"""Program schema — per-program DB table definitions + subprogram list."""

from __future__ import annotations
from dataclasses import dataclass, field
from pathlib import Path
from typing import Optional


@dataclass
class ColumnDef:
    name: str
    type: str           # SQL type: "CHAR(6)", "NUMERIC(4)", "VARCHAR(30)"
    primary_key: bool = False
    nullable: bool = False
    default: Optional[str] = None
    cobol_field: Optional[str] = None   # COBOL field name if different


@dataclass
class TableDef:
    name: str
    columns: list[ColumnDef] = field(default_factory=list)
    create_if_missing: bool = True
    sql_name: Optional[str] = None   # COBOL SQL table name if different from YAML name


@dataclass
class ProgramSchema:
    program_id: str
    db_tables: list[TableDef] = field(default_factory=list)
    subprograms: list[str] = field(default_factory=list)
    db_type: str = "SQLite"
    db_name: str = "OVERTIME.DB"

    @classmethod
    def from_yaml(cls, path: str | Path) -> ProgramSchema:
        import yaml
        with open(path, encoding="utf-8") as f:
            raw = yaml.safe_load(f)
        tables = []
        for t in raw.get("db_tables", []):
            cols = [ColumnDef(**c) for c in t.get("columns", [])]
            tables.append(TableDef(
                name=t["name"], columns=cols,
                sql_name=t.get("sql_name"),
            ))
        return cls(
            program_id=raw["program_id"],
            db_tables=tables,
            subprograms=raw.get("subprograms", []),
            db_type=raw.get("db_type", "SQLite"),
            db_name=raw.get("db_name", "OVERTIME.DB"),
        )


def load_schema(program_id: str, search_dirs: list[str | Path] | None = None) -> ProgramSchema:
    """Load per-program YAML schema by program ID."""
    if search_dirs is None:
        search_dirs = [Path(__file__).parent / "programs"]
    for d in search_dirs:
        p = Path(d) / f"{program_id}.yaml"
        if p.exists():
            return ProgramSchema.from_yaml(p)
    raise FileNotFoundError(f"Schema not found for {program_id} in {search_dirs}")