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#ifndef LIBQMSK_ERROR_H

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#define LIBQMSK_ERROR_H

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/**

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 * @file

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 *

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 * Support for error handling, using explicit function return codes and error info contexts.

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 *

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 * This is designed to support multiple "namespaces" of errors, which are entirely independent of eachother. These

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 * namespaces can then reference one another, to build a 'tree' of useable error codes. Hence, each 'level' of this

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 * tree has it's own set of error codes, and then error info contexts contain a stack of these error codes, which can

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 * then be used to trace the error down.

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 */

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/**

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 * The type used to represent a scalar error code, there are only unique per level.

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 *

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 * Note that this type is signed to avoid nastyness with negating error codes, but all valid ERR_* codes are *always*

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 * greater than zero in value.

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 */

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typedef signed short err_t;

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/** 

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 * Standardized err_t code to mean no error, evaluates as logical false.

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 */

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static const err_t SUCCESS = 0;

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/**

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 * Extra information about an error, used to reference error codes in external libraries etc.

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 */

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union error_extra {

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    /** (signed) integer code */

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    int int_;

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    /** Constant string */

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    const char *str;

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};

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/**

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 * Errors can contain 'extra' information to reference things like error codes from external libraries; when these are

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 * used, a 'type' must be specified to handle these.

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 */

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struct error_extra_type {

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    /** Short name */

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    const char *name;

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    /** Conversion func, must return a static pointer */

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    const char * (*msg_func) (const struct error_extra_type *type, const union error_extra *extra);

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};

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/**

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 * error_extra_type for libc errno values

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 */

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const struct error_extra_type error_extra_errno;

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/**

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 * error_extra_type for string error values

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 */

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const struct error_extra_type error_extra_string;

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/**

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 * Description of an error code

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 */

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struct error_type {

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    /** The actual code */

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    err_t code;

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    /** The short name of the error */

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    const char *name;

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    /** The type of any contained extra info */

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    const struct error_extra_type *extra_type;

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    /** Any linked error_code table for looking up sub-errors */

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    const struct error_list *sublist;

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};

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/**

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 * Helper macros to define error_type's

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 */

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#define ERROR_TYPE(code, name) \

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    { (code), (name), NULL, NULL }

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#define ERROR_TYPE_ERRNO(code, name) \

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    { (code), (name), &error_extra_errno, NULL }

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#define ERROR_TYPE_STRING(code, name) \

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    { (code), (name), &error_extra_string, NULL }

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#define ERROR_TYPE_CUSTOM(code, name, type) \

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    { (code), (name), (type), NULL }

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#define ERROR_TYPE_SUB(code, name, sub) \

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    { (code), (name), NULL, (sub) }

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#define ERROR_TYPE_END \

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    { 0, NULL, NULL, NULL }

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/**

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 * List of error types

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 */

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struct error_list {

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    /** Name of sublib */

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    const char *name;

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    /** The list */

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    struct error_type list[];

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};

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/**

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 * Helper macro to define an error_list

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 */

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#define ERROR_LIST(name, ...) \

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    { (name), __VA_ARGS__, ERROR_TYPE_END }

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/**

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 * Maximum number of nesting levels supported for errors

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 */

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#define ERROR_DEPTH_MAX 8

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/**

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 * Information about an actual error

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 */

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typedef struct error_state {

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    /** The stack of error codes */

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    struct error_item {

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        /** This level's error code */

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        err_t code;

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        /** Optional table for interpreting error_code, can be used instead of error_code::next */

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        const struct error_list *list;

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    } stack[ERROR_DEPTH_MAX];

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    /** Current top of stack for accumulating errors, NULL means empty stack */

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    /** Type info for external error info */

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    const struct error_extra_type *extra_type;

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    /** Value of external error info */

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    union error_extra extra_value;

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} error_t;

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/**

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 * Look up the error_type for the given table and scalar code.

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 */

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const struct error_type* error_lookup_code (const struct error_list *list, err_t code);

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/**

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 * Look up the error_type for for the given root table and error_info.

