package translatec

// translatec renders a parsed C header (cimport.Result) as native brolang (.bro)
// source — the offline counterpart to the in-memory `native :: import "x.h"`
// path. The type spellings here MUST mirror loader.translate_c_type so the
// emitted source re-parses to the same types the in-memory import produces; the
// round-trip parser test (compiler_tests.odin) guards that invariant.
//
// Constructs with no hand-writable brolang spelling — C unions, external
// variables, static inline functions, and otherwise unsupported declarations —
// are emitted as `# unsupported in bindings:` comments rather than dropped, so
// the output is an honest record of the whole header.

import "../cimport"
import "core:fmt"
import "core:mem"
import "core:strings"

emit :: proc(result: ^cimport.Result, header: string, allocator := context.allocator) -> string {
	b := strings.builder_make(allocator)
	fmt.sbprintf(&b, "# generated by brolang translate-c from %s\n\n", header)

	record_names := record_name_table(result, allocator)
	defer delete(record_names, allocator)

	emit_records(&b, result, record_names)
	emit_aliases(&b, result, record_names)
	emit_macros(&b, result, record_names)
	emit_functions(&b, result, record_names)
	emit_variables(&b, result)
	emit_unsupported(&b, result)

	return strings.to_string(b)
}

// record_name_table maps each record index to the brolang identifier it is
// emitted under: its C tag name, or — for an anonymous record named only by a
// typedef — that typedef's name (the typedef is then skipped). Truly anonymous
// records fall back to the loader's synthetic `__c_record_N`.
record_name_table :: proc(result: ^cimport.Result, allocator: mem.Allocator) -> []string {
	names := make([]string, len(result.records), allocator)
	for record, idx in result.records {
		if len(record.name) > 0 {
			names[idx] = record.name
		} else {
			names[idx] = fmt.aprintf("__c_record_%d", idx, allocator=allocator)
		}
	}
	for alias in result.aliases {
		if len(alias.reason) > 0 {
			continue
		}
		ti := alias.type
		if int(ti) < 0 || int(ti) >= len(result.types) {
			continue
		}
		target := result.types[ti]
		if target.kind != .Record || int(target.record) >= len(result.records) {
			continue
		}
		if len(result.records[target.record].name) == 0 {
			names[target.record] = alias.name
		}
	}
	return names
}

// render_type writes the brolang spelling of a C type. Mirror of
// loader.translate_c_type — keep the two in lockstep.
render_type :: proc(b: ^strings.Builder, result: ^cimport.Result, id: cimport.Type_Id, record_names: []string) {
	if id == cimport.INVALID_TYPE || int(id) < 0 || int(id) >= len(result.types) {
		strings.write_string(b, "void")
		return
	}
	item := result.types[id]
	switch item.kind {
	case .Invalid:      strings.write_string(b, "void")
	case .Void:         strings.write_string(b, "void")
	case .C_Char:       strings.write_string(b, "c_char")
	case .C_Schar:      strings.write_string(b, "c_schar")
	case .C_Uchar:      strings.write_string(b, "c_uchar")
	case .C_Short:      strings.write_string(b, "c_short")
	case .C_Ushort:     strings.write_string(b, "c_ushort")
	case .C_Int:        strings.write_string(b, "c_int")
	case .C_Uint:       strings.write_string(b, "c_uint")
	case .C_Long:       strings.write_string(b, "c_long")
	case .C_Ulong:      strings.write_string(b, "c_ulong")
	case .C_Longlong:   strings.write_string(b, "c_longlong")
	case .C_Ulonglong:  strings.write_string(b, "c_ulonglong")
	case .C_Float:      strings.write_string(b, "c_float")
	case .C_Double:     strings.write_string(b, "c_double")
	case .C_Longdouble: strings.write_string(b, "c_longdouble")
	case .Pointer:
		// loader: optional(pointer(child, mutable, many=true)). A Function child
		// yields the `?*c_func(...) T` callback spelling for free.
		strings.write_string(b, "?*")
		if item.mutable {
			strings.write_string(b, "mut ")
		}
		render_type(b, result, item.child, record_names)
	case .Array:
		fmt.sbprintf(b, "[%d]", item.count)
		render_type(b, result, item.child, record_names)
	case .Function:
		render_c_func(b, result, item.params, item.child, item.variadic, record_names)
	case .Record:
		if int(item.record) >= 0 && int(item.record) < len(record_names) {
			strings.write_string(b, record_names[item.record])
		} else {
			strings.write_string(b, "void")
		}
	}
}

