import json
import os
import re
import shutil
import subprocess
import tempfile
from abc import ABC, abstractmethod
from collections.abc import Generator
from dataclasses import dataclass
from pathlib import Path


@dataclass
class KernelRequest:
    skill_path: str  # path to SKILL.md
    prompt: str  # user's kernel generation prompt


@dataclass
class KernelResponse:
    streaming_output: str = ""  # intermediate output (from assistant events)
    final_output: str = ""  # final result (from result event only)
    log: str = ""  # full log of all events
    file_tree: str = ""  # text-based tree of generated files
    files: dict[str, str] | None = None  # relative_path -> content
    error: str | None = None  # error message if failed


class Executor(ABC):
    @abstractmethod
    def execute(self, request: KernelRequest) -> KernelResponse:
        ...

    @abstractmethod
    def stream(self, request: KernelRequest) -> Generator[KernelResponse, None, None]:
        ...


def _scan_generated_files(tmpdir: str) -> tuple[str, dict[str, str]]:
    """Walk tmpdir for files Claude created, skipping .claude/ scaffolding.

    Returns (tree_string, {relative_path: file_content}).
    """
    root = Path(tmpdir)
    files: dict[str, str] = {}
    for path in sorted(root.rglob("*")):
        if not path.is_file():
            continue
        rel = path.relative_to(root)
        # Skip our scaffolding
        if rel.parts[0] == ".claude":
            continue
        try:
            files[str(rel)] = path.read_text()
        except (OSError, UnicodeDecodeError):
            files[str(rel)] = "<binary or unreadable>"

    if not files:
        return "(no files generated)", {}

    # Build a simple text tree
    lines = []
    names = list(files.keys())
    for i, name in enumerate(names):
        connector = "└── " if i == len(names) - 1 else "├── "
        lines.append(f"{connector}{name}")
    return "\n".join(lines), files


def _parse_frontmatter(content: str) -> dict[str, str]:
    """Extract YAML frontmatter fields from a SKILL.md file."""
    match = re.match(r"^---\s*\n(.*?)\n---", content, re.DOTALL)
    if not match:
        return {}
    fields = {}
    for line in match.group(1).splitlines():
        if ":" in line:
            key, _, value = line.partition(":")
            fields[key.strip()] = value.strip().strip('"')
    return fields


class LocalCLIExecutor(Executor):
    """Runs `claude` CLI with native skill discovery via a temp directory.

    Copies the SKILL.md and all files listed in manifest.txt into a
    temporary .claude/skills/<name>/ directory, then runs `claude -p`
    from there so the skill is discovered natively without touching
    the real project's .claude/ directory.
    """

    def __init__(self, project_dir: str | None = None):
        self.project_dir = project_dir or os.getcwd()
        self._prev_tmpdir: str | None = None

    def _load_skill(self, skill_path: str) -> tuple[str | None, Path, str, dict[str, str]]:
        """Read skill file and parse its frontmatter.

        Returns (error_or_none, skill_dir, file_content, frontmatter_dict).
        """
        src = Path(skill_path)
        if not src.is_absolute():
            src = Path(self.project_dir) / src

        if not src.exists():
            return f"SKILL.md not found at: {src}", Path(), "", {}

        try:
            content = src.read_text()
        except OSError as e:
            return f"Failed to read SKILL.md: {e}", Path(), "", {}

        frontmatter = _parse_frontmatter(content)
        return None, src.parent, content, frontmatter

    def _install_skill_files(self, skill_src_dir: Path, dest_dir: Path) -> str | None:
        """Copy all files listed in manifest.txt into the dest skill directory.

        If no manifest.txt exists, only the SKILL.md (already written by caller)
        is present. Returns an error string on failure, None on success.
        """
        manifest = skill_src_dir / "manifest.txt"
        if not manifest.exists():
            return None

        try:
            lines = manifest.read_text().splitlines()
        except OSError as e:
            return f"Failed to read manifest.txt: {e}"

        for line in lines:
            entry = line.strip()
            if not entry or entry.startswith("#"):
                continue
            if entry == "SKILL.md":
                continue

            src_file = skill_src_dir / entry
            dest_file = dest_dir / entry
            if not src_file.exists():
                continue

            try:
                dest_file.parent.mkdir(parents=True, exist_ok=True)
                shutil.copy2(src_file, dest_file)
            except OSError as e:
                return f"Failed to copy {entry}: {e}"

        return None

    def _prepare(self, request: KernelRequest) -> tuple[str | None, str, dict[str, str], str]:
        """Set up temp dir with skill files. Returns (error, skill_name, frontmatter, tmpdir_path)."""
        # Clean up previous run's temp dir
        if self._prev_tmpdir:
            shutil.rmtree(self._prev_tmpdir, ignore_errors=True)
            self._prev_tmpdir = None

        err, skill_src_dir, skill_content, frontmatter = self._load_skill(request.skill_path)
        if err:
            return err, "", {}, ""

        skill_name = frontmatter.get("name", "skill")
        tmpdir = tempfile.mkdtemp()

