// 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.

#include "io/fs/http_file_reader.h"

#include <curl/curl.h>

#include <curl/easy.h>

#include <algorithm>

#include "common/logging.h"

namespace doris::io {

Result<FileReaderSPtr> HttpFileReader::create(const std::string& url,

                                              const std::map<std::string, std::string>& props,

                                              const FileReaderOptions& opts,

                                              RuntimeProfile* /*profile*/) {

    OpenFileInfo ofi;

    ofi.path = Path(url);

    ofi.extend_info = props;

    auto reader = std::make_shared<HttpFileReader>(ofi, url, opts.mtime);

    // Open the file to detect Range support and validate configuration

    RETURN_IF_ERROR_RESULT(reader->open(opts));

    return reader;

}

HttpFileReader::HttpFileReader(const OpenFileInfo& fileInfo, std::string url, int64_t mtime)

        : _extend_kv(fileInfo.extend_info),

          _path(fileInfo.path),

          _url(std::move(url)),

          _client(std::make_unique<HttpClient>()),

          _mtime(mtime) {

    auto etag_iter = _extend_kv.find("etag");

    if (etag_iter != _extend_kv.end()) {

        _etag = etag_iter->second;

    }

    auto lm_iter = _extend_kv.find("last_modified");

    if (lm_iter != _extend_kv.end()) {

        _last_modified = std::stoll(lm_iter->second);

    }

    auto size_iter = _extend_kv.find("file_size");

    if (size_iter != _extend_kv.end()) {

        _file_size = std::stoull(size_iter->second);

        _initialized = true;

    }

    // Parse configuration for non-Range request handling

    auto enable_range_iter = _extend_kv.find("http.enable.range.request");

    if (enable_range_iter != _extend_kv.end()) {

        // Convert to lowercase for case-insensitive comparison

        std::string value = enable_range_iter->second;

        std::transform(value.begin(), value.end(), value.begin(), ::tolower);

        _enable_range_request = (value != "false" && value != "0");

    }

    auto max_size_iter = _extend_kv.find("http.max.request.size.bytes");

    if (max_size_iter != _extend_kv.end()) {

        try {

            _max_request_size_bytes = std::stoull(max_size_iter->second);

        } catch (const std::exception& _) {

            LOG(WARNING) << "Invalid http.max.request.size.bytes value: " << max_size_iter->second

                         << ", using default: " << DEFAULT_MAX_REQUEST_SIZE;

            _max_request_size_bytes = DEFAULT_MAX_REQUEST_SIZE;

        }

    }

    _read_buffer = std::make_unique<char[]>(READ_BUFFER_SIZE);

}

HttpFileReader::~HttpFileReader() {

    static_cast<void>(close());

}

Status HttpFileReader::open(const FileReaderOptions& opts) {

    if (_initialized) {

        return Status::OK();

    }

    // Step 1: HEAD request to get file metadata

    RETURN_IF_ERROR(prepare_client(/*set_fail_on_error=*/true));

    _client->set_method(HttpMethod::HEAD);

    RETURN_IF_ERROR(_client->execute());

    uint64_t content_length = 0;

    RETURN_IF_ERROR(_client->get_content_length(&content_length));

    _file_size = content_length;

    _size_known = true;

    // Step 2: Check if Range request is disabled by configuration

    if (!_enable_range_request) {

        // User explicitly disabled Range requests, use non-Range mode directly

        _range_supported = false;

        LOG(INFO) << "Range requests disabled by configuration for " << _url

                  << ", using non-Range mode. File size: " << _file_size << " bytes";

        // Check if file size exceeds limit for non-Range mode

        if (_file_size > _max_request_size_bytes) {

            return Status::InternalError(

                    "Non-Range mode: file size ({} bytes) exceeds maximum allowed size ({} bytes, "

                    "configured by http.max.request.size.bytes). URL: {}",

                    _file_size, _max_request_size_bytes, _url);

        }

        LOG(INFO) << "Non-Range mode validated for " << _url << ", file size: " << _file_size

                  << " bytes, max allowed: " << _max_request_size_bytes << " bytes";

    } else {

        // Step 3: Range request is enabled (default), detect Range support

        VLOG(1) << "Detecting Range support for URL: " << _url;

        RETURN_IF_ERROR(detect_range_support());

        // Step 4: Validate Range support detection result

        if (!_range_supported) {

            // Server does not support Range and Range is required

            return Status::NotSupported(

                    "HTTP server does not support Range requests (RFC 7233), which is required "

                    "for reading files. File size: {} bytes, URL: {}. "

                    "To allow reading without Range support, set "

                    "'http.enable.range.request'='false' "

                    "in properties and configure 'http.max.request.size.bytes' appropriately "

                    "(note: this may cause high memory usage for large files).",

                    _file_size, _url);

        }

        LOG(INFO) << "HTTP server supports Range requests for " << _url;

    }

    _initialized = true;

    return Status::OK();

}

Status HttpFileReader::read_at_impl(size_t offset, Slice result, size_t* bytes_read,

