"""Knoe configuration environment management.

This module centralizes how Knoe resolves configuration paths and how it
loads configuration with per-environment layering.

Target on-disk layout (under `$KNOE_CONF`):

- `k3d.cfg` -> local development configuration
- `k3s.cfg` -> k3s/service configuration
- `gke.cfg` -> production/GKE configuration

Legacy `knoe.cfg` and `conf/<env>/knoe.cfg` paths are still recognized for
backward compatibility.
"""

from __future__ import annotations

import configparser
import os
import time
from pathlib import Path

ENVIRONMENTS: tuple[str, ...] = ("dev", "service", "prod", "test")
ENV_TO_CFG_FILE: dict[str, str] = {
    "dev": "k3d.cfg",
    "service": "k3s.cfg",
    "prod": "gke.cfg",
    "test": "test.cfg",
}
CFG_FILE_TO_ENV: dict[str, str] = {cfg: env for env, cfg in ENV_TO_CFG_FILE.items()}
PREFERRED_CFG_ORDER: tuple[str, ...] = ("k3d.cfg", "k3s.cfg", "gke.cfg", "test.cfg")


def cfg_file_for_env(env: str | None) -> str:
    env_key = normalize_environment(env)
    return ENV_TO_CFG_FILE.get(env_key, "")


def env_for_cfg_file(name: str | None) -> str:
    if not name:
        return ""
    return CFG_FILE_TO_ENV.get(str(name).strip().lower(), "")


def _env_from_mode_or_env_hint(raw: str | None) -> str:
    """Map a mode/env hint to one of the supported environments."""

    s = normalize_environment(raw or "")
    if not s:
        return ""
    # normalize_environment already maps k3d/k3s/k8s-ish values to env names.
    if s in ENVIRONMENTS:
        return s
    return ""


def _infer_env_from_cfg_file(cfg_path: Path) -> str:
    """Best-effort inference of active env from a legacy standalone knoe.cfg."""

    cfg_path = Path(cfg_path)
    if not cfg_path.exists() or not cfg_path.is_file() or cfg_path.is_symlink():
        return ""

    try:
        cfg = configparser.ConfigParser(interpolation=None)
        cfg.optionxform = str
        cfg.read([str(cfg_path)])
    except Exception:
        return ""

    # Priority order: explicit deployment mode -> explicit env -> UI/inputs hints.
    for section, key in (
        ("Global", "DEPLOYMENT_MODE"),
        ("Global", "MODE"),
        ("Global", "CLUSTER_ENV"),
        ("Initialize Cluster", "ENVIRONMENT"),
        ("Inputs", "init_cluster.mode"),
        ("Inputs", "init_cluster.cluster_env"),
    ):
        try:
            if cfg.has_section(section):
                env = _env_from_mode_or_env_hint(cfg.get(section, key, fallback=""))
                if env:
                    return env
        except Exception:
            continue
    return ""


def normalize_environment(env: str | None) -> str:
    if not env:
        return ""
    s = str(env).strip().lower()
    if s in ("dev", "k3d") or s.startswith(("k3d-", "knoe-dev-")) or s == "knoe-dev-cluster":
        return "dev"
    if s in ("service", "services", "k3s", "knoe-service-cluster") or s.startswith("knoe-service-"):
        return "service"
    if s in ("prod", "production", "k8s", "knoe-prod-cluster") or s.startswith(("knoe-prod-", "gke_")):
        return "prod"
    if s in ("test", "testing"):
        return "test"
    return s


def resolve_knoe_conf_dir(project_root: Path) -> Path:
    raw = os.environ.get("KNOE_CONF", "").strip()
    if raw:
        return Path(raw).expanduser()
    return project_root / "conf"


def entrypoint_path(conf_dir: Path) -> Path:
    """Return the active configuration file path.

