#+private
#+build windows
package debug_trace

import "base:intrinsics"
import "base:runtime"

import win32 "core:sys/windows"
import "core:fmt"

_Context :: struct {
	hProcess: win32.HANDLE,
	lock:     win32.SRWLOCK,
}

_init :: proc "contextless" (ctx: ^Context) -> (ok: bool) {
	defer if !ok { _destroy(ctx) }
	ctx.impl.hProcess = win32.GetCurrentProcess()
	win32.SymInitialize(ctx.impl.hProcess, nil, true) or_return
	win32.SymSetOptions(win32.SYMOPT_LOAD_LINES)
	return true
}

_destroy :: proc "contextless" (ctx: ^Context) -> bool {
	if ctx != nil {
		win32.SymCleanup(ctx.impl.hProcess)
	}
	return true
}

_frames :: proc "contextless" (ctx: ^Context, skip: uint, frames_buffer: []Frame) -> []Frame {
	frame_count := win32.RtlCaptureStackBackTrace(u32(skip) + 2, u32(len(frames_buffer)), ([^]rawptr)(&frames_buffer[0]), nil)
	for i in 0..<frame_count {
		// NOTE: Return address is one after the call instruction so subtract a byte to
		// end up back inside the call instruction which is needed for SymFromAddr.
		frames_buffer[i] -= 1
	}
	return frames_buffer[:frame_count]
}


_resolve :: proc(ctx: ^Context, frame: Frame, allocator: runtime.Allocator) -> (fl: Frame_Location) {
	intrinsics.atomic_store(&ctx.in_resolve, true)
	defer intrinsics.atomic_store(&ctx.in_resolve, false)

	// NOTE(bill): Dbghelp is not thread-safe
	win32.AcquireSRWLockExclusive(&ctx.impl.lock)
	defer win32.ReleaseSRWLockExclusive(&ctx.impl.lock)

	data: [size_of(win32.SYMBOL_INFOW) + size_of([256]win32.WCHAR)]byte
	symbol := (^win32.SYMBOL_INFOW)(&data[0])
	// The value of SizeOfStruct must be the size of the whole struct,
	// not just the size of the pointer
	symbol.SizeOfStruct = size_of(symbol^)
	symbol.MaxNameLen = 255
	if win32.SymFromAddrW(ctx.impl.hProcess, win32.DWORD64(frame), &{}, symbol) {
		fl.procedure, _ = win32.wstring_to_utf8(cstring16(&symbol.Name[0]), -1, allocator)
	} else {
		fl.procedure = fmt.aprintf("(procedure: 0x%x)", frame, allocator=allocator)
	}

	line: win32.IMAGEHLP_LINE64
	line.SizeOfStruct = size_of(line)
	if win32.SymGetLineFromAddrW64(ctx.impl.hProcess, win32.DWORD64(frame), &{}, &line) {
		fl.file_path, _ = win32.wstring_to_utf8(line.FileName, -1, allocator)
		fl.line = i32(line.LineNumber)
	}

	return
}