#pragma once
#include "stddef.h"

/**
 * Represents the natively defined type of integers
 */
#define INK_INTEGER 0

/**
 * Represents the natively defined type of natively defined functions
 */
#define INK_NATIVE_FUNCTION 1

/**
 * Represents the natively defined type of functions defined from within ink
 */
#define INK_FUNCTION 2

/**
 * Represents the special coroutine state that means that it was disposed of and is ready for reuse
 */
#define INK_ROUTINE_CAN_REUSE 32

/**
 * Represents the special coroutine state that means that it was terminated without errors
 */
#define INK_ROUTINE_SUCCESS 1

#ifdef __cplusplus
extern "C" {
#endif

/**
 * Represents arbitrary values within ink
 */
struct elem {
	int type;
	int value;
};

/**
 * Represents a stack-frame within the execution context
 */
struct stack_frame {
	struct elem executing;
	int index;
};

/**
 * Represents a function within ink, defined in ink, using the homoiconic representation of ink
 */
struct fn {
	char *name;
	struct elem *things;
	int size;
};

struct context;

/**
 * Represents natively defined words within ink
 */
struct native_fn {
	char *name;
	void (*value)(struct context *);
};

/**
 * Represents the narrow execution context of a single thread of execution within ink.
 */
struct ink_routine {
	int panic;
	
	struct elem *stack;
	int capacity;
	int top;
	
	struct stack_frame *function_stack;
	int function_stack_capacity;
	int function_stack_top;

    /**
     * This user data can be set to any value convenient for the user to track a state local to the routine that is executing
     */
	void *routine_userdata;
};

/**
 * Represents a complete execution context for the ink interpreter
 */
struct context {
	int panic;

    void *(*inner_malloc)(size_t);
    void *(*inner_realloc)(void *, size_t);
    void (*inner_free)(void *);

    void *(*malloc)(size_t);
    void *(*realloc)(void *, size_t);
    void (*free)(void *);
	int (*putchar)(int);
	
	struct ink_routine *routines;
	int routines_capacity;
	int routines_top;

    /**
     * Contains the id of the routine that is currently being manipulated
     */
	int routine_current;
	
	struct native_fn *native_words;
	int native_words_capacity;
	int native_words_top;
	
	struct fn *words;
	int words_capacity;
	int words_top;
	
	char **lex_reserved_words;
	int lex_reserved_words_capacity;
	int lex_reserved_words_top;
	
	unsigned int steps;

    /**
     * Can be set to any data that is convenient to the user to track and use within natively defined functions
     */
	void *persistent_userdata;
};

/**
 * Creates a routine to execute within the context
 * @param ctx The context in which to create the routine
 * @warning Does not set the `routine_current` of the context to the newly created routine
 * @return either a negative error value or the id of the created routine
 */
int ink_make_routine(struct context *ctx);

/**
 * Cleans the targeted routine id data from the context
 * @param ctx The context to operate in
 * @param routine The id of the routine to destroy
 * @return 0 if nothing could or needed to be performed, 1 otherwise
 */
int ink_kill_routine(struct context *ctx, int routine);

/**
 * Declares and defines a native function within the context
 * @param ctx The context tpo operate in
 * @param name The name to give to the newly declared word
 * @param value A pointer to a valid word-function
 * @return a negative value in case of error, 0 otherwise
 */
int ink_add_native(struct context *ctx, const char *name, void(*value)(struct context *));

/**
 * Pushes a value on the current routine's value stack
 * @param ctx The context to manipulate
 * @param value The value to push
 * @return 0 on success, a negative value on failure
 */
int ink_push(struct context *ctx, struct elem value);

/**
 * Pushes a function on the execution stack of the current routine of the context
 * @param ctx The context to operate in
 * @param value the function that will be pushed. in the state one wants it to run from
 * @return 0 on success, a negative value on failure
 */
int ink_push_fn(struct context *ctx, struct stack_frame value);

/**
 * Create a context to execute routines
 * @param malloc the memory allocation function, with a signature similar to the standard malloc
 * @param realloc the memory allocation function, with a signature similar to the standard realloc
 * @param free the memory allocation function, with a signature similar to the standard free
 * @param putchar a function to print to the output character by character
 * @return a pointer to a context allocated within the malloc function itself.
 */
struct context* ink_make_context(void *(*malloc)(size_t), void *(*realloc)(void *, size_t), void(*free)(void *), int(*putchar)(int));

#ifndef NOSTDLIB
/**
 * Creates a context that includes the standard library of ink, as well as uses the C standard library to operate
 * @return a pointer to a context allocated with malloc and with predefined functions added
 */
struct context* ink_make_default_context();
#endif

/**
 * Steps the current routine by one execution step
 * @param pContext The context of the routine to advance
 * @return A negative value in case of error, 0 if execution is finished, a positive value if more steps are required to execute
 */
int ink_step(struct context *pContext);

/**
 * Examine the context to see if any routines can execute
 * @param pContext the context
 * @return 0 if no coroutines are available, 1 otherwise
 */
int ink_can_run(struct context *pContext);

/**
 * Step every routine that can be executed.
 * @param pContext The context, the `routine_current` value may be modified.
 * @return 0
 */
int ink_step_everyone(struct context *pContext);

/**
 * Compiles the code and starts a main routine to execute it
 * @param pContext The context to execute the code in
 * @param buffer The buffer that contains the source as a NULL terminated string
 */
void ink_compile(struct context *pContext, char *buffer);

/**
 * Includes the standard library in the specified context
 * @param ctx The context
 * @return 0
 */
int ink_std_library(struct context *ctx);

/**
 * Removes the top element of the function stack of the current routine of the specified context
 * @param ctx the context
 */
void ink_pop_fn(struct context *ctx);

/**
 * Removes the top element of the stack of the current routine of the specified context
 * @param ctx the context
 */
void ink_pop(struct context *ctx);

#ifdef __cplusplus
};
#endif