    Prefers named root config files (`k3d.cfg`, `k3s.cfg`, `gke.cfg`) resolved
    from CLUSTER_ENV/KNOE_MODE/DEPLOYMENT_MODE. Falls back to legacy env-dir
    `knoe.cfg` files and finally `conf/knoe.cfg` for compatibility.
    """
    conf_dir = Path(conf_dir)
    # Determine active env from environment variables (set by the UI on save).
    for var in ("CLUSTER_ENV", "KNOE_MODE", "DEPLOYMENT_MODE"):
        hint = os.environ.get(var, "").strip()
        if hint:
            env = _env_from_mode_or_env_hint(hint)
            if env in ENVIRONMENTS:
                named = cfg_file_for_env(env)
                if named:
                    named_path = conf_dir / named
                    if named_path.exists():
                        return named_path
                env_path = conf_dir / env / "knoe.cfg"
                if env_path.exists():
                    return env_path

    for cfg_name in PREFERRED_CFG_ORDER:
        path = conf_dir / cfg_name
        if path.exists():
            return path

    for env in ENVIRONMENTS:
        env_path = conf_dir / env / "knoe.cfg"
        if env_path.exists():
            return env_path

    legacy = conf_dir / "knoe.cfg"
    if legacy.exists():
        return legacy

    # Default target when creating a fresh config.
    return conf_dir / "k3d.cfg"


def _is_known_env_dir(conf_dir: Path, env_dir: Path) -> bool:
    try:
        return env_dir.is_dir() and env_dir.parent.resolve() == conf_dir.resolve() and env_dir.name in ENVIRONMENTS
    except Exception:
        return False


def resolve_env_dir_from_cfg_path(cfg_path: Path) -> tuple[Path, str, Path]:
    """Return (conf_dir, env_name, env_dir).

    Supports:
    - `$KNOE_CONF/{k3d.cfg|k3s.cfg|gke.cfg|test.cfg}` base files
    - legacy `$KNOE_CONF/knoe.cfg` entrypoint (symlink/plain)
    - legacy `$KNOE_CONF/<env>/knoe.cfg` base files
    """

    cfg_path = Path(cfg_path)

    # New layout: named config directly in conf dir.
    env_from_name = env_for_cfg_file(cfg_path.name)
    if env_from_name:
        return cfg_path.parent, env_from_name, cfg_path.parent / env_from_name

    # If cfg_path is an entrypoint symlink, resolve its target.
    try:
        if cfg_path.is_symlink():
            target = cfg_path.resolve()
            target_env_from_name = env_for_cfg_file(target.name)
            if target_env_from_name:
                return target.parent, target_env_from_name, target.parent / target_env_from_name
            env_dir = target.parent
            conf_dir = env_dir.parent
            env = normalize_environment(env_dir.name)
            expected = cfg_file_for_env(env)
            if env and _is_known_env_dir(conf_dir, env_dir) and target.name in {"knoe.cfg", expected}:
                return conf_dir, env, env_dir
    except Exception:
        pass

    # If cfg_path is already a base file inside an env dir.
    try:
        env_dir = cfg_path.parent
        conf_dir = env_dir.parent
        env = normalize_environment(env_dir.name)
        expected = cfg_file_for_env(env)
        if env and env in ENVIRONMENTS and cfg_path.name in {"knoe.cfg", expected} and _is_known_env_dir(conf_dir, env_dir):
            return conf_dir, env, env_dir
    except Exception:
        pass

    # Fallback: treat as a standalone file.
    return cfg_path.parent, "", cfg_path.parent


def layered_cfg_files(cfg_path: Path) -> list[Path]:
    """Return config files to load in order (base then overrides)."""
    cfg_path = Path(cfg_path)
    conf_dir, env, env_dir = resolve_env_dir_from_cfg_path(cfg_path)

    files: list[Path] = []

    # New layout uses single named config files in conf dir (no overlays).
    if env_for_cfg_file(cfg_path.name):
        files.append(cfg_path)
        return files

    if env and _is_known_env_dir(conf_dir, env_dir):
        base_name = cfg_file_for_env(env)
        base = env_dir / base_name if base_name else env_dir / "knoe.cfg"
        if not base.exists():
            base = env_dir / "knoe.cfg"
        if base.exists():
            files.append(base)
        try:
            skip_names = {
                "prod.cfg",  # standalone deploy config, not an overlay for knoe.cfg
                "gcp.cfg",   # generated metadata file (key=value, no INI sections)
            }
            overrides = [
                p
                for p in env_dir.iterdir()
                if p.is_file()
                and p.name != base.name
                and p.name not in skip_names
                and p.suffix == ".cfg"
                and not p.name.startswith(".")
            ]
            overrides.sort(key=lambda p: p.name)
            files.extend(overrides)
        except Exception:
            pass
        if files:
            return files

