import os
import shutil
import struct
import subprocess


# Mixed into DevCommand (bin/dev), which provides _project_root.
class ShadersCommand:
    SHADER_EXTENSIONS = (".vert", ".frag", ".comp", ".geom", ".tesc", ".tese")

    def shaders(self, *args, **kwargs):
        shaders_dir = os.path.join(self._project_root(), "engine", "src", "shaders")
        if not os.path.isdir(shaders_dir):
            raise ValueError(f"Shaders directory not found: {shaders_dir}")

        glslc = self._find_glslc()

        shader_paths = sorted(
            os.path.join(root, filename)
            for root, _dirs, files in os.walk(shaders_dir)
            for filename in files
            if filename.endswith(self.SHADER_EXTENSIONS)
        )

        if not shader_paths:
            print(f"No shaders found in {shaders_dir}")
            return

        for shader_path in shader_paths:
            self._generate_shader_header(glslc, shader_path)

    def _find_glslc(self):
        glslc = shutil.which("glslc")
        if glslc is None:
            raise RuntimeError(
                "glslc not found on PATH (install the Vulkan SDK)"
            )
        return glslc

    def _generate_shader_header(self, glslc, shader_path):
        relative_path = os.path.relpath(shader_path, self._project_root())
        print(f"Compiling shader: {relative_path}")

        result = subprocess.run(
            [glslc, shader_path, "-o", "-"],
            stdout=subprocess.PIPE,
            stderr=subprocess.PIPE,
        )
        if result.returncode != 0:
            raise RuntimeError(
                f"failed to compile {shader_path}: {result.stderr.decode()}"
            )

        spirv = result.stdout
        if len(spirv) % 4 != 0:
            raise RuntimeError(
                f"invalid SPIR-V output for {shader_path} (size not a multiple of 4)"
            )

        word_count = len(spirv) // 4
        words = struct.unpack(f"<{word_count}I", spirv)

        filename = os.path.basename(shader_path)
        variable_name = f"{filename.replace('.', '_')}_spv"
        header_path = shader_path + ".spv.h"

        body_lines = [
            "    " + ", ".join(f"0x{word:08x}" for word in words[i:i + 4]) + ","
            for i in range(0, len(words), 4)
        ]

        header = "\n".join([
            "#pragma once",
            "",
            "#include <array>",
            "#include <cstdint>",
            "",
            "namespace sophia::shaders {",
            "",
            f"inline constexpr std::array<uint32_t, {word_count}> {variable_name} = {{",
            *body_lines,
            "};",
            "",
            "}  // namespace sophia::shaders",
            "",
        ])

        with open(header_path, "w") as f:
            f.write(header)

        print(f"Wrote {os.path.relpath(header_path, self._project_root())} "
              f"({word_count * 4} bytes)")