// See the file "COPYING" in the main distribution directory for copyright.

#pragma once

namespace zeek::detail {

class Pipe {
public:
    /**
     * Create a pair of file descriptors via pipe(), or aborts if it cannot.
     * @param flags0 file descriptor flags to set on read end of pipe.
     * @param flags1 file descriptor flags to set on write end of pipe.
     * @param status_flags0 descriptor status flags to set on read end of pipe.
     * @param status_flags1 descriptor status flags to set on write end of pipe.
     * @param fds may be supplied to open an existing file descriptors rather
     * than create ones from a new pipe.  Should point to memory containing
     * two consecutive file descriptors, the "read" one and then the "write" one.
     */
    explicit Pipe(int flags0 = 0, int flags1 = 0, int status_flags0 = 0, int status_flags1 = 0, int* fds = nullptr);

    /**
     * Close the pair of file descriptors owned by the object.
     */
    ~Pipe();

    /**
     * Make a copy of another Pipe object (file descriptors are dup'd).
     */
    Pipe(const Pipe& other);

    /**
     * Assign a Pipe object by closing file descriptors and duping those of
     * the other.
     */
    Pipe& operator=(const Pipe& other);

    /**
     * @return the file descriptor associated with the read-end of the pipe.
     */
    int ReadFD() const { return fds[0]; }

    /**
     * @return the file descriptor associated with the write-end of the pipe.
     */
    int WriteFD() const { return fds[1]; }

    /**
     * Sets the given file descriptor flags for both the read and write end
     * of the pipe.
     */
    void SetFlags(int flags);

    /**
     * Unsets the given file descriptor flags for both the read and write end
     * of the pipe.
     */
    void UnsetFlags(int flags);

private:
    int fds[2];
    int flags[2];
    int status_flags[2];
};

/**
 * A pair of pipes that can be used for bi-directional IPC.
 */
class PipePair {
public:
    /**
     * Create a pair of pipes
     * @param flags  file descriptor flags to set on pipes
     * @status_flags  descriptor status flags to set on pipes
     * @fds  may be supplied to open existing file descriptors rather
     * than create ones from a new pair of pipes.  Should point to memory
     * containing four consecutive file descriptors, "read" end and "write" end
     * of the first pipe followed by the "read" end and "write" end of the
     * second pipe.
     */
    PipePair(int flags, int status_flags, int* fds = nullptr);

    /**
     * @return the pipe used for receiving input
     */
    Pipe& In() { return pipes[swapped]; }

    /**
     * @return the pipe used for sending output
     */
    Pipe& Out() { return pipes[! swapped]; }

    /**
     * @return the pipe used for receiving input
     */
    const Pipe& In() const { return pipes[swapped]; }

    /**
     * @return the pipe used for sending output
     */
    const Pipe& Out() const { return pipes[! swapped]; }

    /**
     * @return a file descriptor that may used for receiving messages by
     * polling/reading it.
     */
    int InFD() const { return In().ReadFD(); }

    /**
     * @return a file descriptor that may be used for sending messages by
     * writing to it.
     */
    int OutFD() const { return Out().WriteFD(); }

    /**
     * Swaps the meaning of the pipes in the pair.  E.g. call this after
     * fork()'ing so that the child process uses the right pipe for
     * reading/writing.
     */
    void Swap() { swapped = ! swapped; }

private:
    Pipe pipes[2];
    bool swapped = false;
};

} // namespace zeek::detail