                                    const IOContext* /*io_ctx*/) {

    VLOG(2) << "HttpFileReader::read_at_impl offset=" << offset << " size=" << result.size

            << " url=" << _url << " range_supported=" << _range_supported;

    if (!_read_buffer) {

        _read_buffer = std::make_unique<char[]>(READ_BUFFER_SIZE);

    }

    size_t to_read = result.size;

    size_t buffer_offset = 0;

    if (_size_known && offset >= _file_size) {

        *bytes_read = 0;

        return Status::OK();

    }

    // For non-Range mode, prioritize full file cache

    if (!_range_supported && _full_file_cached) {

        if (offset >= _full_file_cache.size()) {

            *bytes_read = 0;

            return Status::OK();

        }

        size_t available = _full_file_cache.size() - offset;

        size_t copy_len = std::min(available, to_read);

        std::memcpy(result.data, _full_file_cache.data() + offset, copy_len);

        *bytes_read = copy_len;

        VLOG(2) << "Full file cache hit: copied " << copy_len << " bytes from offset " << offset;

        return Status::OK();

    }

    // Try to serve from buffer cache

    if (offset >= _buffer_start && offset < _buffer_end) {

        size_t buffer_idx = offset - _buffer_start;

        size_t available = _buffer_end - offset;

        size_t copy_len = std::min(available, to_read);

        DCHECK(buffer_idx + copy_len <= READ_BUFFER_SIZE)

                << "Buffer overflow: buffer_idx=" << buffer_idx << " copy_len=" << copy_len

                << " READ_BUFFER_SIZE=" << READ_BUFFER_SIZE;

        std::memcpy(result.data, _read_buffer.get() + buffer_idx, copy_len);

        buffer_offset += copy_len;

        to_read -= copy_len;

        offset += copy_len;

        VLOG(2) << "Buffer cache hit: copied " << copy_len << " bytes";

    } else {

        // Buffer miss, invalidate cache

        _buffer_start = 0;

        _buffer_end = 0;

        VLOG(2) << "Buffer cache miss";

    }

    if (to_read == 0) {

        *bytes_read = buffer_offset;

        return Status::OK();

    }

    size_t remaining = to_read;

    if (_size_known) {

        uint64_t left = (_file_size > offset) ? (_file_size - offset) : 0;

        if (left == 0) {

            *bytes_read = buffer_offset;

            return Status::OK();

        }

        remaining = std::min<uint64_t>(to_read, left);

    }

    size_t req_len = (remaining > READ_BUFFER_SIZE) ? remaining : READ_BUFFER_SIZE;

    VLOG(2) << "Issuing HTTP GET request: offset=" << offset << " req_len=" << req_len

            << " with_range=" << _range_supported;

    // Prepare and initialize the HTTP client for GET request

    RETURN_IF_ERROR(prepare_client(/*set_fail_on_error=*/false));

    _client->set_method(HttpMethod::GET);

    _client->set_header("Expect", "");

    _client->set_header("Connection", "close");

    bool with_range = _range_supported;

    if (with_range) _client->set_range(offset, req_len);

    std::string buf;

    buf.reserve(req_len);

    size_t total_received = 0;

    bool size_limit_exceeded = false;

    auto cb = [&](const void* data, size_t len) {

        total_received += len;

        // If using non-Range mode, enforce size limit to prevent OOM

        if (!_range_supported && total_received > _max_request_size_bytes) {

            size_limit_exceeded = true;

            VLOG(1) << "Stopping download: received " << total_received << " bytes, exceeds limit "

                    << _max_request_size_bytes;

            return false; // Stop receiving - this will cause CURL to return an error

        }

        buf.append(reinterpret_cast<const char*>(data), len);

        return true;

    };

    Status exec_status = _client->execute(cb);

    // Check if we stopped due to size limit - this is expected behavior

    if (size_limit_exceeded) {

        return Status::InternalError(

                "HTTP response too large: received {} bytes, exceeds maximum allowed size {} "

                "bytes (configured by max.request.size.bytes). URL: {}",

                total_received, _max_request_size_bytes, _url);

    }

    // If there's an error and it's not due to our size limit check, return it

    RETURN_IF_ERROR(exec_status);

    long http_status = _client->get_http_status();

    VLOG(2) << "HTTP response: status=" << http_status << " received_bytes=" << buf.size();

    if (buf.empty()) {

        *bytes_read = buffer_offset;

        return Status::OK();

    }

    // Defensive check: if we sent Range but server returned 200 instead of 206

    // This should rarely happen since we detect Range support in open()

    if (with_range && offset > 0 && http_status == 200) {

        LOG(ERROR) << "HTTP server unexpectedly does not support Range requests for " << _url

                   << " (this should have been detected in open()). HTTP status: " << http_status

                   << ", received: " << buf.size()

                   << " bytes. This indicates a server behavior change.";

        return Status::InternalError(

                "HTTP server does not support Range requests but this was not detected during "

                "file open. This may indicate the server behavior has changed. "

                "HTTP status: {}, received: {} bytes. URL: {}",

                http_status, buf.size(), _url);

