from __future__ import annotations

import json

import pytest

from scripts.migrate_state_root import (
    STAGING_NAME,
    StateRootMigrationError,
    build_manifest,
    migrate_state_root,
)


def seed_legacy_state(root):
    (root / "templates" / "records").mkdir(parents=True)
    (root / "templates" / "thumbnails").mkdir(parents=True)
    (root / "future-user-data").mkdir()
    (root / "runtime").mkdir()
    (root / ".portrait.tmp").mkdir()
    (root / "config.json").write_text(
        json.dumps({"brightness": 37, "voltage_calibration_factor": 1.01}),
        encoding="utf-8",
    )
    (root / "templates" / "records" / "template.json").write_text("{}", encoding="utf-8")
    (root / "templates" / "thumbnails" / "template.png").write_bytes(b"png")
    (root / "future-user-data" / "keep.bin").write_bytes(b"keep")
    (root / "last_frame.png").write_bytes(b"runtime")
    (root / "startup_indicator.json").write_text("{}", encoding="utf-8")
    (root / "runtime" / "last_frame.png").write_bytes(b"new-runtime")
    (root / ".portrait.tmp" / "keep.bin").write_bytes(b"keep")
    (root / "config.json.tmp").write_text("partial", encoding="utf-8")
    (root / "templates" / "records" / ".record.json.0123456789abcdef0123456789abcdef.tmp").write_text(
        "partial",
        encoding="utf-8",
    )


def test_migration_preserves_persistent_unknown_files_and_keeps_source(tmp_path):
    source = tmp_path / "opt" / "data"
    target = tmp_path / "var" / "lib" / "matrix-screen-controller"
    seed_legacy_state(source)

    result = migrate_state_root(source, target)

    assert result.status == "migrated"
    assert source.is_dir()
    assert (source / "last_frame.png").exists()
    assert (target / "config.json").exists()
    assert (target / "templates" / "records" / "template.json").exists()
    assert (target / "future-user-data" / "keep.bin").read_bytes() == b"keep"
    assert not (target / "last_frame.png").exists()
    assert not (target / "startup_indicator.json").exists()
    assert not (target / "runtime").exists()
    assert (target / ".portrait.tmp" / "keep.bin").read_bytes() == b"keep"
    assert not (target / "config.json.tmp").exists()
    assert not (
        target
        / "templates"
        / "records"
        / ".record.json.0123456789abcdef0123456789abcdef.tmp"
    ).exists()
    assert build_manifest(source) == build_manifest(target)


def test_migration_is_idempotent_when_target_matches(tmp_path):
    source = tmp_path / "legacy"
    target = tmp_path / "state"
    seed_legacy_state(source)
    migrate_state_root(source, target)

    second = migrate_state_root(source, target)

    assert second.status == "already-prepared"
    assert not (target.parent / STAGING_NAME).exists()


def test_migration_refuses_different_nonempty_target_without_modifying_it(tmp_path):
    source = tmp_path / "legacy"
    target = tmp_path / "state"
    seed_legacy_state(source)
    target.mkdir()
    existing = target / "config.json"
    existing.write_text('{"brightness": 99}', encoding="utf-8")
    before = existing.read_bytes()

    with pytest.raises(StateRootMigrationError, match="refusing to merge"):
        migrate_state_root(source, target)

    assert existing.read_bytes() == before
    assert not (target.parent / STAGING_NAME).exists()


def test_missing_source_keeps_current_target_untouched(tmp_path):
    source = tmp_path / "missing"
    target = tmp_path / "state"
    target.mkdir()
    config = target / "config.json"
    config.write_text('{"schema_version": 1}', encoding="utf-8")

    result = migrate_state_root(source, target)

    assert result.status == "target-only"
    assert config.read_text(encoding="utf-8") == '{"schema_version": 1}'


def test_migration_refuses_overlapping_state_roots(tmp_path):
    source = tmp_path / "legacy"
    seed_legacy_state(source)

    with pytest.raises(StateRootMigrationError, match="must not contain"):
        migrate_state_root(source, source / "new-state")


def test_missing_source_and_empty_target_fail_closed(tmp_path):
    source = tmp_path / "missing"
    target = tmp_path / "empty"
    target.mkdir()

    with pytest.raises(StateRootMigrationError, match="no persistent files"):
        migrate_state_root(source, target)


def test_empty_legacy_source_fails_closed(tmp_path):
    source = tmp_path / "empty-source"
    source.mkdir()

    with pytest.raises(StateRootMigrationError, match="source contains no persistent files"):
        migrate_state_root(source, tmp_path / "target")


def test_state_root_symlink_is_rejected(tmp_path):
    real_source = tmp_path / "real-source"
    seed_legacy_state(real_source)
    source_link = tmp_path / "source-link"
    try:
        source_link.symlink_to(real_source, target_is_directory=True)
    except OSError:
        pytest.skip("directory symlinks are unavailable on this host")

    with pytest.raises(StateRootMigrationError, match="must not be symlinks"):
        migrate_state_root(source_link, tmp_path / "target")