"""
VyOSModule — high-level wrapper used by vyos.rest resource modules.

Provides ``get_config()``, ``apply_commands()``, and ``save_config()``
on top of ``VyOSRestClient``, so resource modules can work with simple
``("set", path)`` / ``("delete", path)`` command tuples rather than
calling the REST client directly.
"""

from __future__ import absolute_import, division, print_function


__metaclass__ = type

from ansible_collections.vyos.rest.plugins.module_utils.vyos_rest import (
    VyOSRestClient,
    VyOSRestError,
)


# ---------------------------------------------------------------------------
# Legacy dynamic config utilities (used by Wave 1-3 modules)
# ---------------------------------------------------------------------------


def _kebab_to_snake(s):
    """Convert kebab-case string to snake_case."""
    return s.replace("-", "_")


def _snake_to_kebab(s):
    """Convert snake_case string to kebab-case."""
    return s.replace("_", "-")


def normalize(raw):
    """Recursively normalize an API response dict to snake_case keys."""
    if isinstance(raw, dict):
        return {_kebab_to_snake(k): normalize(v) for k, v in raw.items()}
    if isinstance(raw, list):
        return [normalize(v) for v in raw]
    return raw


def denormalize_path(path):
    """Convert a snake_case path list to kebab-case for the API."""
    return [_snake_to_kebab(p) for p in path]


def _diff_value(want_val, have_val, path, cmds, delete_missing):
    if isinstance(want_val, dict):
        if not want_val:
            if not have_val:
                cmds.append(("set", denormalize_path(path)))
        else:
            have_dict = have_val if isinstance(have_val, dict) else {}
            _diff_dict(want_val, have_dict, path, cmds, delete_missing)
    elif isinstance(want_val, list):
        have_set = set(have_val) if isinstance(have_val, list) else set()
        for item in want_val:
            if item not in have_set:
                cmds.append(("set", denormalize_path(path + [str(item)])))
        if delete_missing:
            want_set = set(str(i) for i in want_val)
            for item in have_val or []:
                if str(item) not in want_set:
                    cmds.append(("delete", denormalize_path(path + [str(item)])))
    else:
        if want_val != have_val:
            cmds.append(("set", denormalize_path(path + [str(want_val)])))


def _diff_dict(want, have, path, cmds, delete_missing):
    for key, want_val in want.items():
        _diff_value(want_val, have.get(key), path + [key], cmds, delete_missing)
    if delete_missing:
        for key in have:
            if key not in want:
                cmds.append(("delete", denormalize_path(path + [key])))


def diff_configs(want, have, base_path, delete_missing=False):
    """Diff two normalized config dicts and return API command tuples.

    Args:
        want (dict): Desired configuration (snake_case keys).
        have (dict): Current configuration (snake_case keys).
        base_path (list): Base API path for commands.
        delete_missing (bool): Generate delete commands for keys in
            ``have`` absent from ``want``.

    Returns:
        list: Tuples of ``("set", path)`` or ``("delete", path)``.
    """
    cmds = []
    _diff_dict(want, have, base_path, cmds, delete_missing)
    return cmds


# ---------------------------------------------------------------------------
# Generic dict diff engine (used by Wave 4+ modules)
#
# Design principles:
#   - want uses snake_case (from YAML/argspec)
#   - have uses kebab-case (from device API)
#   - Conversion between - and _ happens here, once, in the core
#   - Modules only need _BASE path — no key mapping anywhere
#   - want is the reference dataset — drives all operations
# ---------------------------------------------------------------------------


def owned_config(have, argspec):
    """Filter raw device config to only keys owned by this module.

    Ownership is declared by the module's argspec — the single source
    of truth for what this module manages. Keys in have not present in
    argspec (after normalization) are excluded from before/after output.

    Args:
        have (dict): Raw device config (kebab-case keys).
        argspec (dict): Module argument_spec dict.

    Returns:
        dict: Filtered have with only module-owned keys.
    """
    owned = set(argspec.keys()) - {"state"}
    return {k: v for k, v in have.items() if k.replace("-", "_") in owned}


def dict_op(want, have, base_path, op="set"):
    """Generic dict diff engine for VyOS REST API.

    Compares want (snake_case, from YAML) against have (kebab-case, from
    device) and generates API command tuples. All key normalization between
    snake_case and kebab-case happens here — modules never need to convert.

