"""Import sessions from foreign coding agents (Claude Code, Codex CLI). Foreign files are only ever read;
imported history must satisfy the provider role-alternation invariant (see ``_merge_turns``)."""

from __future__ import annotations

import contextlib
import json
import os
import re
import sys
from dataclasses import dataclass
from datetime import datetime
from pathlib import Path
from stat import S_ISREG
from typing import Any, Dict, List, Optional, Tuple

from hermes_state_ids import new_session_id

# User-message texts that are really injected context wrappers, not typed input.
_WRAPPER_TAG_RE = re.compile(
    r"^<(?:user_instructions|environment_context|recommended_plugins|"
    r"skills_instructions|permissions[_-]instructions|turn_context|"
    r"command-name|command-message|local-command-stdout|system-reminder)\b", re.IGNORECASE)

_TITLE_MAX = 60
_SOURCE_LABELS = {"claude": "Claude Code", "codex": "Codex CLI"}
_SOURCE_DB_NAMES = {"claude": "claude-code", "codex": "codex-cli"}


@dataclass
class ForeignSession:
    """A discoverable session in another tool's on-disk store."""

    source: str  # "claude" | "codex"
    path: Path
    mtime: float
    cwd: Optional[str] = None
    title_guess: Optional[str] = None
    turn_count: int = 0
    session_id: Optional[str] = None  # the foreign tool's own id

    @property
    def label(self) -> str:
        title = (self.title_guess or "").strip() or self.path.stem
        return f"[{_SOURCE_LABELS.get(self.source, self.source)}] {title[:_TITLE_MAX]}"


def _read_json_lines(path: Path):
    """Yield parsed JSON objects, silently skipping unparseable lines."""
    try:
        with open(path, "r", encoding="utf-8-sig", errors="replace") as f:
            for line in f:
                line = line.strip()
                if not line:
                    continue
                try:
                    obj = json.loads(line)
                except (json.JSONDecodeError, ValueError):
                    continue
                if isinstance(obj, dict):
                    yield obj
    except OSError:
        return


def _block_text(block: Any) -> str:
    """Plain text of one content block; tool_result, thinking/reasoning and unknown types yield ''."""
    if isinstance(block, str):
        return block
    if not isinstance(block, dict):
        return ""
    btype = block.get("type")
    if btype in ("text", "input_text", "output_text"):
        return text if isinstance(text := block.get("text"), str) else ""
    if btype == "tool_use":  # Claude Code assistant block
        return f"[ran tool: {block.get('name') or 'tool'}]"
    return "[image]" if btype == "image" else ""


def _flatten_blocks(content: Any) -> str:
    """Flatten a message ``content`` (string or block list) to plain text."""
    if isinstance(content, str):
        return content
    if not isinstance(content, list):
        return ""
    return "\n\n".join(p for p in (_block_text(b).strip() for b in content) if p)


def _merge_turns(raw_turns: List[Tuple[str, str]]) -> List[Dict[str, str]]:
    """Merge consecutive same-role turns; guarantee strict alternation.

    A leading assistant turn (session began before the log window) gets a minimal user stub so the
    first message is always ``user``; this is the only place a stub is ever inserted.
    """
    merged: List[Dict[str, str]] = []
    for role, text in raw_turns:
        if not (text := text.strip()):
            continue
        if merged and merged[-1]["role"] == role:
            merged[-1]["content"] += "\n\n" + text
        else:
            merged.append({"role": role, "content": text})
    if merged and merged[0]["role"] == "assistant":
        merged.insert(0, {"role": "user", "content": "(imported conversation begins with an assistant reply)"})
    return merged


def _message_turn(message: Any) -> Optional[Tuple[str, str]]:
    """Normalize one message dict into a ``(role, text)`` turn, or None when it is not importable."""
    role = message.get("role") if isinstance(message, dict) else None
    if role not in ("user", "assistant"):
        return None
    text = _flatten_blocks(message.get("content"))
    return None if not text or (role == "user" and _WRAPPER_TAG_RE.match(text.lstrip())) else (role, text)


def _first_user_line(turns: List[Tuple[str, str]]) -> Optional[str]:
    for role, text in turns:
        if role == "user" and (line := text.strip().partition("\n")[0].strip()):
            return line[:_TITLE_MAX * 2]
    return None


def _parsed(turns: List[Tuple[str, str]], cwd: Optional[str], session_id: Optional[str],
            title: Optional[str] = None) -> Dict[str, Any]:
    return {"turns": _merge_turns(turns), "cwd": cwd, "title_guess": title or _first_user_line(turns),
            "session_id": session_id}


