#ifndef _EMPACK_H_
#define _EMPACK_H_

#include <stdint.h>

/** Forward definitions of all types */
typedef enum empack_type_enum            empack_type_e;
typedef struct empack_map_pair_struct    empack_map_pair_t;
typedef struct empack_map_struct         empack_map_t;
typedef struct empack_array_struct       empack_array_t;
typedef struct empack_str_struct         empack_str_t;
typedef struct empack_bin_struct         empack_bin_t;
typedef struct empack_ext_struct         empack_ext_t;
typedef struct empack_obj_struct         empack_obj_t;
typedef enum empack_status_enum          empack_status_e;
typedef struct empack_struct             empack_t;

/**
 * Enum of the first bytes for each msgpack type. For types with a range of
 * values that could be the first byte, the lowest is used
 */
enum empack_type_enum {
    /** Positive FIXINT, stored in `empack_obj_t::val.uint8` */
    EMPACK_TYPE_POS_FIXINT = 0x00,
    /** FIXMAP, enum field `val.map` */
    EMPACK_TYPE_FIXMAP     = 0x80,
    /** FIXARRAY, enum field `val.map` */
    EMPACK_TYPE_FIXARRAY   = 0x90,
    EMPACK_TYPE_FIXSTR     = 0xa0,
    EMPACK_TYPE_NIL        = 0xc0,
    /**
     * Special error type reserved for a type parsing error. This type is never
     * used in the Msgpack spec.
     */
    EMPACK_TYPE_ERROR      = 0xc1,
    EMPACK_TYPE_FALSE      = 0xc2,
    EMPACK_TYPE_TRUE       = 0xc3,
    EMPACK_TYPE_BIN8       = 0xc4,
    EMPACK_TYPE_BIN16      = 0xc5,
    EMPACK_TYPE_BIN32      = 0xc6,
    EMPACK_TYPE_EXT8       = 0xc7,
    EMPACK_TYPE_EXT16      = 0xc8,
    EMPACK_TYPE_EXT32      = 0xc9,
    EMPACK_TYPE_FLOAT32    = 0xca,
    EMPACK_TYPE_FLOAT64    = 0xcb,
    EMPACK_TYPE_UINT8      = 0xcc,
    EMPACK_TYPE_UINT16     = 0xcd,
    EMPACK_TYPE_UINT32     = 0xce,
    EMPACK_TYPE_UINT64     = 0xcf,
    EMPACK_TYPE_INT8       = 0xd0,
    EMPACK_TYPE_INT16      = 0xd1,
    EMPACK_TYPE_INT32      = 0xd2,
    EMPACK_TYPE_INT64      = 0xd3,
    EMPACK_TYPE_FIXEXT1    = 0xd4,
    EMPACK_TYPE_FIXEXT2    = 0xd5,
    EMPACK_TYPE_FIXEXT4    = 0xd6,
    EMPACK_TYPE_FIXEXT8    = 0xd7,
    EMPACK_TYPE_FIXEXT16   = 0xd8,
    EMPACK_TYPE_STR8       = 0xd9,
    EMPACK_TYPE_STR16      = 0xda,
    EMPACK_TYPE_STR32      = 0xdb,
    EMPACK_TYPE_ARRAY16    = 0xdc,
    EMPACK_TYPE_ARRAY32    = 0xdd,
    EMPACK_TYPE_MAP16      = 0xde,
    EMPACK_TYPE_MAP32      = 0xdf,
    EMPACK_TYPE_NEG_FIXINT = 0xe0,
};

struct empack_map_struct {
    /** List of key-value pairs in the map */
    empack_map_pair_t *pairs;
    /** Number of key-value pairs expected to be in the map */
    uint32_t pair_count;
    /** Number of key-value pairs actually in the map */
    uint32_t pair_count_real;
};

struct empack_array_struct {
    /** List of the objects in the array */
    empack_obj_t *objects;
    /** Number of objects expected to be in the array */
    uint32_t object_count;
    /** Number of objects actually in the array */
    uint32_t object_count_real;
};

