// Copyright Epic Games, Inc. All Rights Reserved.

#pragma once

#include <zencore/compactbinary.h>
#include <zencore/string.h>

#include <string_view>

namespace zen {

/// Render a UE structured-log template (as produced by UE_LOGFMT) against a
/// fields bag, writing the result into a caller-provided builder. Grammar:
///
///   format      := (text | escape | placeholder)*
///   escape      := '{{' | '}}'                      (non-localized, default)
///                | '`{' | '`}' | '``'               (localized, $locformat)
///   placeholder := '{' field_path '}'
///   field_path  := name ('.' name | '[' digits ']')*
///   name        := [A-Za-z0-9] [A-Za-z0-9_]*        (leading '_' reserved)
///
/// There are NO inline format specs — `{Name:spec}` is not part of the
/// grammar. Formatting control lives on the value side via nested
/// objects carrying `$text` / `$format` / `$locformat` (see the value-
/// rendering rules in logtemplate.cpp).
///
/// Missing paths render as empty (UE asserts these at emit time, so in
/// practice they don't occur; the empty-render is defensive). Unknown
/// primitive CbField types render as empty.
///
/// Typical use: pass an `ExtendableStringBuilder<256>` so typical messages
/// render on the stack with no heap allocation. The builder is appended to,
/// not cleared, so callers can compose multiple writes if they want.
///
/// @param Template   The format string.
/// @param Fields     The top-level fields bag referenced by placeholders.
/// @param Out        Builder to append the rendered text to.
/// @param Localized  True for $locformat templates (backtick escapes);
///                   false (default) for the top-level `format` field.
void RenderLogTemplate(std::string_view Template, CbObjectView Fields, StringBuilderBase& Out, bool Localized = false);

}  // namespace zen