// render_c_func writes `c_func(arg0 T0, ...) R`. Params are named arg0.. because
// the parser requires parameter names; names do not affect type identity.
render_c_func :: proc(
	b: ^strings.Builder,
	result: ^cimport.Result,
	params: []cimport.Type_Id,
	ret: cimport.Type_Id,
	variadic: bool,
	record_names: []string,
) {
	strings.write_string(b, "c_func(")
	for param, index in params {
		if index > 0 {
			strings.write_string(b, ", ")
		}
		fmt.sbprintf(b, "arg%d ", index)
		render_type(b, result, param, record_names)
	}
	if variadic {
		if len(params) > 0 {
			strings.write_string(b, ", ")
		}
		strings.write_string(b, "...")
	}
	strings.write_string(b, ") ")
	render_type(b, result, ret, record_names)
}

emit_records :: proc(b: ^strings.Builder, result: ^cimport.Result, record_names: []string) {
	wrote := false
	for record, idx in result.records {
		name := record_names[idx]
		if record.kind == .Union {
			fmt.sbprintf(b, "# unsupported in bindings: C union '%s' has no native spelling\n", name)
			wrote = true
			continue
		}
		if !record.complete || len(record.reason) > 0 {
			// opaque / pointer-only struct
			fmt.sbprintf(b, "%s :: c_struct\n", name)
			wrote = true
			continue
		}
		fmt.sbprintf(b, "%s :: c_struct {{\n", name)
		for field in record.fields {
			fmt.sbprintf(b, "\t%s ", field.name)
			render_type(b, result, field.type, record_names)
			strings.write_byte(b, '\n')
		}
		strings.write_string(b, "}\n")
		wrote = true
	}
	if wrote {
		strings.write_byte(b, '\n')
	}
}

emit_aliases :: proc(b: ^strings.Builder, result: ^cimport.Result, record_names: []string) {
	wrote := false
	for alias in result.aliases {
		if len(alias.reason) > 0 {
			fmt.sbprintf(b, "# unsupported in bindings: typedef '%s' — %s\n", alias.name, alias.reason)
			wrote = true
			continue
		}
		// Skip a typedef that merely (re)names a record under the name we already
		// emitted the record with (anonymous-struct collapse, or `typedef struct
		// Foo Foo;`).
		if ti := alias.type; int(ti) >= 0 && int(ti) < len(result.types) {
			target := result.types[ti]
			if target.kind == .Record && int(target.record) < len(record_names) &&
			   record_names[target.record] == alias.name {
				continue
			}
		}
		fmt.sbprintf(b, "%s :: alias ", alias.name)
		render_type(b, result, alias.type, record_names)
		strings.write_byte(b, '\n')
		wrote = true
	}
	if wrote {
		strings.write_byte(b, '\n')
	}
}

emit_macros :: proc(b: ^strings.Builder, result: ^cimport.Result, record_names: []string) {
	wrote := false
	for macro in result.macros {
		if len(macro.reason) > 0 {
			fmt.sbprintf(b, "# unsupported in bindings: macro '%s' — %s\n", macro.name, macro.reason)
			wrote = true
			continue
		}
		if macro.aggregate {
			emit_aggregate_macro(b, result, macro, record_names)
			wrote = true
			continue
		}
		strings.write_string(b, macro.name)
		if macro_scalar_kind(result, macro.type) {
			strings.write_byte(b, ' ')
			render_type(b, result, macro.type, record_names)
		}
		strings.write_string(b, " :: ")
		render_macro_value(b, macro.value)
		strings.write_byte(b, '\n')
		wrote = true
	}
	if wrote {
		strings.write_byte(b, '\n')
	}
}

