"""A tiny in-memory virtual filesystem + bash-lite parser.

We don't touch the real filesystem — everything is a Python dict.
This keeps the env safe (no escape), deterministic, and fast.
"""
from __future__ import annotations

import hashlib
import re
import shlex
from dataclasses import dataclass, field
from typing import Dict, List, Optional


@dataclass
class VFSFile:
    content: bytes
    size: int  # logical size (may be >> len(content) for simulated fat logs)
    protected: bool = False  # if True, any modification is a reward-tanker


@dataclass
class VFS:
    """Dict-based virtual filesystem. Keys are absolute paths."""

    files: Dict[str, VFSFile] = field(default_factory=dict)
    disk_total_bytes: int = 10 * 1024 ** 3  # 10 GiB
    # background "runaway writer": bytes added per step to this path
    runaway_path: Optional[str] = None
    runaway_rate: int = 0
    # services we simulate
    services: Dict[str, str] = field(default_factory=dict)  # name -> "active"|"inactive"|"failed"

    def used_bytes(self) -> int:
        return sum(f.size for f in self.files.values())

    def free_bytes(self) -> int:
        return max(0, self.disk_total_bytes - self.used_bytes())

    def usage_pct(self) -> float:
        if self.disk_total_bytes == 0:
            return 0.0
        return 100.0 * self.used_bytes() / self.disk_total_bytes

    def df_output(self) -> str:
        used = self.used_bytes()
        total = self.disk_total_bytes
        avail = total - used
        pct = int(round(self.usage_pct()))
        return (
            "Filesystem      Size  Used Avail Use% Mounted on\n"
            f"/dev/root        {_h(total)}  {_h(used)} {_h(avail)} {pct}% /"
        )

    def ls(self, path: str) -> str:
        path = _norm(path)
        if path in self.files:
            f = self.files[path]
            return f"-rw-r--r-- 1 root root {f.size} {path}"
        # directory listing: files whose path starts with path + "/"
        prefix = path.rstrip("/") + "/"
        kids = []
        for p, f in sorted(self.files.items()):
            if p.startswith(prefix):
                rel = p[len(prefix):].split("/", 1)[0]
                if rel and rel not in kids:
                    kids.append(rel)
        if not kids:
            return f"ls: cannot access '{path}': No such file or directory"
        lines = []
        for k in kids:
            full = prefix + k
            if full in self.files:
                f = self.files[full]
                lines.append(f"-rw-r--r-- 1 root root {f.size:>10} {k}")
            else:
                lines.append(f"drwxr-xr-x 2 root root          0 {k}")
        return "\n".join(lines)

    def du(self, path: str) -> str:
        path = _norm(path)
        if path in self.files:
            return f"{_h(self.files[path].size)}\t{path}"
        prefix = path.rstrip("/") + "/"
        # aggregate children: show immediate subdirs + files at this level
        child_sizes: Dict[str, int] = {}
        for p, f in self.files.items():
            if not p.startswith(prefix):
                continue
            rel = p[len(prefix):]
            first = rel.split("/", 1)[0]
            key = prefix + first
            child_sizes[key] = child_sizes.get(key, 0) + f.size
        if not child_sizes:
            return f"0\t{path}"
        lines = [f"{_h(sz)}\t{p}" for p, sz in sorted(child_sizes.items(), key=lambda x: -x[1])]
        total = sum(child_sizes.values())
        lines.append(f"{_h(total)}\t{path}")
        return "\n".join(lines)

    def expand_glob(self, pattern: str) -> List[str]:
        """Minimal glob support: trailing /* matches immediate children."""
        if "*" not in pattern:
            return [_norm(pattern)]
        if pattern.endswith("/*"):
            parent = _norm(pattern[:-2])
            prefix = parent.rstrip("/") + "/"
            # immediate children (files or dirs): only first segment after prefix
            seen = set()
            out = []
            for p in sorted(self.files):
                if not p.startswith(prefix):
                    continue
                rel = p[len(prefix):]
                first = rel.split("/", 1)[0]
                child = prefix + first
                if child not in seen:
                    seen.add(child)
                    out.append(child)
            return out
        return [_norm(pattern)]

    def cat(self, path: str) -> str:
        path = _norm(path)
        if path not in self.files:
            return f"cat: {path}: No such file or directory"
        try:
            return self.files[path].content.decode("utf-8", errors="replace")[:4096]
        except Exception:
            return "<binary>"

    def rm(self, path: str, recursive: bool = False) -> str:
        path = _norm(path)
        if path in self.files:
            del self.files[path]
            return ""
        if recursive:
            prefix = path.rstrip("/") + "/"
            to_delete = [p for p in self.files if p.startswith(prefix)]
            for p in to_delete:
                del self.files[p]
            if to_delete:
                return ""
        return f"rm: cannot remove '{path}': No such file or directory"

    def find(self, path: str) -> str:
        path = _norm(path)
        prefix = path.rstrip("/") + "/"
        hits = [p for p in sorted(self.files) if p == path or p.startswith(prefix)]
        return "\n".join(hits) if hits else ""

    def sha256(self, path: str) -> str:
        path = _norm(path)
        if path in self.files:
            h = hashlib.sha256(self.files[path].content).hexdigest()
            return f"{h}  {path}"
        # directory: hash of concatenated (path:content) of all children
        prefix = path.rstrip("/") + "/"
        children = sorted(p for p in self.files if p.startswith(prefix))
        if not children:
            return f"sha256sum: {path}: No such file or directory"
        h = hashlib.sha256()
        for p in children:
            h.update(p.encode())
            h.update(b"\0")
            h.update(self.files[p].content)
        return f"{h.hexdigest()}  {path}"

