"""
Shared helpers for loading a plugin headlessly.

Used by scripts/render_plugin.py, scripts/check_plugin.py, and the harness so
plugin discovery / manifest / config-default logic lives in exactly one place.
"""

import json
from pathlib import Path
from typing import Any, Dict, Optional, Sequence, Union


def find_plugin_dir(plugin_id: str, search_dirs: Sequence[Union[str, Path]]) -> Optional[Path]:
    """Find a plugin directory by searching multiple paths."""
    from src.plugin_system.plugin_loader import PluginLoader
    loader = PluginLoader()
    for search_dir in search_dirs:
        search_path = Path(search_dir)
        if not search_path.exists():
            continue
        result = loader.find_plugin_directory(plugin_id, search_path)
        if result:
            return Path(result)
    return None


def load_manifest(plugin_dir: Union[str, Path]) -> Dict[str, Any]:
    """Load and return manifest.json from a plugin directory."""
    manifest_path = Path(plugin_dir) / 'manifest.json'
    if not manifest_path.exists():
        raise FileNotFoundError(f"No manifest.json in {plugin_dir}")
    with open(manifest_path, 'r') as f:
        return json.load(f)


def load_config_defaults(plugin_dir: Union[str, Path]) -> Dict[str, Any]:
    """Extract default values from a plugin's config_schema.json (empty if none)."""
    schema_path = Path(plugin_dir) / 'config_schema.json'
    if not schema_path.exists():
        return {}
    with open(schema_path, 'r') as f:
        schema = json.load(f)
    defaults: Dict[str, Any] = {}
    for key, prop in schema.get('properties', {}).items():
        if isinstance(prop, dict) and 'default' in prop:
            defaults[key] = prop['default']
    return defaults


def load_harness_spec(plugin_dir: Union[str, Path]) -> Dict[str, Any]:
    """Optional per-plugin harness settings from <plugin>/test/harness.json.

    Lets a plugin opt into golden-image testing by declaring how to render it
    deterministically. All keys optional:
        {
          "config":     {...},            # config overrides
          "mock_data":  "fixtures/mock.json",  # path (relative to plugin dir) to cache fixtures
          "freeze_time": "2025-08-01 15:25:00",
          "skip_update": false,
          "fill_check": "warn",           # or "strict": underfilled big panels FAIL
          "variants": [                   # extra runs with config overlays and
            {                             # their own golden dirs — e.g. an
              "name": "adaptive",         # opt-in adaptive mode tested beside
              "config": {"layout_mode": "adaptive"},   # the classic default
              "golden_dir": "test/golden-adaptive"
            }
          ]
        }
    Returns {} when no harness.json exists.
    """
    spec_path = Path(plugin_dir) / 'test' / 'harness.json'
    if not spec_path.exists():
        return {}
    with open(spec_path, 'r') as f:
        spec = json.load(f)

    # Resolve mock_data path and inline its contents for convenience.
    mock_rel = spec.get('mock_data')
    if mock_rel:
        mock_path = Path(plugin_dir) / mock_rel
        if not mock_path.exists():
            # A declared-but-missing fixture is a harness config error: failing
            # loudly beats silently rendering the plugin with no mock data.
            raise FileNotFoundError(
                f"harness.json references mock_data '{mock_rel}' but "
                f"{mock_path} does not exist"
            )
        with open(mock_path, 'r') as mf:
            spec['mock_data_contents'] = json.load(mf)
    return spec


def build_full_config(
    plugin_dir: Union[str, Path],
    spec: Optional[Dict[str, Any]] = None,
    cli_config: Optional[Dict[str, Any]] = None,
) -> Dict[str, Any]:
    """Build the config a plugin sees under test.

    Merge order: config_schema.json defaults, then a forced ``enabled: True``,
    then harness.json's config overlay, then the caller's explicit config --
    most specific wins. `enabled` is re-asserted *after* the schema defaults
    so a plugin that reasonably ships `enabled: false` (e.g. a seasonal or
    opt-in plugin) can't silently make every harness run test "disabled, do
    nothing" by accident -- callers that genuinely want to test the disabled
    path can still do so via `cli_config={"enabled": False}`.
    """
    spec = spec or {}
    config: Dict[str, Any] = {}
    config.update(load_config_defaults(plugin_dir))
    config["enabled"] = True
    config.update(spec.get("config", {}))
    config.update(cli_config or {})
    return config