#!/usr/bin/env python3
import os
import sys
import subprocess
from pathlib import Path
import shutil

# ---------------------------------------------------------------------
# CONFIG
# ---------------------------------------------------------------------
SRC_DIR = Path("src")
TEST_DIR = Path("tests")
OBJ_DIR = Path("obj")
BIN_DIR = Path("bin")

TARGET = BIN_DIR / "sls"
TEST_TARGET = BIN_DIR / "sls_tests"

# Unix gcc/clang flags
COMMON_FLAGS = ["-std=c99", "-Wall", "-Wextra", "-Werror", "-Iinclude", "-g"]
TEST_FLAGS = ["-std=c99", "-Wall", "-Wextra", "-Wno-unused-function", "-Werror",
              "-Iinclude", "-g", "-O0"]

# Windows MSVC flags
MSVC_FLAGS = ["/std:c11", "/Zi", "/Iinclude"]
MSVC_TEST_FLAGS = MSVC_FLAGS + []

# ---------------------------------------------------------------------
# COMPILER DETECTION
# ---------------------------------------------------------------------
def detect_compiler():
    if os.name == "nt":
        return ("cl", "msvc")
    return ("gcc", "gcc")

CC, CC_KIND = detect_compiler()

# ---------------------------------------------------------------------
# PYTHON DETECTION
# ---------------------------------------------------------------------
def detect_python():
    if os.name == "nt":
        return "python"
    return "python3"

PYTHON = detect_python()


# ---------------------------------------------------------------------
# GIT COMMIT HASH
# ---------------------------------------------------------------------
def git_commit_hash():
    try:
        result_hash = subprocess.check_output(
            ["git", "describe", "--always", "--dirty", "--abbrev=7"],
            cwd=".",
            stderr=subprocess.DEVNULL,
            text=True
        ).strip()
        result_date = subprocess.check_output(
            ["git", "show", "-s", "--format=%ci"],
            cwd=".",
            stderr=subprocess.DEVNULL,
            text=True
        ).strip()
        return f"{result_hash} {result_date}"
    except Exception:
        return "unknown"


GIT_HASH = git_commit_hash()


# ---------------------------------------------------------------------
# UTILS
# ---------------------------------------------------------------------
def mkdir(p: Path):
    p.mkdir(parents=True, exist_ok=True)


def run(cmd):
    print(">>", " ".join(cmd))
    subprocess.check_call(cmd)


def is_up_to_date(src, obj, dep):
    if "meta" in [src.stem, obj.stem, dep.stem]:
        return False
    if not obj.exists():
        return False
    if dep.exists() and dep.stat().st_mtime > obj.stat().st_mtime:
        return False
    return src.stat().st_mtime < obj.stat().st_mtime


# ---------------------------------------------------------------------
# BUILD RULES
# ---------------------------------------------------------------------
def compile_source(src: Path, is_test=False):
    mkdir(OBJ_DIR)
    obj = OBJ_DIR / (src.stem + ".o")
    dep = OBJ_DIR / (src.stem + ".d")

    if is_up_to_date(src, obj, dep):
        return obj

    if CC_KIND == "msvc":
        flags = MSVC_TEST_FLAGS if is_test else MSVC_FLAGS
        cmd = [CC] + flags + ["/Fo" + str(obj), "/c", str(src),
                               f"/DGIT_COMMIT_HASH=\"{GIT_HASH}\""]
    else:
        flags = TEST_FLAGS if is_test else COMMON_FLAGS
        cmd = [CC] + flags + [
            f"-DGIT_COMMIT_HASH=\"{GIT_HASH}\"",
            "-MMD", "-MP",
            "-c", str(src), "-o", str(obj)
        ]

    run(cmd)
    return obj


def link_executable(objects, output: Path):
    mkdir(BIN_DIR)
    if CC_KIND == "msvc":
        cmd = [CC] + list(map(str, objects)) + ["/Fe" + str(output)]
    else:
        cmd = [CC] + list(map(str, objects)) + ["-lm", "-o", str(output)]
    run(cmd)


# ---------------------------------------------------------------------
# TEST CASE GENERATION
# ---------------------------------------------------------------------
def generate_tests():
    script = Path("../SLS_Tests/yaml_to_c_tests.py")
    yaml = Path("../SLS_Tests/cases.yaml")
    out = TEST_DIR / "lexer_tests.c"

    if not script.exists() or not yaml.exists():
        print("Test generation skipped (missing files).")
        return False

    if out.exists() and out.stat().st_mtime > yaml.stat().st_mtime:
        return True

    run([PYTHON, str(script), str(yaml), str(out)])
    return True


# ---------------------------------------------------------------------
# TARGETS
# ---------------------------------------------------------------------
def build_main():
    sources = list(SRC_DIR.glob("*.c"))
    objects = [compile_source(s, is_test=False) for s in sources]
    link_executable(objects, TARGET)


def build_tests():
    generate_tests()
    test_sources = list(TEST_DIR.glob("*.c"))
    main_sources = [s for s in SRC_DIR.glob("*.c") if s.name != "main.c"]

    test_objects = [compile_source(s, is_test=True) for s in test_sources]
    shared_objects = [compile_source(s, is_test=False) for s in main_sources]

    link_executable(test_objects + shared_objects, TEST_TARGET)


def clean():
    shutil.rmtree(OBJ_DIR, ignore_errors=True)
    shutil.rmtree(BIN_DIR, ignore_errors=True)
    print("Cleaned.")


def run_main():
    build_main()
    print("\n--- Running program ---\n")
    subprocess.call([str(TARGET)])


def run_tests():
    build_tests()
    print("\n--- Running tests ---\n")
    subprocess.call([str(TEST_TARGET)])


def debug_tests():
    build_tests()
    if os.name == "nt":
        print("Debugging on Windows requires Visual Studio debugger.")
    else:
        subprocess.call(["gdb", str(TEST_TARGET)])


# ---------------------------------------------------------------------
# ENTRY POINT
# ---------------------------------------------------------------------
def main():
    if len(sys.argv) < 2:
        print("Usage: python3 build.py [all|build|test|run|debug|clean]")
        return

    cmd = sys.argv[1]

    match cmd:
        case "all" | "main":
            build_main()
        case "build":
            build_main()
        case "run":
            run_main()
        case "test":
            run_tests()
        case "debug":
            debug_tests()
        case "clean":
            clean()
        case _:
            print(f"Unknown target: {cmd}")


if __name__ == "__main__":
    main()