"""Build-target DAG construction.

F-11 remediation: the 6-branch if/elif chain on ``target.system``
has been replaced with a dispatch table (``_SYSTEM_BUILDERS``).
Adding a new build system is now a one-line dict entry instead of
a new elif branch.
"""

from __future__ import annotations

from typing import Any, Callable, Dict, List, Mapping


def build_target_dag(project: Mapping[str, Any], targets: list) -> List[Dict[str, Any]]:
    """Build a DAG of {name, target, steps} for each target in ``targets``."""
    return [
        {
            "name": f"{t.system}-{t.arch}",
            "target": t,
            "steps": generate_steps(project, t),
        }
        for t in targets
    ]


# ---------------------------------------------------------------------------
# Per-system command builders
# ---------------------------------------------------------------------------
def _cmd(name: str, command: str) -> Dict[str, str]:
    """Helper: build a {name, command} step dict."""
    return {"name": name, "command": command}


def _build_gentoo(project: Mapping[str, Any], target: Any) -> List[Dict[str, str]]:
    return [_cmd("emerge", f"emerge -e {project['name']}")]


def _build_buildroot(project: Mapping[str, Any], target: Any) -> List[Dict[str, str]]:
    return [_cmd("buildroot", "make")]


def _build_openwrt(project: Mapping[str, Any], target: Any) -> List[Dict[str, str]]:
    return [_cmd("openwrt", "make world")]


def _build_alfs(project: Mapping[str, Any], target: Any) -> List[Dict[str, str]]:
    return [_cmd("alfs", "./build-lfs.sh")]


def _build_sourcemage(project: Mapping[str, Any], target: Any) -> List[Dict[str, str]]:
    return [_cmd("sorcery", "cast " + project["name"])]


def _build_lunar(project: Mapping[str, Any], target: Any) -> List[Dict[str, str]]:
    return [_cmd("lunar", "lunar build " + project["name"])]


# Dispatch table — single source of truth for build-system lookup.
# Adding a new system = one entry here. Unknown systems return [].
_SYSTEM_BUILDERS: Dict[str, Callable[[Mapping[str, Any], Any], List[Dict[str, str]]]] = {
    "gentoo":     _build_gentoo,
    "buildroot":  _build_buildroot,
    "openwrt":    _build_openwrt,
    "alfs":       _build_alfs,
    "sourcemage": _build_sourcemage,
    "lunar":      _build_lunar,
}


def generate_steps(project: Mapping[str, Any], target: Any) -> List[Dict[str, str]]:
    """Return the build steps for ``target`` under ``project``.

    Returns an empty list if ``target.system`` is unknown — this
    satisfies MISRA Rule 16.4 (switch shall have default).
    """
    system = getattr(target, "system", None) or (target.get("system") if isinstance(target, Mapping) else None)
    builder = _SYSTEM_BUILDERS.get(system)
    if builder is None:
        return []
    return builder(project, target)