    # Legacy/standalone: load only the given path.
    files.append(cfg_path)
    return files


def load_layered_config(cfg_path: Path, require_exists: bool = False) -> configparser.ConfigParser:
    """Load config from `cfg_path` applying env directory overrides if applicable."""

    cfg_path = Path(cfg_path)
    if require_exists and not cfg_path.exists():
        raise FileNotFoundError(str(cfg_path))

    cfg = configparser.ConfigParser(interpolation=None)
    cfg.optionxform = str

    files = [p for p in layered_cfg_files(cfg_path) if p.exists()]
    if files:
        cfg.read([str(p) for p in files])
    return cfg


def ensure_environment_dirs(conf_dir: Path) -> None:
    conf_dir = Path(conf_dir)
    conf_dir.mkdir(parents=True, exist_ok=True)
    for env in ENVIRONMENTS:
        try:
            (conf_dir / env).mkdir(parents=True, exist_ok=True)
        except Exception:
            pass


def _default_base_cfg_text(env: str) -> str:
    env = normalize_environment(env)
    if env not in ENVIRONMENTS:
        env = "dev"

    # Keep defaults conservative and compatible with prior single-file defaults:
    # - non-test uses a stable DB namespace default
    # - test is isolated
    if env == "test":
        database_ns = "knoe-test"
        service_ns = "knoe-test"
        cluster_name = "knoe-db"
    elif env == "dev":
        database_ns = "knoe-db"
        service_ns = "default"
        cluster_name = "knoe-db"
    else:
        database_ns = "knoe-db"
        service_ns = "knoe-system"
        cluster_name = "knoe-db"

    return (
        "; Knoe Master Configuration File\n"
        "; Generated by knoe_conf\n\n"
        "[Global]\n"
        f"CLUSTER_ENV = {env}\n"
        f"NAMESPACE = {database_ns}\n"
        f"DATABASE_NAMESPACE = {database_ns}\n"
        f"SERVICE_NAMESPACE = {service_ns}\n"
        f"CLUSTER_NAME = {cluster_name}\n"
    )


def _looks_like_generated_base_cfg(path: Path, env: str) -> bool:
    """True if `path` looks like a default knoe_conf-generated base."""

    path = Path(path)
    if not path.exists() or not path.is_file():
        return False
    try:
        cfg = configparser.ConfigParser(interpolation=None)
        cfg.optionxform = str
        cfg.read([str(path)])
        if cfg.sections() != ["Global"]:
            return False
        return _env_from_mode_or_env_hint(cfg.get("Global", "CLUSTER_ENV", fallback="")) == env
    except Exception:
        return False


def ensure_base_cfg(conf_dir: Path, env: str, *, create_if_missing: bool = True) -> Path:
    conf_dir = Path(conf_dir)
    env_key = normalize_environment(env)
    if env_key not in ENVIRONMENTS:
        raise ValueError(f"Unsupported environment: {env!r}")
    # Primary location: conf/{env}/knoe.cfg (env-dir layout)
    env_dir = conf_dir / env_key
    env_dir.mkdir(parents=True, exist_ok=True)
    base = env_dir / "knoe.cfg"
    if not base.exists() and create_if_missing:
        base.write_text(_default_base_cfg_text(env_key), encoding="utf-8")
    return base


def activate_environment(
    conf_dir: Path,
    env: str,
    *,
    create_base_if_missing: bool = True,
    migrate_legacy_entrypoint: bool = True,
) -> Path:
    """Activate `env` and return its named root config path.

    Sets CLUSTER_ENV in the process environment so that subsequent
    entrypoint_path() calls resolve the correct config without
    needing a conf/knoe.cfg symlink.
    This never overwrites another environment's curated config.
    """

    conf_dir = Path(conf_dir)
    env_key = normalize_environment(env)
    if env_key not in ENVIRONMENTS:
        raise ValueError(f"Unsupported environment: {env!r}")

    ensure_environment_dirs(conf_dir)
    base = ensure_base_cfg(conf_dir, env_key, create_if_missing=create_base_if_missing)