    Set operations on the two datasets:
        op="set"    want - have       present: apply what is missing
        op="delete" want ∩ have       absent:  remove what exists
        op="purge"  have - want       replaced: remove what is extra

    Args:
        want (dict): Desired config, snake_case keys (from YAML/argspec).
        have (dict): Current config, kebab-case keys (raw from device API).
        base_path (list): Base API path — the only module-specific knowledge.
        op (str): "set", "delete", or "purge".

    Returns:
        list: Tuples of ("set", path) or ("delete", path).
    """
    cmds = []

    # Index have by normalized key for O(1) lookup.
    # Preserves original kebab-case key for use in API paths.
    have_idx = {k.replace("-", "_"): (k, v) for k, v in (have or {}).items()}

    if op == "purge":
        # have - want: delete have keys not present in want
        # Scoped naturally by _BASE — only this subtree is in have
        want_keys = {k.replace("-", "_") for k in (want or {})}
        for norm_k, (orig_k, have_v) in have_idx.items():
            if norm_k not in want_keys:
                cmds.append(("delete", base_path + [orig_k]))
        return cmds

    for key, want_val in (want or {}).items():
        if want_val is None:
            continue

        # Normalize want key for lookup, get original device key for path
        norm_key = key.replace("-", "_")
        orig_key, have_val = have_idx.get(norm_key, (key.replace("_", "-"), None))
        path = base_path + [orig_key]

        if isinstance(want_val, dict):
            if not want_val:
                # Presence node
                if op == "set" and not have_val:
                    cmds.append(("set", path))
                elif op == "delete" and have_val is not None:
                    cmds.append(("delete", path))
            else:
                # Recurse — have_val passed raw, conversion happens recursively
                cmds += dict_op(want_val, have_val or {}, path, op)

        elif isinstance(want_val, list):
            # Device may return a single value as a string instead of a list
            if isinstance(have_val, str):
                have_val = [have_val]
            have_set = set(str(i) for i in (have_val or []))
            if op == "set":
                # want - have: add missing items
                for item in want_val:
                    if str(item) not in have_set:
                        cmds.append(("set", path + [str(item)]))
            elif op == "delete":
                # want ∩ have: remove items that exist
                for item in want_val:
                    if str(item) in have_set:
                        cmds.append(("delete", path + [str(item)]))

        else:
            # Scalar leaf
            have_str = str(have_val) if have_val is not None else ""
            if op == "set" and str(want_val) != have_str:
                cmds.append(("set", path + [str(want_val)]))
            elif op == "delete" and have_val is not None:
                cmds.append(("delete", path))

    return cmds


class VyOSModule:
    """Thin wrapper around VyOSRestClient for resource modules."""

    def __init__(self, module):
        self._module = module
        self._client = VyOSRestClient(module)

    def get_config(self, path=None):
        """Retrieve the configuration subtree at *path*.

        Returns raw device dict with kebab-case keys.
        """
        try:
            result = self._client.retrieve_show_config(path or [])
            return result.get("data") or {}
        except VyOSRestError:
            return {}

    def apply_commands(self, commands):
        if not commands:
            return []
        payload = []
        for cmd in commands:
            if isinstance(cmd, dict):
                op, path = cmd["op"], list(cmd["path"])
            else:
                op, path = cmd[0], list(cmd[1])
            payload.append({"op": op, "path": path})
        try:
            return self._client.configure_batch(payload)
        except VyOSRestError as exc:
            self._module.fail_json(
                msg="apply_commands failed: {e}".format(e=str(exc)),
            )

    def _apply_set(self, path, value=None):
        """Set a config path, retrying with a shortened path on failure."""
        try:
            self._client.configure_set(path, value)
            return {"op": "set", "path": path, "status": "ok"}
        except VyOSRestError as exc:
            if len(path) >= 3:
                short_path = path[:-2] + [path[-1]]
                try:
                    self._client.configure_set(short_path, value)
                    return {"op": "set", "path": short_path, "status": "ok-adapted"}
                except VyOSRestError:
                    pass
            raise VyOSRestError(
                "set {p} failed: {e}".format(p=" ".join(path), e=str(exc)),
            )

    def _apply_delete(self, path):
        """Delete a config path; silently ignore if already absent."""
        try:
            self._client.configure_delete(path)
            return {"op": "delete", "path": path, "status": "ok"}
        except VyOSRestError:
            return {"op": "delete", "path": path, "status": "noop"}

    def show(self, path):
        """Run an operational show command via the /show endpoint."""
        try:
            result = self._client.show(path)
            return result.get("data") or ""
        except VyOSRestError:
            return ""

    def save_config(self, file_path=None):
        """Save the running configuration to disk."""
        try:
            self._client.config_file_save(file_path)
            return True
        except VyOSRestError:
            return False