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 */

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const struct error_type* error_lookup (const error_t *err);

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/**

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 */

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/**

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 * Maximum length of messages returned by error_msg

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 */

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#define ERROR_MSG_MAX 1024

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/**

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 * Return a pointer to a statically allocated string describing the given full error

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 */

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const char* error_msg (const error_t *err);

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/**

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 * Compare the given errors for equivalency

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 */

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bool error_cmp_eq (const error_t *a, const error_t *b);

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/**

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 */

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/**

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 * Evaluates to the current top of the error stack, 

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 */

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{

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    return err->cur ? err->cur : err->stack;

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}

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/**

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 * Evaluate to the most recent error code pushed, or SUCCESS if none

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 */

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static inline err_t error_code (error_t *err)

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{

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    return err->cur ? err->cur->code : SUCCESS;

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}

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/**

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 * Reset the error state, push the given initial err.

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 */

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void error_set (error_t *err, const struct error_list *list, err_t code);

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/**

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 * Reset, push err, and set extra.

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 */

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void error_set_extra (error_t *err, const struct error_list *list, err_t code, const struct error_extra_type *type, union error_extra extra);

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/**

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 * Push an additional level of error info onto the error state's stack. If it doesn't fit, XXX: it is ignored.

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 */

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void error_push (error_t *err, const struct error_list *list, err_t code);

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/**

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 * Copy value of error

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 */

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void error_copy (error_t *dst, const error_t *src);

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/** Evalutes to the lvalue representing the error code at the top of the stack */

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#define ERROR_CODE(err_state) \

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    (error_top(err_state)->code)

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/** Push a new error code onto the given state */

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#define PUSH_ERROR(err_state, err_list, err_code) ({ \

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        error_push(err_state, err_list, err_code); \

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        err_code; })

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/** Set the error to the given value */

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#define SET_ERROR(err_state, err_list, err_code) ({ \

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        error_set(err_state, err_list, err_code); \

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        err_code; })

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/* Helper macro to use error_set_extra */

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#define _ERROR_SET_EXTRA(err_state, err_list, err_code, err_extra_type, _err_extra_field_, err_extra_value) \

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        error_set_extra(err_state, err_list, err_code, err_extra_type, ((union error_extra) { ._err_extra_field_ = (err_extra_value)}))

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/** Set the error with extra info as integer */

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#define SET_ERROR_EXTRA(err_state, err_list, err_code, err_extra_type, err_extra_int) ({ \

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        _ERROR_SET_EXTRA(err_state, err_list, err_code, err_extra_type, int_, err_extra);  \

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        err_code; })

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/** Set the error with extra info as the libc errno */

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#define SET_ERROR_ERRNO(err_state, err_list, err_code) ({ \

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        _ERROR_SET_EXTRA(err_state, err_list, err_code, &error_extra_errno, int_, errno); \

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        err_code; })

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/** Set the error with extra info as the given static string */

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#define SET_ERROR_STR(err_state, err_list, err_code, err_str) ({ \

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        _ERROR_SET_EXTRA(err_state, err_list, err_code, &error_extra_string, str, err_str); \

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        err_code; })

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/** Set the error with the contents of the given error */

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#define SET_ERROR_COPY(err_state_dst, err_state_src) ({ \

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        error_code(err_state_dst); })

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/** Same as above, but also do a 'goto error' jump */

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#define JUMP_PUSH_ERROR(...)        do { PUSH_ERROR(__VA_ARGS__);       goto error; } while (0)

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#define JUMP_SET_ERROR(...)         do { SET_ERROR(__VA_ARGS__);        goto error; } while (0)

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#define JUMP_SET_ERROR_EXTRA(...)   do { SET_ERROR_EXTRA(__VA_ARGS__);  goto error; } while (0)

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#define JUMP_SET_ERROR_ERRNO(...)   do { SET_ERROR_ERRNO(__VA_ARGS__);  goto error; } while (0)

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#define JUMP_SET_ERROR_STR(...)     do { SET_ERROR_STR(__VA_ARGS__);    goto error; } while (0)

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#define JUMP_SET_ERROR_INFO(...)    do { SET_ERROR_INFO(__VA_ARGS__);   goto error; } while (0)

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/**

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 * Abort execution of process with error message

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 */

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void _error_abort (const char *file, const char *line, const char *func, const char *fmt, ...);

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#define error_abort(...) _error_abort(__FILE__, __LINE__, __func__, __VA_ARGS__);

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/**

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 * Used to mark unexpcted conditions for switch-default. The given val must be an integer, as passed to switch

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 */

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#define NOT_REACHED(val) error_abort("%s = %#x", #val, (int) (val));

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#endif /* LIBQMSK_ERROR_H */