            if !state.write_buffer.is_empty() {
                let key = state.key.clone();
                let data = state.write_buffer.clone();
                vfs.put_object(&key, &data).await?;
                state.write_buffer.clear();
            }
            Ok(())
        })
    }
}

impl super::AsyncVfsBackend for AsyncS3Vfs {
    fn clone_boxed(&self) -> Box<dyn super::AsyncVfsBackend> {
        Box::new(self.clone())
    }

    fn read_dir<'a>(&'a self, path: &'a Path) -> Pin<Box<dyn Future<Output = Result<Vec<VfsDirEntry>, VfsError>> + Send + 'a>> {
        let prefix = Self::path_to_key(path);
        Box::pin(async move {
            self.list_objects(&prefix).await
        })
    }

    fn open_file<'a>(&'a self, path: &'a Path, flags: &'a OpenFlags) -> Pin<Box<dyn Future<Output = Result<Box<dyn super::AsyncVfsFile>, VfsError>> + Send + 'a>> {
        let key = Self::path_to_key(path);
        let vfs = self.clone();
        let is_write = flags.write;
        Box::pin(async move {
            if is_write {
                Ok(Box::new(AsyncS3File::new_write(vfs, key)) as Box<dyn super::AsyncVfsFile>)
            } else {
                let file = AsyncS3File::new_read(vfs, key).await?;
                Ok(Box::new(file) as Box<dyn super::AsyncVfsFile>)
            }
        })
    }

    fn stat<'a>(&'a self, path: &'a Path) -> Pin<Box<dyn Future<Output = Result<VfsStat, VfsError>> + Send + 'a>> {
        let key = Self::path_to_key(path);
        Box::pin(async move {
            let (size, mtime, _) = self.head_object(&key).await?;
            Ok(VfsStat {
                size,
                mode: 0o644,
                uid: 0,
                gid: 0,
                atime: mtime,
                mtime,
                is_dir: false,
                is_symlink: false,
            })
        })
    }

    fn create_dir<'a>(&'a self, path: &'a Path, _mode: u32) -> Pin<Box<dyn Future<Output = Result<(), VfsError>> + Send + 'a>> {
        let key = Self::path_to_key(path);
        if !key.ends_with('/') {
            let _key = format!("{}/", key);
        }
        Box::pin(async move {
            self.put_object(&key, &[]).await?;
            Ok(())
        })
    }

    fn remove_dir<'a>(&'a self, path: &'a Path) -> Pin<Box<dyn Future<Output = Result<(), VfsError>> + Send + 'a>> {
        let key = Self::path_to_key(path);
        let key = if key.ends_with('/') { key } else { format!("{}/", key) };
        Box::pin(async move {
            self.delete_object(&key).await?;
            Ok(())
        })
    }

    fn remove_file<'a>(&'a self, path: &'a Path) -> Pin<Box<dyn Future<Output = Result<(), VfsError>> + Send + 'a>> {
        let key = Self::path_to_key(path);
        Box::pin(async move {
            self.delete_object(&key).await?;
            Ok(())
        })
    }

    fn rename<'a>(&'a self, from: &'a Path, to: &'a Path) -> Pin<Box<dyn Future<Output = Result<(), VfsError>> + Send + 'a>> {
        let from_key = Self::path_to_key(from);
        let to_key = Self::path_to_key(to);
        Box::pin(async move {
            let data = self.get_object(&from_key).await?;
            self.put_object(&to_key, &data).await?;
            self.delete_object(&from_key).await?;
            Ok(())
        })
    }

    fn exists<'a>(&'a self, path: &'a Path) -> Pin<Box<dyn Future<Output = bool> + Send + 'a>> {
        let key = Self::path_to_key(path);
        Box::pin(async move {
            self.head_object(&key).await.is_ok()
        })
    }
}

fn parse_last_modified(header: Option<&str>) -> std::time::SystemTime {
    header
        .and_then(|s| chrono::DateTime::parse_from_rfc2822(s).ok())
        .map(|dt| std::time::SystemTime::UNIX_EPOCH + std::time::Duration::from_secs(dt.timestamp() as u64))
        .unwrap_or(std::time::SystemTime::now())
}