#ifndef APFL_H
#define APFL_H

#ifdef __cplusplus
extern "C" {
#endif

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

// Allocator

// apfl_allocator_cb is called to (re)allocate and free memory.
//
// If called with newsize = 0, the memory of oldsize bytes pointed to by
// oldptr should be freed. If the NULL-pointer is freed, nothing should
// happen. A freeing must return the NULL-pointer and is not allowed to
// fail.
//
// If oldptr = NULL and oldsize = 0, memory of size newsize should be
// allocated and the pointer to it returned. If the allocation fails, NULL
// should be returned.
//
// Reallocation is done by calling with the old pointer, old size and new
// size. On success the new pointer should be returned and the old pointer
// (unless they're the same) no longer used. On failure, NULL should be
// returned and the oldptr should stay valid.
typedef void * (*apfl_allocator_cb) (void *opaque, void *oldptr, size_t oldsize, size_t newsize);

struct apfl_allocator {
    void *opaque;
    apfl_allocator_cb alloc;
};

struct apfl_allocator apfl_allocator_default(void);
struct apfl_allocator apfl_allocator_wrap_verifying(struct apfl_allocator *wrapped);

typedef double apfl_number;

struct apfl_position {
    int line;
    int col;
};

bool apfl_position_eq(struct apfl_position, struct apfl_position);

// Strings

struct apfl_string_view {
    const char *bytes;
    size_t len;
};

struct apfl_string {
    char *bytes;
    size_t len;

    // TODO: Not sure, if it's a good idea to expose this. We now need the actual
    //       size of the underlying allocation though. Maybe we should better
    //       shrink the cap to len wen we're done building a string?
    size_t cap;
};

#define APFL_STR_FMT "%.*s"
#define APFL_STR_FMT_ARGS(s) (int)(s).len,(s).bytes

struct apfl_string_view apfl_string_view_from_view(struct apfl_string_view);
struct apfl_string_view apfl_string_view_from_cstr(char *);
struct apfl_string_view apfl_string_view_from_const_cstr(const char *);
struct apfl_string_view apfl_string_view_from_string(struct apfl_string);

#define apfl_string_view_from(s) _Generic((s),                        \
    struct apfl_string:      apfl_string_view_from_string,            \
    struct apfl_string_view: apfl_string_view_from_view,              \
    char *:                  apfl_string_view_from_cstr,              \
    const char *:            apfl_string_view_from_const_cstr         \
)(s)

int apfl_string_view_cmp(struct apfl_string_view, struct apfl_string_view);

#define apfl_string_cmp(a, b) apfl_string_view_cmp(apfl_string_view_from(a), apfl_string_view_from(b))
#define apfl_string_eq(a, b) (apfl_string_cmp((a), (b)) == 0)

struct apfl_string apfl_string_blank(void);
void apfl_string_deinit(struct apfl_allocator allocator, struct apfl_string *);
struct apfl_string apfl_string_move(struct apfl_string *src);

/**
 * Copies a string from src to dst. dst must point to a blank string.
 * Returns true on success, false otherwise (if the necessary memory could not
 * be allocated).
 */
bool apfl_string_copy(struct apfl_allocator allocator, struct apfl_string *dst, struct apfl_string_view src);

struct apfl_string_builder {
    struct apfl_allocator allocator;
    char *bytes;
    size_t len;
    size_t cap;
};

void apfl_string_builder_init(struct apfl_allocator allocator, struct apfl_string_builder *);
void apfl_string_builder_deinit(struct apfl_string_builder *);
bool apfl_string_builder_append(struct apfl_string_builder *, struct apfl_string_view);
bool apfl_string_builder_append_byte(struct apfl_string_builder *, char byte);
struct apfl_string apfl_string_builder_move_string(struct apfl_string_builder *);

#define apfl_string_builder_append_cstr(builder, cstr) (apfl_string_builder_append((builder), apfl_string_view_from_cstr((cstr))))

