// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements.  See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership.  The ASF licenses this file
// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License.  You may obtain a copy of the License at
//
//   http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied.  See the License for the
// specific language governing permissions and limitations
// under the License.

use super::backend::*;
use opendal_core::raw::*;
use opendal_core::*;

/// Reader returned by this backend.
pub struct RedisReader {
    backend: RedisBackend,
    path: String,
}

impl RedisReader {
    pub(super) fn new(backend: RedisBackend, path: &str, _: OpRead) -> Self {
        Self {
            backend,
            path: path.to_string(),
        }
    }
}

impl oio::StreamRead for RedisReader {
    async fn open(&self, range: BytesRange) -> Result<(RpRead, Box<dyn oio::ReadStreamDyn>)> {
        let backend = &self.backend;
        let path = self.path.as_str();
        let p = build_abs_path(&backend.root, path);

        let (buffer, metadata) = if range.is_full() {
            // Full read - use GET
            match backend.core.get(&p).await? {
                Some(bs) => {
                    let metadata =
                        Metadata::new(EntryMode::FILE).with_content_length(bs.len() as u64);
                    (bs, Some(metadata))
                }
                None => return Err(Error::new(ErrorKind::NotFound, "key not found in redis")),
            }
        } else {
            // Range read - use GETRANGE
            let content_length = match backend.core.len(&p).await? {
                Some(v) => v,
                None => return Err(Error::new(ErrorKind::NotFound, "key not found in redis")),
            };
            let content_range = range.to_content_range(content_length)?;

            let buffer = if content_range.is_empty() {
                Buffer::new()
            } else {
                let start: isize = content_range.start.try_into().map_err(|err| {
                    Error::new(ErrorKind::Unexpected, "range start exceeds isize::MAX")
                        .set_source(err)
                })?;
                let end: isize = (content_range.end - 1).try_into().map_err(|err| {
                    Error::new(ErrorKind::Unexpected, "range end exceeds isize::MAX")
                        .set_source(err)
                })?;
                match backend.core.get_range(&p, start, end).await? {
                    Some(bs) => bs,
                    None => {
                        return Err(Error::new(ErrorKind::NotFound, "key not found in redis"));
                    }
                }
            };
            let metadata =
                Metadata::new(EntryMode::FILE).with_content_length(content_length as u64);
            (buffer, Some(metadata))
        };

        let rp = metadata.map_or_else(RpRead::default, RpRead::new);
        Ok((rp, Box::new(buffer) as Box<dyn oio::ReadStreamDyn>))
    }
}
