#!/usr/bin/env python3
"""Validate toolchain pins and Go 1.20 compatibility of core/win7 modules."""

import json
import os
import pathlib
import re
import subprocess
import sys


MAX_LEGACY_GO_VERSION = (1, 20)


def version_tuple(value):
    match = re.fullmatch(r"(\d+)\.(\d+)(?:\.(\d+))?", value)
    if not match:
        raise ValueError("invalid Go version {!r}".format(value))
    return tuple(int(part or 0) for part in match.groups())


def decode_json_stream(text):
    decoder = json.JSONDecoder()
    index = 0
    while index < len(text):
        while index < len(text) and text[index].isspace():
            index += 1
        if index >= len(text):
            return
        value, index = decoder.raw_decode(text, index)
        yield value


def read_text(path):
    return path.read_text(encoding="utf-8")


def go_directive(path):
    match = re.search(r"(?m)^go\s+(\d+\.\d+(?:\.\d+)?)\s*$", read_text(path))
    if not match:
        raise ValueError("{} has no go directive".format(path))
    return match.group(1)


def required_version(path, module_path):
    pattern = r"(?m)^\s*{}\s+(v[^\s]+)".format(re.escape(module_path))
    match = re.search(pattern, read_text(path))
    if not match:
        raise ValueError(
            "{} does not require {}".format(path, module_path)
        )
    return match.group(1)


def run_go(repo_root, cwd, arguments, go_work):
    environment = os.environ.copy()
    environment["GOWORK"] = str(go_work) if go_work else "off"
    result = subprocess.run(
        ["go"] + arguments,
        cwd=str(cwd),
        env=environment,
        check=False,
        stdout=subprocess.PIPE,
        stderr=subprocess.PIPE,
        universal_newlines=True,
    )
    if result.returncode != 0:
        print(result.stderr, file=sys.stderr, end="")
        raise SystemExit(result.returncode)
    return result.stdout


def validate_pins(repo_root):
    expected_go_directives = {
        repo_root / "go.work": "1.25.0",
        repo_root / "core" / "go.mod": "1.20",
        repo_root / "app-modern" / "go.mod": "1.25.0",
        repo_root / "app-win7" / "go.mod": "1.20",
        repo_root / "app-win7" / "go.work": "1.20",
    }
    violations = []

    for path, expected in expected_go_directives.items():
        actual = go_directive(path)
        if actual != expected:
            violations.append(
                "{} go directive is {}, want {}".format(
                    path.relative_to(repo_root), actual, expected
                )
            )

    gio_pins = {
        repo_root / "app-modern" / "go.mod": "v0.10.1",
        repo_root / "app-win7" / "go.mod": "v0.6.0",
    }
    for path, expected in gio_pins.items():
        actual = required_version(path, "gioui.org")
        if actual != expected:
            violations.append(
                "{} pins gioui.org {}, want {}".format(
                    path.relative_to(repo_root), actual, expected
                )
            )

    return violations


def validate_go20_toolchain(repo_root):
    output = run_go(repo_root, repo_root, ["version"], None).strip()
    if "go1.20.14" not in output:
        return ["compatibility scan uses {!r}, want go1.20.14".format(output)]
    return []


def validate_module_versions(repo_root):
    module_sets = (
        ("core", repo_root / "core", None),
        (
            "win7",
            repo_root / "app-win7",
            repo_root / "app-win7" / "go.work",
        ),
    )
    violations = []
    checked = 0

    for label, cwd, go_work in module_sets:
        output = run_go(
            repo_root,
            cwd,
            ["list", "-m", "-json", "all"],
            go_work,
        )
        for module in decode_json_stream(output):
            checked += 1
            go_version = module.get("GoVersion")
            if not go_version:
                continue
            if version_tuple(go_version)[:2] > MAX_LEGACY_GO_VERSION:
                violations.append(
                    "{} module {} declares go {}, exceeds 1.20".format(
                        label, module["Path"], go_version
                    )
                )

    return violations, checked


def self_check():
    if version_tuple("1.20")[:2] > MAX_LEGACY_GO_VERSION:
        raise AssertionError("Go 1.20 should be accepted")
    if version_tuple("1.20.14")[:2] > MAX_LEGACY_GO_VERSION:
        raise AssertionError("Go 1.20.14 should be accepted")
    if not version_tuple("1.21")[:2] > MAX_LEGACY_GO_VERSION:
        raise AssertionError("Go 1.21 should be rejected")


def main():
    self_check()
    repo_root = pathlib.Path(__file__).resolve().parents[1]
    violations = validate_pins(repo_root)
    violations.extend(validate_go20_toolchain(repo_root))
    module_violations, checked = validate_module_versions(repo_root)
    violations.extend(module_violations)

    if violations:
        for violation in violations:
            print("ERROR: " + violation, file=sys.stderr)
        raise SystemExit(1)

    print(
        "Go version check passed: pins valid; {} module records are Go 1.20-compatible.".format(
            checked
        )
    )


if __name__ == "__main__":
    main()