emit_aggregate_macro :: proc(
	b: ^strings.Builder,
	result: ^cimport.Result,
	macro: cimport.Macro_Constant,
	record_names: []string,
) {
	ti := macro.type
	if int(ti) >= 0 && int(ti) < len(result.types) && result.types[ti].kind == .Record {
		ridx := int(result.types[ti].record)
		if ridx < len(result.records) {
			record := result.records[ridx]
			if len(record.fields) == len(macro.values) && !record_has_pointer_field(result, record) {
				fmt.sbprintf(b, "%s :: %s {{", macro.name, record_names[ridx])
				for field, index in record.fields {
					if index > 0 {
						strings.write_byte(b, ',')
					}
					fmt.sbprintf(b, " %s = ", field.name)
					render_macro_value(b, macro.values[index])
				}
				strings.write_string(b, " }\n")
				return
			}
		}
	}
	fmt.sbprintf(b, "# unsupported in bindings: aggregate macro '%s' has no native spelling\n", macro.name)
}

emit_functions :: proc(b: ^strings.Builder, result: ^cimport.Result, record_names: []string) {
	wrote := false
	for function in result.functions {
		if len(function.reason) > 0 {
			fmt.sbprintf(b, "# unsupported in bindings: function '%s' — %s\n", function.name, function.reason)
			wrote = true
			continue
		}
		if len(function.link_name) > 0 && function.link_name != function.name {
			fmt.sbprintf(b, "# unsupported in bindings: function '%s' is a static inline function (needs trampoline)\n", function.name)
			wrote = true
			continue
		}
		fmt.sbprintf(b, "%s :: ", function.name)
		render_c_func(b, result, function.params, function.result, function.variadic, record_names)
		strings.write_byte(b, '\n')
		wrote = true
	}
	if wrote {
		strings.write_byte(b, '\n')
	}
}

emit_variables :: proc(b: ^strings.Builder, result: ^cimport.Result) {
	for variable in result.variables {
		fmt.sbprintf(b, "# unsupported in bindings: external variable '%s' has no native spelling\n", variable.name)
	}
}

emit_unsupported :: proc(b: ^strings.Builder, result: ^cimport.Result) {
	for item in result.unsupported {
		fmt.sbprintf(b, "# unsupported in bindings: %s — %s\n", item.name, item.reason)
	}
}

render_macro_value :: proc(b: ^strings.Builder, value: cimport.Macro_Value) {
	switch value.kind {
	case .Integer:
		if value.negative {
			fmt.sbprintf(b, "-%d", value.integer)
		} else {
			fmt.sbprintf(b, "%d", value.integer)
		}
	case .Float:
		number := transmute(f64)value.integer
		text := fmt.tprintf("%v", number)
		strings.write_string(b, text)
		// Ensure it lexes as a float literal, not an integer.
		if strings.index_byte(text, '.') < 0 &&
		   strings.index_byte(text, 'e') < 0 &&
		   strings.index_byte(text, 'E') < 0 {
			strings.write_string(b, ".0")
		}
	case .Invalid:
		strings.write_string(b, "0")
	}
}

macro_scalar_kind :: proc(result: ^cimport.Result, id: cimport.Type_Id) -> bool {
	if int(id) < 0 || int(id) >= len(result.types) {
		return false
	}
	#partial switch result.types[id].kind {
	case .C_Char, .C_Schar, .C_Uchar, .C_Short, .C_Ushort, .C_Int, .C_Uint,
	     .C_Long, .C_Ulong, .C_Longlong, .C_Ulonglong, .C_Float, .C_Double, .C_Longdouble:
		return true
	}
	return false
}

record_has_pointer_field :: proc(result: ^cimport.Result, record: cimport.Record) -> bool {
	for field in record.fields {
		if int(field.type) >= 0 && int(field.type) < len(result.types) &&
		   result.types[field.type].kind == .Pointer {
			return true
		}
	}
	return false
}