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/*
* transpiler from a catskill intermediate translation unit,
* to the c programming language, as the main translation target.
*
* walks a fully-lowered translation unit and emits (slightly ugly)
* c source code.
*
* Copyright (c) 2025-2026, Mel G. <mel@rnrd.eu>
*
* SPDX-License-Identifier: MPL-2.0
*/
#pragma once
#include "catboot.h"
// the output of the transpilation pass.
// used for both file output and string buffer output.
struct Transpile_Output
{
FILE* file;
struct String_Buffer string;
};
struct Transpile_Output
transpile_output_from_file(FILE* file)
{
check(file != nil, "transpile output file is nil");
return (struct Transpile_Output){
.file = file,
.string = string_buffer_empty(),
};
}
#define TRANSPILE_OUTPUT_MAX_LENGTH 262144 // 256 KiB
struct Transpile_Output
transpile_output_from_string(void)
{
return (struct Transpile_Output){
.file = nil,
.string = string_buffer_new(TRANSPILE_OUTPUT_MAX_LENGTH),
};
}
#define TRANSPILE_OUTPUT_MAX_WRITE_LENGTH 4096
void
transpile_output_write(struct Transpile_Output* output, const ascii* format, ...)
{
va_list args;
va_start(args, format);
if (output->file) {
vfprintf(output->file, format, args);
} else {
ascii buffer[TRANSPILE_OUTPUT_MAX_WRITE_LENGTH];
int written = vsnprintf(buffer, TRANSPILE_OUTPUT_MAX_WRITE_LENGTH, format, args);
check(written >= 0 && (uint)written < TRANSPILE_OUTPUT_MAX_LENGTH,
"transpile output string buffer overflow");
string_buffer_append_c_str(&output->string, buffer);
}
va_end(args);
}
struct String
transpile_output_string(struct Transpile_Output* output)
{
check(output->file == nil, "transpile output is not a string");
return string_buffer_to_string(&output->string);
}
FILE*
transpile_output_file(struct Transpile_Output* output)
{
check(output->file != nil, "transpile output is not a file");
return output->file;
}
struct Transpiler
{
struct Transpile_Output output;
struct Unit* unit;
};
void
transpiler_new(struct Transpiler* transpiler, struct Transpile_Output output)
{
*transpiler = (struct Transpiler){
.output = output,
};
}
#define TRANSPILE_WRITE(...) transpile_output_write(&transpiler->output, __VA_ARGS__)
// emit the forward declaration for a single type.
// TODO: per-kind emission lands in a follow-up commit.
void
transpile_type_forward(struct Transpiler* transpiler, struct Type* type)
{
(void)transpiler;
(void)type;
}
// emit the full definition for a single type.
// TODO: per-kind emission lands in a follow-up commit.
void
transpile_type_definition(struct Transpiler* transpiler, struct Type* type)
{
(void)transpiler;
(void)type;
}
// emit a function signature (used for both forward-decls and the line
// preceding a function body).
// TODO: per-kind emission lands in a follow-up commit.
void
transpile_function_signature(struct Transpiler* transpiler, struct Function* function)
{
(void)transpiler;
(void)function;
}
// emit a function body in the form `signature { block }`.
// TODO: per-kind emission lands in a follow-up commit.
void
transpile_function_body(struct Transpiler* transpiler, struct Function* function)
{
(void)transpiler;
(void)function;
}
// walk a lowered translation unit and emit c source into the transpiler's output.
// the order of the translation unit, and thus the final source output is fixed.
// preamble, then imports, type forwards, type definitions in topological dependency
// order, function forwads, function definitions, and runtime trailer (if main present).
int
transpile_unit(struct Transpiler* transpiler, struct Unit* unit)
{
transpiler->unit = unit;
TRANSPILE_WRITE("#include \"core.c\"\n");
FOR_EACH_ARRAY (struct Import, import, &unit->imports) {
TRANSPILE_WRITE("#include \"%.*s\"\n", (int)import->path.length, import->path.data);
}
FOR_EACH_ARRAY (struct Type*, type_slot, &unit->types.entries) {
transpile_type_forward(transpiler, *type_slot);
}
FOR_EACH_ARRAY (Type_Id, ordered_id, &unit->type_emission_order) {
struct Type* type = *array_at(struct Type*, &unit->types.entries, *ordered_id);
transpile_type_definition(transpiler, type);
}
bool main_takes_args = false;
bool has_main = false;
FOR_EACH_ARRAY (struct Function*, function_slot, &unit->functions.entries) {
struct Function* function = *function_slot;
transpile_function_signature(transpiler, function);
if (function->is_main) {
has_main = true;
main_takes_args = function->main_takes_args;
}
}
FOR_EACH_ARRAY (struct Function*, function_slot, &unit->functions.entries) {
transpile_function_body(transpiler, *function_slot);
}
if (has_main) {
if (main_takes_args) TRANSPILE_WRITE("#define CATSKILL_MAIN_TAKES_ARGS\n");
TRANSPILE_WRITE("#include \"runtime.c\"\n");
}
return 0;
}
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