// Tokens

enum apfl_token_type {
    APFL_TOK_LPAREN,
    APFL_TOK_RPAREN,
    APFL_TOK_LBRACKET,
    APFL_TOK_RBRACKET,
    APFL_TOK_LBRACE,
    APFL_TOK_RBRACE,
    APFL_TOK_MAPSTO,
    APFL_TOK_EXPAND,
    APFL_TOK_DOT,
    APFL_TOK_AT,
    APFL_TOK_SEMICOLON,
    APFL_TOK_LINEBREAK,
    APFL_TOK_CONTINUE_LINE,
    APFL_TOK_COMMENT,
    APFL_TOK_COMMA,
    APFL_TOK_QUESTION_MARK,
    APFL_TOK_STRINGIFY,
    APFL_TOK_ASSIGN,
    APFL_TOK_LOCAL_ASSIGN,
    APFL_TOK_NUMBER,
    APFL_TOK_NAME,
    APFL_TOK_STRING,
};

struct apfl_token {
    enum apfl_token_type type;
    struct apfl_position position;
    union {
        struct apfl_string text;
        apfl_number number;
    };
};

void apfl_token_deinit(struct apfl_allocator allocator, struct apfl_token *);

const char *apfl_token_type_name(enum apfl_token_type);

void apfl_token_print(struct apfl_token, FILE *);

// Errors

enum apfl_error_type {
    APFL_ERR_MALLOC_FAILED,
    APFL_ERR_INPUT_ERROR,
    APFL_ERR_UNEXPECTED_EOF,
    APFL_ERR_EXPECTED_EQ_AFTER_COLON,
    APFL_ERR_UNEXPECTED_BYTE,
    APFL_ERR_UNEXPECTED_BYTE_IN_NUMBER,
    APFL_ERR_EXPECTED_DIGIT,
    APFL_ERR_EXPECTED_HEX_IN_HEX_ESCAPE,
    APFL_ERR_INVALID_ESCAPE_SEQUENCE,
    APFL_ERR_NO_LINEBREAK_AFTER_CONTINUE_LINE,
    APFL_ERR_UNEXPECTED_TOKEN,
    APFL_ERR_MISMATCHING_CLOSING_BRACKET,
    APFL_ERR_UNEXPECTED_EOF_AFTER_TOKEN,
    APFL_ERR_STATEMENTS_BEFORE_PARAMETERS,
    APFL_ERR_EMPTY_ASSIGNMENT_BEFORE_PARAMETERS,
    APFL_ERR_UNEXPECTED_EXPRESSION,
    APFL_ERR_INVALID_ASSIGNMENT_LHS,
    APFL_ERR_EMPTY_ASSIGNMENT,
    APFL_ERR_ONLY_ONE_EXPAND_ALLOWED,
    APFL_ERR_UNEXPECTED_CONSTANT_IN_MEMBER_ACCESS,
    APFL_ERR_UNEXPECTED_EXPR_IN_MEMBER_ACCESS,
    APFL_ERR_UNEXPECTED_BLANK_IN_MEMBER_ACCESS,
    APFL_ERR_NOT_IMPLEMENTED,
};

const char *apfl_error_type_name(enum apfl_error_type);

struct apfl_error {
    enum apfl_error_type type;

    // Optional data
    struct apfl_position position;
    struct apfl_position position2;
    enum apfl_token_type token_type;
    enum apfl_token_type token_type2;
    char byte;
};

bool apfl_error_print(struct apfl_error, FILE *);
bool apfl_error_as_string(struct apfl_error, struct apfl_allocator, struct apfl_string *out);

struct apfl_error apfl_error_simple(enum apfl_error_type);
bool apfl_error_is_fatal_type(enum apfl_error_type);

