"""Migration 008's data rewrite: realign already-materialised flexible series.

`project_window` (`app/entities/leave_wish.py`) now snaps a `window_mode ==
'flexible'` bound's start to the anchor year's start weekday too (Step 1 of
the flexible-window realignment fix), holding the bound's day-span fixed —
mirroring what `window_mode == 'fixed'` already did. But `project_window`
only runs once, at materialisation time (`LeaveWishService`); nothing
re-derives it at read time. Every flexible series row materialised before
this fix therefore stays unsnapped forever unless something rewrites it
once. Migration 008 is that one-time rewrite.

Driven through the real Alembic chain (upgrade to 007, insert POST-004-shape
rows directly — the one-row-per-year shape already exists by 007, so there is
no pre-004 fixture to build here — then upgrade to head/008), mirroring
`test_migration_004_backfill.py`'s style.
"""

from __future__ import annotations

import sqlite3
import uuid
from datetime import date, datetime
from pathlib import Path
from typing import Any

from alembic import command
from alembic.config import Config


def _alembic_config(db_path: Path) -> Config:
    cfg = Config("alembic.ini")
    cfg.set_main_option("sqlalchemy.url", f"sqlite:///{db_path}")
    return cfg


def _insert_post_004_fixture(db_path: Path, *, rows: list[dict[str, object]]) -> str:
    """Seed a workspace and the given POST-004-shape `leave_wish` rows.

    `rows` are full leave_wish rows (one per year already) — the shape 004
    produces and 007 leaves untouched — grouped by `series_id`.
    """
    now = datetime(2026, 1, 1, 12, 0, 0).isoformat()
    ws_id = str(uuid.uuid4())

    conn = sqlite3.connect(db_path)
    try:
        conn.execute(
            "INSERT INTO workspace (id, name, created_at) VALUES (?, ?, ?)",
            (ws_id, "WS", now),
        )
        for row in rows:
            conn.execute(
                "INSERT INTO leave_wish (id, workspace_id, child_id, name, "
                "window_start_month, window_start_day, window_end_month, window_end_day, "
                "target_weeks, first_year, last_year, priority, parent_mode, "
                "window_mode, series_id, created_at, updated_at) "
                "VALUES (:id, :workspace_id, NULL, :name, :wsm, :wsd, :wem, :wed, "
                ":target_weeks, :first_year, :last_year, 1, 'either', "
                ":window_mode, :series_id, :now, :now)",
                {"workspace_id": ws_id, "now": now, **row},
            )
        conn.commit()
    finally:
        conn.close()
    return ws_id


def _rows(db_path: Path, name: str) -> list[sqlite3.Row]:
    conn = sqlite3.connect(db_path)
    conn.row_factory = sqlite3.Row
    try:
        return conn.execute(
            "SELECT * FROM leave_wish WHERE name = ? ORDER BY first_year", (name,)
        ).fetchall()
    finally:
        conn.close()


def _flexible_series(
    *, name: str, series_id: str, first_year: int, last_year: int, wsm: int, wsd: int
) -> list[dict[str, Any]]:
    """Rows in 004's shape for a flexible series whose bound was NAIVELY

    materialised (every year the identical month/day pair) — exactly what
    every flexible series looked like before this fix, and what 008 must
    rewrite.
    """
    return [
        {
            "id": str(uuid.uuid4()),
            "name": name,
            "wsm": wsm,
            "wsd": wsd,
            "wem": 5,
            "wed": 31,
            "target_weeks": 1,
            "first_year": year,
            "last_year": last_year,
            "window_mode": "flexible",
            "series_id": series_id,
        }
        for year in range(first_year, last_year + 1)
    ]


def test_upgrade_realigns_a_flexible_series_onto_its_anchor_weekday(tmp_path: Path) -> None:
    db = tmp_path / "realign.db"
    command.upgrade(_alembic_config(db), "007")

    series_id = str(uuid.uuid4())
    # 2027-03-01 is a Monday; naively every year got the same (3, 1).
    rows_in = _flexible_series(
        name="Var", series_id=series_id, first_year=2027, last_year=2029, wsm=3, wsd=1
    )
    _insert_post_004_fixture(db, rows=rows_in)

    command.upgrade(_alembic_config(db), "head")

    rows = _rows(db, "Var")
    assert [r["first_year"] for r in rows] == [2027, 2028, 2029]
    # Anchor (2027) untouched; 2028/2029 snapped to Monday, span held fixed.
    stored = [(r["window_start_month"], r["window_start_day"]) for r in rows]
    assert stored == [(3, 1), (2, 28), (2, 26)]
    for row in rows:
        start = date(row["first_year"], row["window_start_month"], row["window_start_day"])
        end = date(row["first_year"], row["window_end_month"], row["window_end_day"])
        assert start.weekday() == 0, row["first_year"]
        assert (end - start).days == 91, row["first_year"]


def test_downgrade_restores_the_naive_anchor_month_day(tmp_path: Path) -> None:
    db = tmp_path / "realign_roundtrip.db"
    command.upgrade(_alembic_config(db), "007")

    series_id = str(uuid.uuid4())
    rows_in = _flexible_series(
        name="Var", series_id=series_id, first_year=2027, last_year=2029, wsm=3, wsd=1
    )
    _insert_post_004_fixture(db, rows=rows_in)

    command.upgrade(_alembic_config(db), "head")
    assert {(r["window_start_month"], r["window_start_day"]) for r in _rows(db, "Var")} != {(3, 1)}

    command.downgrade(_alembic_config(db), "007")

    rows = _rows(db, "Var")
    assert [r["first_year"] for r in rows] == [2027, 2028, 2029]
    assert {(r["window_start_month"], r["window_start_day"]) for r in rows} == {(3, 1)}
    assert {(r["window_end_month"], r["window_end_day"]) for r in rows} == {(5, 31)}


def test_fixed_series_is_left_untouched(tmp_path: Path) -> None:
    """`project_window` already snapped a fixed series correctly at 004's

    materialisation time — 008 must be a no-op for it, not a costly
    re-run of an already-correct projection.
    """
    db = tmp_path / "fixed_untouched.db"
    command.upgrade(_alembic_config(db), "007")

    series_id = str(uuid.uuid4())
    rows_in = [
        {
            "id": str(uuid.uuid4()),
            "name": "Sommar",
            "wsm": 10,
            "wsd": 5 if year == 2026 else (4 if year == 2027 else 2),
            "wem": 10,
            "wed": 11 if year == 2026 else (10 if year == 2027 else 8),
            "target_weeks": 1,
            "first_year": year,
            "last_year": 2028,
            "window_mode": "fixed",
            "series_id": series_id,
        }
        for year in (2026, 2027, 2028)
    ]
    _insert_post_004_fixture(db, rows=rows_in)

    before = {r["first_year"]: dict(r) for r in _rows(db, "Sommar")}
    command.upgrade(_alembic_config(db), "head")
    after = {r["first_year"]: dict(r) for r in _rows(db, "Sommar")}

    for year, row in before.items():
        assert after[year]["window_start_month"] == row["window_start_month"]
        assert after[year]["window_start_day"] == row["window_start_day"]
        assert after[year]["window_end_month"] == row["window_end_month"]
        assert after[year]["window_end_day"] == row["window_end_day"]