Livt.Web

src/http/HttpResponseSyntax.lvt

namespace Livt.Web.Http

using Livt.Net

/**
 * Stateless internal wire vocabulary; callers validate metadata first.
 */
component HttpResponseSyntax
{
	// Byte extents shared with the response encoder.
	public const LENGTH_PREFIX_LENGTH: int = 16
	public const END_LENGTH: int = 23

	// Starts of the fixed fragments in the packed wire vocabulary.
	const LENGTH_PREFIX_OFFSET: int = 262
	const END_OFFSET: int = 278

	// Packed HTTP/1.0 status/header literals; descriptor offsets refer to this table.
	const WIRE[301] = [
		0x48, 0x54, 0x54, 0x50, 0x2F, 0x31, 0x2E, 0x30, 0x20, 0x32, 0x30, 0x30, 0x20, 0x4F, 0x4B, 0x0D,
		0x0A, 0x48, 0x54, 0x54, 0x50, 0x2F, 0x31, 0x2E, 0x30, 0x20, 0x34, 0x30, 0x30, 0x20, 0x42, 0x61,
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		0x20, 0x45, 0x72, 0x72, 0x6F, 0x72, 0x0D, 0x0A, 0x43, 0x6F, 0x6E, 0x74, 0x65, 0x6E, 0x74, 0x2D,
		0x54, 0x79, 0x70, 0x65, 0x3A, 0x20, 0x74, 0x65, 0x78, 0x74, 0x2F, 0x68, 0x74, 0x6D, 0x6C, 0x0D,
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		0x6F, 0x6E, 0x3A, 0x20, 0x63, 0x6C, 0x6F, 0x73, 0x65, 0x0D, 0x0A, 0x0D, 0x0A]

	/**
	 * Returns the packed status line start, or -1 for an unsupported/absent value.
	 */
	public static inline fn GetStatusOffset[](value: HttpStatus) int
	{
		match value
		{
			HttpStatus.Ok =>
			{
				return 0
			}

			HttpStatus.BadRequest =>
			{
				return 17
			}

			HttpStatus.NotFound =>
			{
				return 43
			}

			HttpStatus.MethodNotAllowed =>
			{
				return 67
			}

			HttpStatus.InternalServerError =>
			{
				return 100
			}

			_ =>
			{
				return -1
			}
		}
	}

	/**
	 * Returns the status line byte length including CRLF, or zero when absent/unsupported.
	 */
	public static inline fn GetStatusLength[](value: HttpStatus) int
	{
		match value
		{
			HttpStatus.Ok =>
			{
				return 17
			}

			HttpStatus.BadRequest =>
			{
				return 26
			}

			HttpStatus.NotFound =>
			{
				return 24
			}

			HttpStatus.MethodNotAllowed =>
			{
				return 33
			}

			HttpStatus.InternalServerError =>
			{
				return 36
			}

			_ =>
			{
				return 0
			}
		}
	}

	/**
	 * Returns the packed Content-Type header start, or -1 for an unsupported/absent value.
	 */
	public static inline fn GetContentTypeOffset[](value: HttpContentType) int
	{
		match value
		{
			HttpContentType.Html =>
			{
				return 136
			}

			HttpContentType.PlainText =>
			{
				return 161
			}

			HttpContentType.Json =>
			{
				return 187
			}

			_ =>
			{
				return -1
			}
		}
	}

	/**
	 * Returns the Content-Type header byte length including CRLF, or zero when absent/unsupported.
	 */
	public static inline fn GetContentTypeLength[](value: HttpContentType) int
	{
		match value
		{
			HttpContentType.Html =>
			{
				return 25
			}

			HttpContentType.PlainText =>
			{
				return 26
			}

			HttpContentType.Json =>
			{
				return 32
			}

			_ =>
			{
				return 0
			}
		}
	}

	/**
	 * Returns the packed Allow header start, or -1 for an unsupported/absent value.
	 */
	public static inline fn GetAllowedMethodsOffset[](value: HttpAllowedMethods) int
	{
		match value
		{
			HttpAllowedMethods.Get =>
			{
				return 219
			}

			HttpAllowedMethods.Head =>
			{
				return 231
			}

			HttpAllowedMethods.GetAndHead =>
			{
				return 244
			}

			_ =>
			{
				return -1
			}
		}
	}

	/**
	 * Returns the Allow header byte length including CRLF, or zero when absent/unsupported.
	 */
	public static inline fn GetAllowedMethodsLength[](value: HttpAllowedMethods) int
	{
		match value
		{
			HttpAllowedMethods.Get =>
			{
				return 12
			}

			HttpAllowedMethods.Head =>
			{
				return 13
			}

			HttpAllowedMethods.GetAndHead =>
			{
				return 18
			}

			_ =>
			{
				return 0
			}
		}
	}

	/**
	 * Checks status/media support and Allow consistency; only a 405 response
	 * accepts a nonempty supported method set.
	 */
	public static inline fn IsSupported[](status: HttpStatus, contentType: HttpContentType, allowed: HttpAllowedMethods) bool
	{
		if (HttpResponseSyntax.GetStatusLength(status) == 0 || HttpResponseSyntax.GetContentTypeLength(contentType) == 0) {
			return false
		}

		if (status == HttpStatus.MethodNotAllowed) {
			return HttpResponseSyntax.GetAllowedMethodsLength(allowed) > 0
		}

		return allowed == HttpAllowedMethods.None
	}

	/**
	 * Reads the packed wire vocabulary at an already validated absolute byte index.
	 */
	public static inline fn GetByte[](index: int) byte
	{
		return WIRE[index]
	}

	/**
	 * Reads the 16-byte Content-Length prefix; requires index in 0..15.
	 */
	public static inline fn GetLengthPrefixByte[](index: int) byte
	{
		return WIRE[LENGTH_PREFIX_OFFSET + index]
	}

	/**
	 * Reads the 23-byte CRLF/Connection: close/CRLF suffix; requires index in 0..22.
	 */
	public static inline fn GetEndByte[](index: int) byte
	{
		return WIRE[END_OFFSET + index]
	}
}