def parse_claude_session(path: Path) -> Dict[str, Any]:
    """Parse one Claude Code session JSONL into normalized turns + meta."""
    turns: List[Tuple[str, str]] = []
    cwd = summary = session_id = None
    for obj in _read_json_lines(path):
        otype = obj.get("type")
        if otype == "summary":
            if isinstance(s := obj.get("summary"), str) and s.strip():
                summary = s.strip()
        elif otype in ("user", "assistant") and not (obj.get("isSidechain") or obj.get("isMeta")):
            if cwd is None and isinstance(obj.get("cwd"), str):
                cwd = obj["cwd"]
            if session_id is None and isinstance(obj.get("sessionId"), str):
                session_id = obj["sessionId"]
            if turn := _message_turn(obj.get("message")):
                turns.append(turn)
    return _parsed(turns, cwd, session_id, summary)


def parse_codex_session(path: Path) -> Dict[str, Any]:
    """Parse one Codex CLI rollout JSONL into normalized turns + meta."""
    turns: List[Tuple[str, str]] = []
    cwd = session_id = None
    for obj in _read_json_lines(path):
        otype, payload = obj.get("type"), obj.get("payload")
        if not isinstance(payload, dict):
            continue
        if otype == "session_meta":
            if isinstance(payload.get("cwd"), str):
                cwd = payload["cwd"]
            if isinstance(sid := payload.get("session_id") or payload.get("id"), str):
                session_id = sid
        elif otype == "response_item":
            ptype = payload.get("type")
            if ptype == "message" and (turn := _message_turn(payload)):  # developer/system payloads skipped
                turns.append(turn)
            elif ptype in ("custom_tool_call", "function_call", "local_shell_call"):
                # Assistant activity; merged into neighbours later. Tool outputs / reasoning skipped.
                name = payload.get("name") or payload.get("tool") or "tool"
                turns.append(("assistant", f"[ran tool: {name}]"))
    return _parsed(turns, cwd, session_id)


# source -> (default root under ~, env override var, subdir under the env root, glob pattern,
#            recursive, parser)
_SOURCES = {
    "claude": ((".claude", "projects"), "CLAUDE_CONFIG_DIR", "projects", "*/*.jsonl", False,
               parse_claude_session),
    "codex": ((".codex", "sessions"), "CODEX_HOME", "sessions", "rollout-*.jsonl", True,
              parse_codex_session),
}


def _parser(source: str):
    return _SOURCES[source][5]


def _default_root(source: str) -> Path:
    """Default session store for *source*, honoring the tool's own relocation env var.

    Claude Code moves its whole config dir with ``CLAUDE_CONFIG_DIR``; Codex CLI with
    ``CODEX_HOME``. A blank/whitespace value is treated as unset (an empty override must not
    resolve to a relative ``"projects"`` under the CWD). Ported from cline/cline#13827."""
    default_parts, env_var, env_subdir, *_ = _SOURCES[source]
    override = os.environ.get(env_var, "").strip()
    if override:
        return Path(override).expanduser() / env_subdir
    return Path.home().joinpath(*default_parts)


def _walk(source: str, root: Optional[Path] = None) -> List[Tuple[Path, os.stat_result]]:
    """Regular log files of *source* under *root* (default: the tool's env-aware store, see
    ``_default_root``) as ``(path, stat)``, newest first. Symlinks escaping the root and
    unreadable/rotated entries are skipped, so one bad file never hides the rest. Shared by the
    CLI picker and the desktop browser."""
    pattern, recursive = _SOURCES[source][3], _SOURCES[source][4]
    root = (Path(root) if root else _default_root(source)).resolve()
    found: List[Tuple[Path, os.stat_result]] = []
    for path in (root.rglob(pattern) if recursive else root.glob(pattern)) if root.is_dir() else ():
        try:
            resolved = path.resolve()
            st = resolved.stat()
        except OSError:
            continue
        if resolved.is_relative_to(root) and S_ISREG(st.st_mode):
            found.append((resolved, st))
    found.sort(key=lambda item: item[1].st_mtime, reverse=True)
    return found


def _list_sessions(source: str, root: Optional[Path]) -> List[ForeignSession]:
    parse = _parser(source)
    results: List[ForeignSession] = []
    for path, st in _walk(source, root):
        parsed = parse(path)
        if parsed["turns"]:
            results.append(ForeignSession(source, path, st.st_mtime, parsed["cwd"], parsed["title_guess"],
                                          len(parsed["turns"]), parsed["session_id"]))
    return results


def import_foreign_session(source: str, path, db=None) -> str:
    """Import one foreign session into the Hermes SessionDB; returns the new Hermes session id.