#define APFL_ERROR_IS_FATAL(err) (apfl_error_is_fatal_type((err).type))

enum apfl_expr_type {
    APFL_EXPR_LIST,
    APFL_EXPR_DICT,
    APFL_EXPR_CALL,
    APFL_EXPR_SIMPLE_FUNC,
    APFL_EXPR_COMPLEX_FUNC,
    APFL_EXPR_ASSIGNMENT,
    APFL_EXPR_DOT,
    APFL_EXPR_AT,
    APFL_EXPR_CONSTANT,
    APFL_EXPR_VAR,
    APFL_EXPR_BLANK,
};

struct apfl_expr_list_item {
    struct apfl_expr *expr;
    bool expand;
};

struct apfl_expr_list {
    struct apfl_expr_list_item *items;
    size_t len;
};

struct apfl_expr_dict_pair {
    struct apfl_expr *k;
    struct apfl_expr *v;
};

struct apfl_expr_dict {
    struct apfl_expr_dict_pair *items;
    size_t len;
    size_t cap;
};

struct apfl_expr_call {
    struct apfl_expr *callee;
    struct apfl_expr_list arguments;
};

struct apfl_expr_body {
    struct apfl_expr *items;
    size_t len;
    size_t cap;
};

enum apfl_expr_const_type {
    APFL_EXPR_CONST_NIL,
    APFL_EXPR_CONST_BOOLEAN,
    APFL_EXPR_CONST_STRING,
    APFL_EXPR_CONST_NUMBER,
};

struct apfl_expr_const {
    enum apfl_expr_const_type type;

    union {
        // variant nil is without data
        bool boolean;
        struct apfl_string string;
        apfl_number number;
    };
};

struct apfl_expr_param_predicate {
    struct apfl_expr_param *lhs;
    struct apfl_expr *rhs;
};

enum apfl_expr_param_type {
    APFL_EXPR_PARAM_VAR,
    APFL_EXPR_PARAM_CONSTANT,
    APFL_EXPR_PARAM_PREDICATE,
    APFL_EXPR_PARAM_LIST,
    APFL_EXPR_PARAM_BLANK,
};

struct apfl_expr_params {
    struct apfl_expr_params_item *params;
    size_t len;
    size_t cap;
};

struct apfl_expr_param {
    enum apfl_expr_param_type type;

    union {
        struct apfl_string var;
        struct apfl_expr_const constant;
        struct apfl_expr_param_predicate predicate;
        struct apfl_expr_params list;
    };
};

struct apfl_expr_params_item {
    bool expand;
    struct apfl_expr_param param;
};

struct apfl_expr_subfunc {
    struct apfl_expr_params params;
    struct apfl_expr_body body;
};

struct apfl_expr_complex_func {
    struct apfl_expr_subfunc *subfuncs;
    size_t len;
    size_t cap;
};

enum apfl_expr_assignable_type {
    APFL_EXPR_ASSIGNABLE_VAR_OR_MEMBER,
    APFL_EXPR_ASSIGNABLE_CONSTANT,
    APFL_EXPR_ASSIGNABLE_PREDICATE,
    APFL_EXPR_ASSIGNABLE_LIST,
    APFL_EXPR_ASSIGNABLE_BLANK,

};

enum apfl_expr_assignable_var_or_member_type {
    APFL_EXPR_ASSIGNABLE_VAR_OR_MEMBER_VAR,
    APFL_EXPR_ASSIGNABLE_VAR_OR_MEMBER_DOT,
    APFL_EXPR_ASSIGNABLE_VAR_OR_MEMBER_AT,
};

struct apfl_expr_assignable_var_or_member_dot {
    struct apfl_expr_assignable_var_or_member *lhs;
    struct apfl_string rhs;
};
struct apfl_expr_assignable_var_or_member_at {
    struct apfl_expr_assignable_var_or_member *lhs;
    struct apfl_expr *rhs;
};

struct apfl_expr_assignable_var_or_member {
    enum apfl_expr_assignable_var_or_member_type type;

    union {
        struct apfl_string var;
        struct apfl_expr_assignable_var_or_member_dot dot;
        struct apfl_expr_assignable_var_or_member_at at;
    };
};

struct apfl_expr_assignable_predicate {
    struct apfl_expr_assignable *lhs;
    struct apfl_expr *rhs;
};
struct apfl_expr_assignable_list {
    struct apfl_expr_assignable_list_item *items;
    size_t len;
};

struct apfl_expr_assignable {
    enum apfl_expr_assignable_type type;

    union {
        struct apfl_expr_assignable_var_or_member var_or_member;
        struct apfl_expr_const constant;
        struct apfl_expr_assignable_predicate predicate;
        struct apfl_expr_assignable_list list;
    };
};

