// SPDX-License-Identifier: GPL-3.0-only
// Pure, hardware-independent HTTP Range header parser. Header-only so it compiles both on
// the ESP32 and on the host for native unit tests (see firmware/test, docs/testing.md).
#pragma once

#include <stddef.h>

namespace oshttp {

struct RangeResult {
  bool partial;       // a "bytes=" range was requested
  bool satisfiable;   // start is within the file
  size_t start;       // inclusive
  size_t end;         // inclusive
};

// Parse a Range header value like "bytes=START-END" (END optional) against a known total
// size. If header is null/empty or not a bytes range, returns partial=false (send full
// body). A start past the end sets satisfiable=false (caller sends 416).
inline RangeResult parseByteRange(const char *header, size_t total) {
  RangeResult r{false, true, 0, total ? total - 1 : 0};
  if (!header) return r;

  const char *prefix = "bytes=";
  for (size_t i = 0; prefix[i]; ++i) {
    if (header[i] != prefix[i]) return r;  // not a bytes range -> full body
  }
  r.partial = true;

  const char *s = header + 6;
  size_t start = 0;
  while (*s >= '0' && *s <= '9') { start = start * 10 + (*s - '0'); ++s; }
  if (*s != '-') { r.partial = false; return r; }  // malformed -> full body
  ++s;

  size_t end = total ? total - 1 : 0;
  bool anyEnd = false;
  size_t ev = 0;
  while (*s >= '0' && *s <= '9') { ev = ev * 10 + (*s - '0'); ++s; anyEnd = true; }
  if (anyEnd) end = ev;

  if (start >= total) { r.satisfiable = false; r.start = start; r.end = end; return r; }
  if (end >= total) end = total ? total - 1 : 0;
  r.start = start;
  r.end = end;
  return r;
}

}  // namespace oshttp