    # Migrate any legacy plain-file entrypoint into the target base.
    if migrate_legacy_entrypoint:
        legacy_entry = conf_dir / "knoe.cfg"
        if legacy_entry.exists() and not legacy_entry.is_symlink():
            try:
                legacy_text = legacy_entry.read_text(encoding="utf-8")
                if not base.exists() or _looks_like_generated_base_cfg(base, env_key) or not base.read_text(
                    encoding="utf-8", errors="ignore"
                ).strip():
                    base.write_text(legacy_text, encoding="utf-8")
                legacy_name = f"knoe.cfg.legacy.{int(time.time())}"
                legacy_entry.rename(conf_dir / legacy_name)
            except Exception:
                pass

        # Migrate legacy env-dir base into new named root config when helpful.
        legacy_env_base = conf_dir / env_key / "knoe.cfg"
        if legacy_env_base.exists() and legacy_env_base.is_file():
            try:
                legacy_text = legacy_env_base.read_text(encoding="utf-8")
                if not base.exists() or _looks_like_generated_base_cfg(base, env_key) or not base.read_text(
                    encoding="utf-8", errors="ignore"
                ).strip():
                    base.write_text(legacy_text, encoding="utf-8")
            except Exception:
                pass

    if not base.exists() and create_base_if_missing:
        base.write_text(_default_base_cfg_text(env_key), encoding="utf-8")

    if not base.exists():
        raise FileNotFoundError(str(base))

    # Create / update conf/knoe.cfg as a symlink pointing to the active env base.
    entry = conf_dir / "knoe.cfg"
    try:
        if entry.exists() or entry.is_symlink():
            if entry.is_symlink():
                entry.unlink()
            elif entry.is_file():
                # Back up any remaining plain file before replacing with symlink.
                legacy_name = f"knoe.cfg.legacy.{int(time.time())}"
                entry.rename(conf_dir / legacy_name)
        entry.symlink_to(base)
    except Exception:
        pass

    # Persist the active environment in the process so entrypoint_path() resolves
    # conf/{env}/knoe.cfg without a conf/knoe.cfg symlink.
    os.environ["CLUSTER_ENV"] = env_key
    return base


def ensure_entrypoint(
    conf_dir: Path,
    *,
    preferred_env: str | None = None,
    create_base_if_missing: bool = True,
) -> Path:
    """Ensure the active named config exists and return its path.

    - Creates missing env directories.
    - Infers the environment from preferred_env, env vars, or existing config.
    - If the env-specific base is missing, creates a default placeholder.

    Returns the resolved config path (e.g. conf/k3d.cfg).
    """

    conf_dir = Path(conf_dir)
    ensure_environment_dirs(conf_dir)

    env = _env_from_mode_or_env_hint(preferred_env)
    if not env:
        # Try to infer from the legacy plain-file entrypoint if it still exists.
        legacy = conf_dir / "knoe.cfg"
        if legacy.exists() and not legacy.is_symlink():
            env = _infer_env_from_cfg_file(legacy)
    if not env:
        for cfg_name in PREFERRED_CFG_ORDER:
            if (conf_dir / cfg_name).exists():
                env = env_for_cfg_file(cfg_name)
                if env:
                    break
    if not env:
        env = "dev"

    return activate_environment(
        conf_dir,
        env,
        create_base_if_missing=create_base_if_missing,
        migrate_legacy_entrypoint=True,
    )


def active_environment(conf_dir: Path) -> str:
    """Return the currently active environment name.

    Resolves from CLUSTER_ENV/KNOE_MODE env vars first (set by activate_environment),
    then falls back to inferring from the resolved config file path.
    """
    conf_dir = Path(conf_dir)
    for var in ("CLUSTER_ENV", "KNOE_MODE", "DEPLOYMENT_MODE"):
        hint = os.environ.get(var, "").strip()
        if hint:
            env = _env_from_mode_or_env_hint(hint)
            if env in ENVIRONMENTS:
                return env
    entry = entrypoint_path(conf_dir)
    if not entry.exists():
        return ""

    env = env_for_cfg_file(entry.name)
    if env in ENVIRONMENTS:
        return env

    try:
        target = entry.resolve()
        env = env_for_cfg_file(target.name)
        if env in ENVIRONMENTS:
            return env
        env = normalize_environment(target.parent.name)
        expected = cfg_file_for_env(env)
        if env in ENVIRONMENTS and _is_known_env_dir(conf_dir, target.parent) and target.name in {"knoe.cfg", expected}:
            return env
    except Exception:
        pass
    return ""