    Raises ``ValueError`` on unknown source or a session with no usable conversation turns."""
    source = (source or "").strip().lower().lstrip("@")
    if source not in _SOURCE_LABELS:
        raise ValueError(f"Unknown foreign session source: {source!r}")
    path = Path(path).expanduser()
    if not path.is_file():
        raise ValueError(f"Session file not found: {path}")
    parsed = _parser(source)(path)
    turns = parsed["turns"]
    if not turns:
        raise ValueError(f"No user/assistant conversation turns found in {path}")
    first_user = _first_user_line([(t["role"], t["content"]) for t in turns]) or path.stem
    if len(first_user) > _TITLE_MAX:
        first_user = first_user[: _TITLE_MAX - 1] + "…"
    tool = _SOURCE_DB_NAMES[source]
    owns_db = db is None
    if owns_db:
        from hermes_state_registry import acquire
        db = acquire()  # the CLI resume that follows acquires this same handle
    try:
        session_id = new_session_id()
        origin = {"imported_from": {"tool": tool, "path": str(path), "foreign_session_id": parsed.get("session_id")}}
        db.create_session(session_id, source=tool, cwd=parsed.get("cwd"), origin_json=json.dumps(origin))
        for turn in turns:
            db.append_message(session_id, turn["role"], turn["content"])
        with contextlib.suppress(Exception):  # title is cosmetic; the import itself succeeded
            db.set_session_title(session_id, f"Imported from {_SOURCE_LABELS[source]}: {first_user}")
        return session_id
    finally:
        if owns_db:
            with contextlib.suppress(Exception):
                db.close()


def gather_foreign_sessions(source: Optional[str] = None, *, claude_root: Optional[Path] = None,
                            codex_root: Optional[Path] = None, limit: int = 25) -> List[ForeignSession]:
    """List foreign sessions across sources, newest first."""
    sessions = [s for name, root in (("claude", claude_root), ("codex", codex_root)) if source in (None, name)
                for s in _list_sessions(name, root)]
    sessions.sort(key=lambda s: s.mtime, reverse=True)
    return sessions[:limit] if limit else sessions


def pick_foreign_session(source: Optional[str] = None, *, limit: int = 25) -> Optional[ForeignSession]:
    """Interactive numbered picker. Returns None when nothing was chosen."""
    sessions = gather_foreign_sessions(source, limit=limit)
    if not sessions:
        where = _SOURCE_LABELS.get(source or "", "Claude Code or Codex CLI")
        print(f"No {where} sessions found on this machine.")
        return None
    print("Foreign sessions (newest first):")
    for i, s in enumerate(sessions, 1):
        ws = f"  ({os.path.basename(s.cwd.rstrip('/')) or s.cwd})" if s.cwd else ""
        print(f"  {i:>2}. {datetime.fromtimestamp(s.mtime):%Y-%m-%d %H:%M}  {s.label}{ws}  [{s.turn_count} turns]")
    if not sys.stdin.isatty():
        print("Non-interactive terminal — pass the file path directly:\n"
              "  hermes sessions import --from claude|codex <path>")
        return None
    try:
        raw = input(f"Import which session? [1-{len(sessions)}, empty to cancel] ").strip()
        idx = int(raw) if raw else None
    except (EOFError, KeyboardInterrupt):
        return None
    except ValueError:
        print(f"Not a number: {raw}")
        return None
    if idx is not None and 1 <= idx <= len(sessions):
        return sessions[idx - 1]
    if idx is not None:
        print(f"Out of range: {idx}")
    return None


def run_sessions_import(args, db=None) -> Optional[str]:
    """`hermes sessions import` entry point. Returns new session id or None."""
    source = getattr(args, "from_source", None)
    path = getattr(args, "path", None)
    if path:
        # A missing file is reported as such, not as the misleading "cannot infer source".
        if not Path(path).exists():
            print(f"Error: file not found: {path}")
            return None
        if not source:  # guess from the path shape; a codex match wins over a claude match
            p = str(path)
            if "/.claude/" in p or p.endswith(".jsonl") and "claude" in p:
                source = "claude"
            if "/.codex/" in p or Path(p).name.startswith("rollout-"):
                source = "codex"
        if not source:
            print("Cannot infer source from path; pass --from claude|codex.")
            return None
        chosen_path = Path(path)
    else:
        if (picked := pick_foreign_session(source)) is None:
            return None
        source, chosen_path = picked.source, picked.path
    try:
        session_id = import_foreign_session(source, chosen_path, db=db)
    except ValueError as e:
        print(f"Error: {e}")
        return None
    print(f"✓ Imported {_SOURCE_LABELS.get(source, source)} session as {session_id}")
    print(f"  Continue it with:  hermes --resume {session_id}")
    return session_id