"""Environment auto-discovery for the onboarding wizard.

All checks are best-effort — every function returns an empty list on failure
so the wizard degrades gracefully in containers, VMs, and minimal environments.
"""
from __future__ import annotations

import json
import logging
import os
import shutil
import subprocess
from pathlib import Path
from typing import Any

logger = logging.getLogger(__name__)

# Common log file candidates: (id, path, description)
_KNOWN_PATHS: list[tuple[str, str, str]] = [
    ("syslog",       "/var/log/syslog",              "System syslog (Debian/Ubuntu)"),
    ("syslog",       "/var/log/messages",             "System messages (RHEL/Rocky)"),
    ("auth",         "/var/log/auth.log",             "Auth log"),
    ("kern",         "/var/log/kern.log",             "Kernel log"),
    ("nginx-access", "/var/log/nginx/access.log",     "Nginx access log"),
    ("nginx-error",  "/var/log/nginx/error.log",      "Nginx error log"),
    ("apache",       "/var/log/apache2/access.log",   "Apache access log"),
    ("apache-error", "/var/log/apache2/error.log",    "Apache error log"),
    ("caddy",        "/var/log/caddy/access.log",     "Caddy access log"),
    ("docker-daemon","/var/log/docker.log",           "Docker daemon log"),
    ("fail2ban",     "/var/log/fail2ban.log",         "Fail2ban log"),
    ("ufw",          "/var/log/ufw.log",              "UFW firewall log"),
]


def _run(cmd: list[str], timeout: float = 5.0) -> str | None:
    """Run a command and return stdout, or None on any error."""
    try:
        result = subprocess.run(cmd, capture_output=True, text=True, timeout=timeout)
        return result.stdout if result.returncode == 0 else None
    except Exception:
        return None


def discover_journald() -> list[dict[str, Any]]:
    """Return a journald source candidate if journalctl is available."""
    if not shutil.which("journalctl"):
        return []
    hostname = _run(["hostname"]) or "localhost"
    hostname = hostname.strip()
    return [{
        "type": "journald",
        "id": f"journal:{hostname}",
        "label": f"System journal ({hostname})",
        "description": "All systemd journal output from this host",
        "available": True,
    }]


def discover_docker() -> list[dict[str, Any]]:
    """Return Docker container candidates if Docker is running."""
    for runtime in ("docker", "podman"):
        if not shutil.which(runtime):
            continue
        out = _run([runtime, "ps", "--format", "{{json .}}"])
        if out is None:
            continue
        containers = []
        for line in out.splitlines():
            line = line.strip()
            if not line:
                continue
            try:
                obj = json.loads(line)
                name = obj.get("Names") or obj.get("Name") or obj.get("ID", "unknown")
                # podman returns a list for Names
                if isinstance(name, list):
                    name = name[0] if name else "unknown"
                name = name.lstrip("/")
                containers.append({
                    "type": "docker",
                    "id": f"{runtime}:{name}",
                    "label": f"{runtime.capitalize()} — {name}",
                    "description": f"Container log stream for {name}",
                    "container": name,
                    "runtime": runtime,
                    "available": True,
                })
            except (json.JSONDecodeError, KeyError):
                continue
        if containers:
            return containers
    return []


def discover_files() -> list[dict[str, Any]]:
    """Return file-based source candidates for well-known log paths."""
    found = []
    seen_ids: set[str] = set()
    for source_id, path, description in _KNOWN_PATHS:
        if not os.path.exists(path):
            continue
        # deduplicate when both syslog and messages exist — take first match
        if source_id in seen_ids:
            continue
        seen_ids.add(source_id)
        found.append({
            "type": "file",
            "id": source_id,
            "label": description,
            "path": path,
            "description": f"Read from {path}",
            "available": True,
        })
    return found


def discover_all() -> dict[str, Any]:
    """Run all discovery checks and return a structured candidate list."""
    candidates: list[dict[str, Any]] = []
    candidates.extend(discover_journald())
    candidates.extend(discover_docker())
    candidates.extend(discover_files())
    return {
        "candidates": candidates,
        "has_journald": any(c["type"] == "journald" for c in candidates),
        "has_docker":   any(c["type"] == "docker"   for c in candidates),
        "has_files":    any(c["type"] == "file"      for c in candidates),
    }


def build_sources_yaml(selected: list[dict[str, Any]]) -> str:
    """Generate sources.yaml content from a list of selected candidates.

    Each item must have: type, id, and type-specific fields (path, container, etc.).
    """
    lines = [
        "# Turnstone log sources — generated by the setup wizard.",
        "# Edit this file to add, remove, or modify sources.",
        "sources:",
    ]
    for src in selected:
        src_type = src.get("type", "file")
        src_id = src.get("id", "unknown")
        if src_type == "journald":
            unit = src.get("unit")
            lines.append(f"  - id: {src_id}")
            lines.append(f"    type: journald")
            if unit:
                lines.append(f"    unit: {unit}")
        elif src_type == "docker":
            runtime = src.get("runtime", "docker")
            container = src.get("container", src_id.split(":")[-1])
            lines.append(f"  - id: {src_id}")
            lines.append(f"    type: docker")
            lines.append(f"    runtime: {runtime}")
            lines.append(f"    container: {container}")
        else:
            path = src.get("path", "")
            lines.append(f"  - id: {src_id}")
            lines.append(f"    path: {path}")
    return "\n".join(lines) + "\n"


def validate_source(src: dict[str, Any]) -> str | None:
    """Return an error string if the source definition is invalid, else None."""
    if not src.get("id"):
        return "Source is missing 'id'"
    src_type = src.get("type", "file")
    if src_type == "file" and not src.get("path"):
        return f"File source '{src['id']}' is missing 'path'"
    if src_type == "docker" and not src.get("container"):
        return f"Docker source '{src['id']}' is missing 'container'"
    return None