struct apfl_expr_assignable_list_item {
    struct apfl_expr_assignable assignable;
    bool expand;
};

struct apfl_expr_assignment {
    bool local;
    struct apfl_expr_assignable lhs;
    struct apfl_expr *rhs;
};

struct apfl_expr_dot {
    struct apfl_expr *lhs;
    struct apfl_string rhs;
};

struct apfl_expr_at {
    struct apfl_expr *lhs;
    struct apfl_expr *rhs;
};

struct apfl_expr {
    enum apfl_expr_type type;

    union {
        struct apfl_expr_list list;
        struct apfl_expr_dict dict;
        struct apfl_expr_call call;
        struct apfl_expr_body simple_func;
        struct apfl_expr_complex_func complex_func;
        struct apfl_expr_assignment assignment;
        struct apfl_expr_dot dot;
        struct apfl_expr_at at;
        struct apfl_expr_const constant;
        struct apfl_string var;
        // blank has no further data
    };

    struct apfl_position position;
};

void apfl_expr_print(struct apfl_expr, FILE *);

bool apfl_expr_eq(struct apfl_expr, struct apfl_expr);

// Begin deinit functions

void apfl_expr_deinit(struct apfl_allocator allocator, struct apfl_expr *);
void apfl_expr_list_deinit(struct apfl_allocator allocator, struct apfl_expr_list *);
void apfl_expr_list_item_deinit(struct apfl_allocator allocator, struct apfl_expr_list_item *);
void apfl_expr_dict_pair_deinit(struct apfl_allocator allocator, struct apfl_expr_dict_pair *);
void apfl_expr_dict_deinit(struct apfl_allocator allocator, struct apfl_expr_dict *);
void apfl_expr_call_deinit(struct apfl_allocator allocator, struct apfl_expr_call *);
void apfl_expr_body_deinit(struct apfl_allocator allocator, struct apfl_expr_body *);
void apfl_expr_const_deinit(struct apfl_allocator allocator, struct apfl_expr_const *);
void apfl_expr_param_predicate_deinit(struct apfl_allocator allocator, struct apfl_expr_param_predicate *);
void apfl_expr_params_deinit(struct apfl_allocator allocator, struct apfl_expr_params *);
void apfl_expr_params_item_deinit(struct apfl_allocator allocator, struct apfl_expr_params_item *);
void apfl_expr_param_deinit(struct apfl_allocator allocator, struct apfl_expr_param *);
void apfl_expr_subfunc_deinit(struct apfl_allocator allocator, struct apfl_expr_subfunc *);
void apfl_expr_complex_func_deinit(struct apfl_allocator allocator, struct apfl_expr_complex_func *);
void apfl_expr_assignable_predicate_deinit(struct apfl_allocator allocator, struct apfl_expr_assignable_predicate *);
void apfl_expr_assignable_list_item_deinit(struct apfl_allocator allocator, struct apfl_expr_assignable_list_item *);
void apfl_expr_assignable_list_deinit(struct apfl_allocator allocator, struct apfl_expr_assignable_list *);
void apfl_expr_assignable_var_or_member_dot_deinit(struct apfl_allocator allocator, struct apfl_expr_assignable_var_or_member_dot *);
void apfl_expr_assignable_var_or_member_at_deinit(struct apfl_allocator allocator, struct apfl_expr_assignable_var_or_member_at *);
void apfl_expr_assignable_var_or_member_deinit(struct apfl_allocator allocator, struct apfl_expr_assignable_var_or_member *);
void apfl_expr_assignable_deinit(struct apfl_allocator allocator, struct apfl_expr_assignable *);
void apfl_expr_assignment_deinit(struct apfl_allocator allocator, struct apfl_expr_assignment *);
void apfl_expr_dot_deinit(struct apfl_allocator allocator, struct apfl_expr_dot *);
void apfl_expr_at_deinit(struct apfl_allocator allocator, struct apfl_expr_at *);

