/*

* DataSource

* (C) 1999-2007 Jack Lloyd

*     2012 Markus Wanner

*

* Botan is released under the Simplified BSD License (see license.txt)

*/

#ifndef BOTAN_DATA_SRC_H_

#define BOTAN_DATA_SRC_H_

#include <botan/secmem.h>

#include <iosfwd>

#include <memory>

#include <optional>

#include <span>

#include <string>

#include <string_view>

namespace Botan {

/**

* This class represents an abstract data source object.

*/

class BOTAN_PUBLIC_API(2, 0) DataSource {

   public:

      /**

      * Read from the source. Moves the internal offset so that every

      * call to read will return a new portion of the source.

      *

      * @param out the byte array to write the result to

      * @param length the length of the byte array out

      * @return length in bytes that was actually read and put

      * into out

      */

      [[nodiscard]] virtual size_t read(uint8_t out[], size_t length) = 0;

      virtual bool check_available(size_t n) = 0;

      /**

      * Read from the source but do not modify the internal

      * offset. Consecutive calls to peek() will return portions of

      * the source starting at the same position.

      *

      * @param out the byte array to write the output to

      * @param length the length of the byte array out

      * @param peek_offset the offset into the stream to read at

      * @return length in bytes that was actually read and put

      * into out

      */

      [[nodiscard]] virtual size_t peek(uint8_t out[], size_t length, size_t peek_offset) const = 0;

      /**

      * Test whether the source still has data that can be read.

      * @return true if there is no more data to read, false otherwise

      */

      virtual bool end_of_data() const = 0;

      /**

      * return the id of this data source

      * @return std::string representing the id of this data source

      */

      virtual std::string id() const { return ""; }

      /**

      * Read one byte.

      * @param out the byte to read to

      * @return length in bytes that was actually read and put

      * into out

      */

      size_t read_byte(uint8_t& out);

      /**

      * Read one byte.

      *

      * Returns nullopt if no further bytes are available

      */

      std::optional<uint8_t> read_byte();

      /**

      * Peek at one byte.

      * @param out an output byte

      * @return length in bytes that was actually read and put

      * into out

      */

      size_t peek_byte(uint8_t& out) const;

      /**

      * Discard the next N bytes of the data

      * @param N the number of bytes to discard

      * @return number of bytes actually discarded

      */

      size_t discard_next(size_t N);

      /**

      * @return number of bytes read so far.

      */

      virtual size_t get_bytes_read() const = 0;

      DataSource() = default;

      virtual ~DataSource() = default;

      DataSource(const DataSource&) = delete;

      DataSource(DataSource&&) = default;

      DataSource& operator=(const DataSource&) = delete;

      DataSource& operator=(DataSource&&) = default;

};

/**

* This class represents a Memory-Based DataSource

*/

class BOTAN_PUBLIC_API(2, 0) DataSource_Memory final : public DataSource {

   public:

      size_t read(uint8_t buf[], size_t length) override;

      size_t peek(uint8_t buf[], size_t length, size_t offset) const override;

      bool check_available(size_t n) override;

      bool end_of_data() const override;

      /**

      * Construct a memory source that reads from a string

      * @param in the string to read from

      */

      explicit DataSource_Memory(std::string_view in);

      /**

      * Construct a memory source that reads from a byte array

      * @param in the byte array to read from

      * @param length the length of the byte array

      */

      DataSource_Memory(const uint8_t in[], size_t length) : m_source(in, in + length), m_offset(0) {}

      /**

      * Construct a memory source that reads from a secure_vector

      * @param in the MemoryRegion to read from

      */

      explicit DataSource_Memory(secure_vector<uint8_t> in) : m_source(std::move(in)), m_offset(0) {}

      /**

      * Construct a memory source that reads from an arbitrary byte buffer

      * @param in the MemoryRegion to read from

      */

      explicit DataSource_Memory(std::span<const uint8_t> in) : m_source(in.begin(), in.end()), m_offset(0) {}

      /**

      * Construct a memory source that reads from a std::vector

      * @param in the MemoryRegion to read from

      */

      explicit DataSource_Memory(const std::vector<uint8_t>& in) : m_source(in.begin(), in.end()), m_offset(0) {}

      size_t get_bytes_read() const override { return m_offset; }

   private:

      secure_vector<uint8_t> m_source;

      size_t m_offset;

};

/**

* This class represents a Stream-Based DataSource.

*/

class BOTAN_PUBLIC_API(2, 0) DataSource_Stream final : public DataSource {

   public:

      size_t read(uint8_t buf[], size_t length) override;

      size_t peek(uint8_t buf[], size_t length, size_t offset) const override;

      bool check_available(size_t n) override;

      bool end_of_data() const override;

      std::string id() const override;

      BOTAN_FUTURE_EXPLICIT DataSource_Stream(std::istream& in, std::string_view id = "<std::istream>");

#if defined(BOTAN_TARGET_OS_HAS_FILESYSTEM)

      /**

      * Construct a Stream-Based DataSource from filesystem path

      * @param filename the path to the file

      * @param use_binary whether to treat the file as binary or not

      */

      BOTAN_FUTURE_EXPLICIT DataSource_Stream(std::string_view filename, bool use_binary = false);

#endif

      DataSource_Stream(const DataSource_Stream&) = delete;

      DataSource_Stream(DataSource_Stream&&) = delete;

      DataSource_Stream& operator=(const DataSource_Stream&) = delete;

      DataSource_Stream& operator=(DataSource_Stream&&) = delete;

      ~DataSource_Stream() override;

      size_t get_bytes_read() const override { return m_total_read; }

   private:

      const std::string m_identifier;

      std::unique_ptr<std::istream> m_source_memory;

      std::istream& m_source;

      size_t m_total_read;

};

}  // namespace Botan

#endif