/**
 * @file json.h
 * @brief Minimal JSON reader, internal to this library.
 *
 * Read-only, allocation-per-node, no streaming and no writer. It is here
 * because C ships no JSON parser and the shapes this client has to read are
 * small and fixed. It handles the whole grammar it is fed: UTF-8 throughout,
 * `\uXXXX` escapes with surrogate pairs, and the full number syntax.
 */
#ifndef CEPIS_JSON_H
#define CEPIS_JSON_H

#include <stdbool.h>
#include <stddef.h>

/** Deepest nesting accepted, so a hostile body cannot exhaust the stack. */
#define JSON_MAX_DEPTH 64

/** Kind of a ::json_value_t. */
typedef enum json_type {
        JSON_NULL,
        JSON_BOOL,
        JSON_NUMBER,
        JSON_STRING,
        JSON_ARRAY,
        JSON_OBJECT
} json_type_t;

typedef struct json_value json_value_t;

/** A parsed JSON value. Owns everything it points at. */
struct json_value {
        json_type_t type;
        union {
                bool boolean;
                double number;
                /** NUL-terminated UTF-8, escapes already decoded. */
                char *string;
                struct {
                        json_value_t **items;
                        size_t count;
                } array;
                struct {
                        char **keys;
                        json_value_t **values;
                        size_t count;
                } object;
        } as;
};

/**
 * @brief Parse @p len bytes of JSON.
 * @return The root value, owned by the caller, or `NULL` when @p text is not
 *         one complete JSON value followed only by whitespace.
 */
json_value_t *json_parse(const char *text, size_t len);

/** @brief Release a value and everything below it. `NULL` is ignored. */
void json_free(json_value_t *value);

/**
 * @brief Look a key up in an object.
 * @return The member, borrowed from @p object, or `NULL` when @p object is not
 *         an object or has no such key. The first match wins.
 */
const json_value_t *json_object_get(const json_value_t *object,
                                    const char *key);

/** @brief The string a value holds, or `NULL` when it is not a string. */
const char *json_as_string(const json_value_t *value);

/**
 * @brief Read a value as a number, accepting a numeric string.
 * @return `false` when the value is absent or cannot be read as a number, in
 *         which case @p out is untouched.
 */
bool json_as_double(const json_value_t *value, double *out);

/** @brief Like ::json_as_double, truncating towards zero. */
bool json_as_llong(const json_value_t *value, long long *out);

#endif