// End deinit functions

// Begin move functions

struct apfl_expr                          apfl_expr_move(struct apfl_expr *);
struct apfl_expr_list                     apfl_expr_list_move(struct apfl_expr_list *);
struct apfl_expr_list_item                apfl_expr_list_item_move(struct apfl_expr_list_item *);
struct apfl_expr_dict_pair                apfl_expr_dict_pair_move(struct apfl_expr_dict_pair *);
struct apfl_expr_dict                     apfl_expr_dict_move(struct apfl_expr_dict *);
struct apfl_expr_call                     apfl_expr_call_move(struct apfl_expr_call *);
struct apfl_expr_body                     apfl_expr_body_move(struct apfl_expr_body *);
struct apfl_expr_const                    apfl_expr_const_move(struct apfl_expr_const *);
struct apfl_expr_param_predicate          apfl_expr_param_predicate_move(struct apfl_expr_param_predicate *);
struct apfl_expr_params                   apfl_expr_params_move(struct apfl_expr_params *);
struct apfl_expr_param                    apfl_expr_param_move(struct apfl_expr_param *);
struct apfl_expr_subfunc                  apfl_expr_subfunc_move(struct apfl_expr_subfunc *);
struct apfl_expr_complex_func             apfl_expr_complex_func_move(struct apfl_expr_complex_func *);
struct apfl_expr_assignable_var_or_member apfl_expr_assignable_var_or_member_move(struct apfl_expr_assignable_var_or_member *);
struct apfl_expr_assignable_predicate     apfl_expr_assignable_predicate_move(struct apfl_expr_assignable_predicate *);
struct apfl_expr_assignable_dot           apfl_expr_assignable_dot_move(struct apfl_expr_assignable_dot *);
struct apfl_expr_assignable_at            apfl_expr_assignable_at_move(struct apfl_expr_assignable_at *);
struct apfl_expr_assignable_list          apfl_expr_assignable_list_move(struct apfl_expr_assignable_list *);
struct apfl_expr_assignable               apfl_expr_assignable_move(struct apfl_expr_assignable *);
struct apfl_expr_assignment               apfl_expr_assignment_move(struct apfl_expr_assignment *);
struct apfl_expr_dot                      apfl_expr_dot_move(struct apfl_expr_dot *);
struct apfl_expr_at                       apfl_expr_at_move(struct apfl_expr_at *);

// End move functions

enum apfl_parse_result {
    APFL_PARSE_OK,
    APFL_PARSE_EOF,
    APFL_PARSE_ERROR,
};

struct apfl_tokenizer;

typedef struct apfl_tokenizer *apfl_tokenizer_ptr;

/* An apfl_source_reader is used to read source code for parsing / evaluation.
 */
struct apfl_source_reader {
    /* callback gets called repeatedly to get the source code.
     * buf points to a buffer to fill that has a size of *len.
     * The callback must set len to the number of read bytes and return true
     * on success and false on failure.
     *
     * Setting len to 0 indicates and end of file.
     *
     * need is true if more input is required for parsing, this is useful for
     * implementing a reader for a REPL to indicate to the user if they need
     * to type more code (e.g. by changing the prompt).
     */
    bool (*callback)(void *opaque, char *buf, size_t *len, bool need);

    void *opaque;
};

apfl_tokenizer_ptr apfl_tokenizer_new(struct apfl_allocator allocator, struct apfl_source_reader);

void apfl_tokenizer_destroy(apfl_tokenizer_ptr);

enum apfl_parse_result apfl_tokenizer_next(apfl_tokenizer_ptr, bool need);

/* Get the current token.
 * Return value is undefined when the last call to apfl_tokenizer_next did not
 * return APFL_PARSE_OK.
 */
struct apfl_token apfl_tokenizer_get_token(apfl_tokenizer_ptr);

/* Get the current error.
 * Return value is undefined when the last call to apfl_tokenizer_next did not
 * return APFL_PARSE_ERROR.
 */
struct apfl_error apfl_tokenizer_get_error(apfl_tokenizer_ptr);

/* apfl_string_source_reader_* implements an apfl_source_reader that reads
 * source code from a string view.
 */
struct apfl_string_source_reader_data {
    struct apfl_string_view sv;
    size_t off;
};

struct apfl_string_source_reader_data apfl_string_source_reader_create(struct apfl_string_view);

