/* Copyright (c) 2024 Freya Murphy */

#ifndef __GEN_H__
#define __GEN_H__

#include <mlimits.h>
#include <mips.h>
#include <stdint.h>

#include "parse.h"
#include "tab.h"

// predefine
struct generator;

///
/// a section
///
struct section {
	// name
	struct string name;

	// alignment
	size_t align;

	// data
	char *data;
	size_t len;
	size_t size;

	// permissions
	bool read;
	bool write;
	bool execute;

	/// reference table
	struct reference_table reftab;
};

/* get a section from the generator by name, and return it into res. if the
 * section does not exist, one will be created. */
int gen_get_section(struct generator *gen, struct section **res,
		struct string *name);

/* initalize a section */
int section_init(struct section *section, struct string *name);

/* free a section */
void section_free(struct section *section);

/* extend a section by space bytes plus alignment */
int section_extend(struct section *section, size_t space);

/* push data into a section */
int section_push(struct section *section, void *data, size_t len);

/* push zeros (empty space) to a section */
int section_zero(struct section *section, size_t len);

///
/// instruction generation state
///

struct gen_ins_state {
	// rd,rs,rt
	enum mips32_register rd;
	enum mips32_register rs;
	enum mips32_register rt;

	// fs,ft
	enum mips32_fp_register fs;
	enum mips32_fp_register ft;
	enum mips32_fp_register fd;

	// immd
	uint16_t immd;

	// cc
	uint16_t cc;

	// code
	uint32_t code;

	// pos
	uint32_t pos;

	// size
	uint32_t size;

	// hint
	uint32_t hint;

	// hazard barrier
	bool hb; // 1 bit - 1

	// target
	uint32_t target;

	// index(base)
	// offset(base)
	uint32_t index;
	uint16_t offset;
	enum mips32_register base;

	// current referencd label
	struct string *label;
};

struct gen_ins_override {
	enum mips32_register reg;
	enum mips32_fp_register fpreg;
	uint32_t immd;
};

enum grammer_type {
	// registers
	GMR_RD,
	GMR_RS,
	GMR_RT,
	// fp registers
	GMR_FS,
	GMR_FT,
	GMR_FD,
	// numeric fields
	GMR_IMMD,
	GMR_CC,
	GMR_CODE,
	GMR_POS,
	GMR_SIZE,
	GMR_HB,
	GMR_HINT,
	// addresses
	GMR_HI,
	GMR_LO,
	GMR_TARGET,
	GMR_OFFSET,
	GMR_INDEX_BASE,
	GMR_OFFSET_BASE,
	// len
	__GMR_LEN
};

/* Parses the input string and matches it to a grammer type. Returns
 * the number of characters consumed, or -1 on error.
 */
int gen_parse_grammer_type(const char *name, enum grammer_type *res);

/* Parses a register name, returing 0 on success, 1 on error*/
int gen_parse_register(enum mips32_register *reg, struct string *name);

/* Parses a floating point register name, returing 0 on success, 1 on error*/
int gen_parse_fp_register(enum mips32_fp_register *reg, struct string *name);

/* Parses the overide expression (after the =) in the dsl for the grammer.
 * returns the number of characters consumed, or -1 on error. */
int gen_parse_grammer_overide(struct gen_ins_state *state,
	struct gen_ins_override *over, char *value);

/* Given a grammer for an instruction, read all args as values into the
 * instruction generator state. */
int gen_read_grammer_state(struct generator *gen,
			   struct expr *const expr,
			   struct gen_ins_state *state,
			   struct mips32_grammer *grammer);

/* Given a grammer for an instruction, and a read state, output multiple
 * instructions into the current section in the generator. note:
 * this write_grammer is different from the read grammer such that
 * it supports paramater reassignment and overides. */
int gen_write_grammer_state(struct generator *gen,
			    struct gen_ins_state *state,
			    char *write_grammer);

///
/// generates assembley
/// from a parser stream
///
struct generator {
	struct parser parser;

	// current instruction table
	size_t instructions_len;
	union mips32_instruction *instructions;

	// current grammer table
	size_t grammers_len;
	struct mips32_grammer *grammers;

	// segments
	size_t sections_len;
	size_t sections_size;
	struct section *sections;

	// current section
	struct section *current;

	// symbol table
	struct symbol_table symtab;
};

/* output the source code lines for a provided expression */
void gen_output_expr(struct generator *gen, struct expr *expr);

/* generate the input as mips32r6 */
int generate_mips32r6(struct generator *gen);
/* run codegen with the mips32r2 specification */
int generate_mips32r2(struct generator *gen);
/* run codegen with the mips32r6 specification */
int generate_mips1(struct generator *gen);

/* initalize a generator */
int generator_init(const char *file, struct generator *gen);

/* free a generator */
void generator_free(struct generator *gen);

#endif /* __GEN_H__ */