struct empack_str_struct {
    /** Data value, points into the originally supplied Msgpack buffer */
    const char *data;
    /** Expected size of the string buffer */
    uint32_t size;
};

struct empack_bin_struct {
    /** Data value, points into the originally supplied Msgpack buffer */
    const void *data;
    /** Expected size of the buffer */
    uint32_t size;
};

struct empack_ext_struct {
    /** Data value, points into the originally supplied Msgpack buffer */
    const void *data;
    /** Size of the buffer */
    uint32_t size;
    /** Type value for the EXT object */
    uint8_t type;
};

struct empack_obj_struct {
    empack_type_e type;
    union {
        /** Union value valid for all MAP type data */
        empack_map_t map;
        /** Union value valid for all ARRAY type data */
        empack_array_t array;
        /** Union value valid for all STR type data */
        empack_str_t str;
        /** Union value valid for all BIN type data */
        empack_bin_t bin;
        /** Union value valid for all EXT type data */
        empack_ext_t ext;
        float float32;
        double float64;
        uint8_t uint8;
        uint16_t uint16;
        uint32_t uint32;
        uint64_t uint64;
        int8_t int8;
        int16_t int16;
        int32_t int32;
        int64_t int64;
    } val;
    /**
     * If this object is in a MAP or ARRAY, this is a pointer to the parent
     * object. Needed for parsing purposes, and useful for tree traversal after
     * parsing. NULL if no parent is present.
     */
    empack_obj_t *parent;
};

struct empack_map_pair_struct {
    /** Key object for this pair */
    empack_obj_t key;
    /** Value object for this pair */
    empack_obj_t value;
};

enum empack_status_enum {
    /** Parsing is completed with no errors */
    EMPACK_STATUS_COMPLETE = 0,
    /** No errors in parsing, but the Msgpack supplied is incomplete */
    EMPACK_STATUS_WANT_MORE,
    /** Parsing completed, but extra data was supplied and not parsed */
    EMPACK_STATUS_EXTRA,
    /**
     * Ran out of arena memory, the empack->arena_used value will show the
     * amount of memory required to fully parse the supplied Msgpack buffer
     */
    EMPACK_STATUS_NOMEM,
    /** Generic error while parsing */
    EMPACK_STATUS_ERROR,
};

struct empack_struct {
    /** Root object of the Msgpack object tree, filled out during parsing */
    empack_obj_t root;
    /** Memory arena empack can use to construct the object tree */
    void *arena;
    /** Size of the memory arena */
    uint32_t arena_sz;
    /** How much of the memory arena is used */
    uint32_t arena_used;
};

/**
 * Initialize an empack struct, allowing it to be used for parsing. Calling this
 * on a previously initialzed empack struct will effectively reset it.
 *
 * The arena memory supplied must be valid for the entire lifetime of the empack
 * struct.
 *
 * @param empack Empack struct to intialize
 * @param arena Memory arena empack will use for storing Msgpack object tree information
 * @param arena_sz Size of the memory arena
 */
void empack_init(empack_t *empack, void *arena, uint32_t arena_sz);

/**
 * Parse the provided Msgpack data. Note that the resulting object tree in the
 * empack struct may point into the supplied buffer for certain objects such as
 * BIN types.
 *
 * Spec for reference: https://github.com/msgpack/msgpack/blob/master/spec.md
 *
 * @param empack Empack struct, must be initialzed by empack_init
 * @param msgpack Msgpack buffer to parse
 * @param len Size of the Msgpack buffer
 */
empack_status_e empack_parse(empack_t *empack, const void *msgpack, uint32_t len);

/**
 * Parse a singular Msgpack object, useful for use cases where the Msgpack data
 * must be streamed or the caller does not want to allocate a memory arena.
 *
 * Note that for MAP and ARRAY types, the object pointers to child objects will
 * not be allocated and set to NULL.
 *
 * @param object Empack object struct to fill out
 * @param msgpack Msgpack buffer to parse
 * @param len Length of the Msgpack buffer, set on return to the number of bytes
 * processed
 */
empack_status_e empack_parse_one(empack_obj_t *object, const void *msgpack, uint32_t *len);

#endif /* _EMPACK_H_ */