/* Creates a source reader for apfl_string_source_reader_data.
 * The pointed to apfl_string_source_reader_data and the underlying string view
 * must be alive while the reader is in use.
 */
struct apfl_source_reader apfl_string_source_reader(struct apfl_string_source_reader_data *);

struct apfl_parser_token_source {
    enum apfl_parse_result (*next)(void *, bool need);
    struct apfl_token (*get_token)(void *);
    struct apfl_error (*get_error)(void *);
    void *opaque;
};

struct apfl_parser_token_source apfl_tokenizer_as_token_source(apfl_tokenizer_ptr);

struct apfl_parser;

typedef struct apfl_parser *apfl_parser_ptr;

apfl_parser_ptr apfl_parser_new(struct apfl_allocator allocator, struct apfl_parser_token_source);

/* Destroys the parser.
 * Note that if the token source needs it's own destruction, you'll have to do
 * that yourself after destroying the parser.
 */
void apfl_parser_destroy(apfl_parser_ptr);

enum apfl_parse_result apfl_parser_next(apfl_parser_ptr);

/* Get the current error.
 * Return value is undefined when the last call to apfl_parser_next did not
 * return APFL_PARSE_ERROR.
 */
struct apfl_error apfl_parser_get_error(apfl_parser_ptr);

/* Get the current expression.
 * Return value is undefined when the last call to apfl_parser_next did not
 * return APFL_PARSE_OK.
 */
struct apfl_expr apfl_parser_get_expr(apfl_parser_ptr);

struct apfl_ctx_data;
typedef struct apfl_ctx_data *apfl_ctx;

enum apfl_value_type {
    APFL_VALUE_NIL,
    APFL_VALUE_BOOLEAN,
    APFL_VALUE_NUMBER,
    APFL_VALUE_STRING,
    APFL_VALUE_LIST,
    APFL_VALUE_DICT,
    APFL_VALUE_FUNC,
};

typedef int apfl_stackidx;

enum apfl_result {
    APFL_RESULT_OK, // Evaluation succeeded, value is on the stack

    // TODO: No further details are yet provided on (fatal) error. Not quite
    //       sure what to return / how errors/exceptions should work. Maybe a
    //       value + a backtrace?
    APFL_RESULT_ERR,
    APFL_RESULT_ERR_FATAL,
};

apfl_ctx apfl_ctx_new(struct apfl_allocator);

void apfl_ctx_destroy(apfl_ctx);

typedef struct apfl_iterative_runner_data *apfl_iterative_runner;

apfl_iterative_runner apfl_iterative_runner_new(apfl_ctx, struct apfl_source_reader);
bool apfl_iterative_runner_next(apfl_iterative_runner);
enum apfl_result apfl_iterative_runner_get_result(apfl_iterative_runner);
void apfl_iterative_runner_destroy(apfl_iterative_runner);

// Get the type of a value on the stack
enum apfl_value_type apfl_get_type(apfl_ctx, apfl_stackidx);

// Create a new empty list on the stack
enum apfl_result apfl_list_create(apfl_ctx, size_t initial_capacity);
// Append a value to a list. The value will be dropped.
enum apfl_result apfl_list_append(apfl_ctx, apfl_stackidx list, apfl_stackidx value);
// Append a list to another list. The second list will be dropped.
enum apfl_result apfl_list_append_list(apfl_ctx, apfl_stackidx a, apfl_stackidx b);
// Create a new empty dict on the stack
enum apfl_result apfl_dict_create(apfl_ctx);
// Set a value in a dictionary. k and v will be dropped.
enum apfl_result apfl_dict_set(apfl_ctx, apfl_stackidx dict, apfl_stackidx k, apfl_stackidx v);
// Get a value from a container (list or dict) and push it on the stack. container and k will be dropped.
enum apfl_result apfl_get_member(apfl_ctx, apfl_stackidx container, apfl_stackidx k);

void apfl_debug_print_val(apfl_ctx, apfl_stackidx, FILE *);

#ifdef __cplusplus
}
#endif

#endif