    }

    // Handle non-Range mode: cache the full file on first download

    if (!_range_supported && !_full_file_cached) {

        // Cache the complete file content for subsequent reads

        _full_file_cache = std::move(buf);

        _full_file_cached = true;

        VLOG(2) << "Cached full file: " << _full_file_cache.size() << " bytes";

        // Serve the requested portion from cache

        if (offset >= _full_file_cache.size()) {

            *bytes_read = buffer_offset;

            return Status::OK();

        }

        size_t available = _full_file_cache.size() - offset;

        size_t copy_len = std::min(available, remaining);

        std::memcpy(result.data + buffer_offset, _full_file_cache.data() + offset, copy_len);

        *bytes_read = buffer_offset + copy_len;

        return Status::OK();

    }

    if (to_read > READ_BUFFER_SIZE) {

        if (buf.size() > remaining) {

            return Status::InternalError("HTTP response larger than requested buffer");

        }

        std::memcpy(result.data + buffer_offset, buf.data(), buf.size());

        buffer_offset += buf.size();

    } else {

        size_t cached = std::min(buf.size(), (size_t)READ_BUFFER_SIZE);

        std::memcpy(_read_buffer.get(), buf.data(), cached);

        _buffer_start = offset;

        _buffer_end = offset + cached;

        size_t copy_len = std::min(remaining, cached);

        std::memcpy(result.data + buffer_offset, _read_buffer.get(), copy_len);

        buffer_offset += copy_len;

    }

    if (!_size_known && with_range && buf.size() < req_len) {

        _size_known = true;

        _file_size = offset + buf.size();

    }

    *bytes_read = buffer_offset;

    return Status::OK();

}

Status HttpFileReader::close() {

    if (_closed.exchange(true)) {

        return Status::OK();

    }

    // Release buffer memory (1MB)

    _read_buffer.reset();

    _buffer_start = 0;

    _buffer_end = 0;

    // Release full file cache

    _full_file_cache.clear();

    _full_file_cache.shrink_to_fit();

    _full_file_cached = false;

    // Release HttpClient resources

    _client.reset();

    return Status::OK();

}

Status HttpFileReader::prepare_client(bool set_fail_on_error) {

    if (!_client) {

        return Status::InternalError("HttpClient is not initialized");

    }

    // Initialize the HTTP client with URL

    RETURN_IF_ERROR(_client->init(_url, set_fail_on_error));

    // Set custom headers from extend_kv

    for (const auto& kv : _extend_kv) {

        if (kv.first.rfind("http.header.", 0) == 0) {

            _client->set_header(kv.first.substr(strlen("http.header.")), kv.second);

        }

    }

    return Status::OK();

}

Status HttpFileReader::detect_range_support() {

    // Send a small Range request to test if the server supports it

    // We request only the first byte to minimize data transfer

    RETURN_IF_ERROR(prepare_client(/*set_fail_on_error=*/false));

    _client->set_method(HttpMethod::GET);

    _client->set_range(0, 1); // Request only the first byte

    std::string test_buf;

    size_t received = 0;

    constexpr size_t MAX_TEST_SIZE = 10240; // 10KB max for test

    bool stopped_by_limit = false;

    auto cb = [&](const void* data, size_t len) {

        received += len;

        // Limit test data to prevent downloading too much

        if (received > MAX_TEST_SIZE) {

            stopped_by_limit = true;

            VLOG(2) << "Stopping Range detection test after receiving " << received << " bytes";

            return false; // This will cause CURL to stop with an error

        }

        test_buf.append(reinterpret_cast<const char*>(data), len);

        return true;

    };

    Status exec_status = _client->execute(cb);

    // If we stopped because of size limit, it's not a real error

    if (!exec_status.ok() && stopped_by_limit) {

        VLOG(1) << "Range detection stopped at size limit (expected): " << exec_status.to_string();

        // Continue processing - this is expected behavior

    } else if (!exec_status.ok()) {

        // Real error

        return exec_status;

    }

    long http_status = _client->get_http_status();

    if (http_status == 206) {

        // HTTP 206 Partial Content - server supports Range requests

        _range_supported = true;

        VLOG(1) << "Range support detected (HTTP 206) for " << _url << ", received "

                << test_buf.size() << " bytes";

    } else if (http_status == 200) {

        // HTTP 200 OK - server does not support Range requests

        // It returned the full file (or a large portion)

        _range_supported = false;

        VLOG(1) << "Range not supported (HTTP 200) for " << _url << ", received " << test_buf.size()

                << " bytes in test";

        // If we received a lot of data, it's likely the full file

        if (test_buf.size() >= MAX_TEST_SIZE || stopped_by_limit) {

            LOG(WARNING) << "Server returned " << received << "+ bytes for Range test, "

                         << "indicating no Range support for " << _url;

        }

    } else {

        // Unexpected status code

        LOG(WARNING) << "Unexpected HTTP status " << http_status << " during Range detection for "

                     << _url << ", assuming Range is not supported";

        _range_supported = false;

    }

    return Status::OK();

}

} // namespace doris::io