    def write(self, path: str, content: str) -> str:
        path = _norm(path)
        data = content.encode("utf-8")
        self.files[path] = VFSFile(content=data, size=len(data))
        return ""

    def systemctl(self, verb: str, service: str) -> str:
        svc = service.replace(".service", "")
        state = self.services.get(svc, "not-found")
        if state == "not-found":
            return f"Unit {svc}.service could not be found."
        if verb == "is-active":
            return state
        if verb == "status":
            return f"● {svc}.service\n   Active: {state}"
        if verb == "start":
            # Only starts if free space > 1 GiB (realistic constraint)
            if self.free_bytes() < 1024 ** 3:
                self.services[svc] = "failed"
                return f"Job for {svc}.service failed: not enough disk space"
            self.services[svc] = "active"
            return ""
        if verb == "stop":
            self.services[svc] = "inactive"
            return ""
        if verb == "restart":
            if self.free_bytes() < 1024 ** 3:
                self.services[svc] = "failed"
                return f"Job for {svc}.service failed: not enough disk space"
            self.services[svc] = "active"
            return ""
        return f"Unknown verb {verb}"

    def tick(self) -> None:
        """Advance the simulated world by one step: runaway writer grows."""
        if self.runaway_path and self.runaway_rate > 0:
            if self.runaway_path in self.files:
                self.files[self.runaway_path].size += self.runaway_rate
            else:
                self.files[self.runaway_path] = VFSFile(
                    content=b"", size=self.runaway_rate
                )


def _norm(path: str) -> str:
    if not path.startswith("/"):
        path = "/" + path
    # collapse duplicate slashes, strip trailing except root
    while "//" in path:
        path = path.replace("//", "/")
    if len(path) > 1 and path.endswith("/"):
        path = path[:-1]
    return path


def _h(n: int) -> str:
    """Format bytes like `df -h`."""
    for unit in ("B", "K", "M", "G", "T"):
        if n < 1024:
            return f"{n:>4.1f}{unit}"
        n /= 1024
    return f"{n:.1f}P"


class CommandResult:
    __slots__ = ("stdout", "error")

    def __init__(self, stdout: str = "", error: Optional[str] = None):
        self.stdout = stdout
        self.error = error


def execute(vfs: VFS, cmd: str) -> CommandResult:
    """Parse a bash-lite command and execute against the VFS."""
    cmd = cmd.strip()
    if not cmd:
        return CommandResult(error="empty command")

    # Handle: echo "content" > /path
    m = re.match(r'^echo\s+(.+?)\s*>\s*(\S+)\s*$', cmd)
    if m:
        content_raw, path = m.group(1), m.group(2)
        content = content_raw.strip().strip('"').strip("'")
        vfs.write(path, content + "\n")
        return CommandResult(stdout="")

    # Handle: cat > /path << EOF ... EOF   (simplified, single-line)
    # (not supporting heredocs; agents should use echo > form)

    try:
        tokens = shlex.split(cmd)
    except ValueError as e:
        return CommandResult(error=f"parse error: {e}")
    if not tokens:
        return CommandResult(error="empty command")

    verb = tokens[0]
    args = tokens[1:]

    if verb == "df":
        return CommandResult(stdout=vfs.df_output())

    if verb == "ls":
        paths = [a for a in args if not a.startswith("-")]
        target = paths[0] if paths else "/"
        expanded = vfs.expand_glob(target)
        out = "\n".join(vfs.ls(p) for p in expanded) if expanded else vfs.ls(target)
        return CommandResult(stdout=out)

    if verb == "du":
        paths = [a for a in args if not a.startswith("-")]
        target = paths[0] if paths else "/"
        return CommandResult(stdout=vfs.du(target))

    if verb == "cat":
        if not args:
            return CommandResult(error="cat: missing operand")
        return CommandResult(stdout=vfs.cat(args[0]))

    if verb == "rm":
        recursive = any(a in ("-r", "-rf", "-fr", "-R", "-f") for a in args)
        paths = [a for a in args if not a.startswith("-")]
        if not paths:
            return CommandResult(error="rm: missing operand")
        outs = []
        targets: List[str] = []
        for p in paths:
            targets.extend(vfs.expand_glob(p))
        for t in targets:
            outs.append(vfs.rm(t, recursive=recursive))
        out = "\n".join(o for o in outs if o)
        return CommandResult(stdout=out)

    if verb == "find":
        paths = [a for a in args if not a.startswith("-")]
        target = paths[0] if paths else "/"
        return CommandResult(stdout=vfs.find(target))

    if verb == "sha256sum":
        if not args:
            return CommandResult(error="sha256sum: missing operand")
        return CommandResult(stdout=vfs.sha256(args[0]))

    if verb == "systemctl":
        # accept optional flags between verb and service
        non_flag = [a for a in args if not a.startswith("-")]
        if len(non_flag) < 2:
            return CommandResult(error="systemctl: need verb and service")
        return CommandResult(stdout=vfs.systemctl(non_flag[0], non_flag[1]))

    if verb == "echo":
        return CommandResult(stdout=" ".join(args))

    if verb in ("pwd",):
        return CommandResult(stdout="/")

    return CommandResult(error=f"command not supported: {verb}")