        skill_dest = Path(tmpdir) / ".claude" / "skills" / skill_name
        skill_dest.mkdir(parents=True)
        (skill_dest / "SKILL.md").write_text(skill_content)

        err = self._install_skill_files(skill_src_dir, skill_dest)
        if err:
            shutil.rmtree(tmpdir, ignore_errors=True)
            return err, "", {}, ""

        return None, skill_name, frontmatter, tmpdir

    def _build_cmd(self, request: KernelRequest, frontmatter: dict[str, str], streaming: bool = False) -> list[str]:
        cmd = ["claude"]
        if streaming:
            cmd.extend(["--output-format", "stream-json", "--verbose"])
        allowed_tools = frontmatter.get("allowed-tools")
        if allowed_tools:
            tools = [t.strip() for t in allowed_tools.split(",")]
            cmd.extend(["--allowedTools"] + tools)
        # -p and prompt go last so flags aren't misinterpreted
        cmd.extend(["-p", request.prompt])
        return cmd

    def execute(self, request: KernelRequest) -> KernelResponse:
        err, skill_name, frontmatter, tmpdir = self._prepare(request)
        if err:
            return KernelResponse(error=err)

        cmd = self._build_cmd(request, frontmatter)

        try:
            result = subprocess.run(
                cmd,
                capture_output=True,
                text=True,
                timeout=120,
                cwd=tmpdir,
            )
        except FileNotFoundError:
            return KernelResponse(
                error="'claude' CLI not found. Make sure it is installed and on your PATH.",
            )
        except subprocess.TimeoutExpired:
            return KernelResponse(
                error="Claude CLI timed out after 120 seconds.",
            )
        finally:
            shutil.rmtree(tmpdir, ignore_errors=True)

        if result.returncode != 0:
            return KernelResponse(
                error=f"Claude CLI exited with code {result.returncode}: {result.stderr}",
            )

        return KernelResponse(final_output=result.stdout)

    def stream(self, request: KernelRequest) -> Generator[KernelResponse, None, None]:
        err, skill_name, frontmatter, tmpdir = self._prepare(request)
        if err:
            yield KernelResponse(error=err)
            return

        cmd = self._build_cmd(request, frontmatter, streaming=True)

        try:
            proc = subprocess.Popen(
                cmd,
                stdout=subprocess.PIPE,
                stderr=subprocess.PIPE,
                text=True,
                bufsize=1,  # line-buffered
                cwd=tmpdir,
            )
        except FileNotFoundError:
            shutil.rmtree(tmpdir, ignore_errors=True)
            yield KernelResponse(
                error="'claude' CLI not found. Make sure it is installed and on your PATH.",
            )
            return

        streaming = ""
        final = ""
        log_lines: list[str] = []
        try:
            # Use readline() instead of iterating proc.stdout to avoid
            # Python's internal read-ahead buffer which blocks streaming.
            while True:
                line = proc.stdout.readline()
                if not line and proc.poll() is not None:
                    break
                line = line.strip()
                if not line:
                    continue
                try:
                    event = json.loads(line)
                except json.JSONDecodeError:
                    continue

                etype = event.get("type")

                # Log system events (hooks, init)
                if etype == "system":
                    subtype = event.get("subtype", "")
                    if subtype == "init":
                        log_lines.append("[init] Session started")
                    elif subtype == "hook_started":
                        log_lines.append(f"[hook] {event.get('hook_name', '?')} started")
                    elif subtype == "hook_response":
                        outcome = event.get("outcome", "?")
                        log_lines.append(f"[hook] {event.get('hook_name', '?')} → {outcome}")
                    else:
                        log_lines.append(f"[system] {subtype}")
                    yield KernelResponse(
                        streaming_output=streaming,
                        final_output=final,
                        log="\n".join(log_lines),
                    )

                # Assistant message chunks — intermediate output
                elif etype == "assistant":
                    content = event.get("message", {}).get("content", [])
                    text = "".join(
                        block["text"]
                        for block in content
                        if block.get("type") == "text"
                    )
                    if text:
                        streaming += text + "\n"
                        log_lines.append(f"[assistant] Received {len(text)} chars")
                        yield KernelResponse(
                            streaming_output=streaming,
                            final_output=final,
                            log="\n".join(log_lines),
                        )

                # Final result — definitive output
                elif etype == "result":
                    if event.get("is_error"):
                        log_lines.append(f"[error] {event.get('result', 'unknown error')}")
                    else:
                        result_text = event.get("result", "")
                        if result_text:
                            final = result_text
                        duration = event.get("duration_ms", 0)
                        cost = event.get("total_cost_usd", 0)
                        log_lines.append(f"[done] {duration}ms, ${cost:.4f}")
                    yield KernelResponse(
                        streaming_output=streaming,
                        final_output=final,
                        log="\n".join(log_lines),
                    )

            proc.wait()
            if proc.returncode != 0:
                stderr = proc.stderr.read()
                log_lines.append(f"[error] exit code {proc.returncode}")
                yield KernelResponse(
                    streaming_output=streaming,
                    final_output=final,
                    log="\n".join(log_lines),
                    error=f"Claude CLI exited with code {proc.returncode}: {stderr}",
                )

            # Scan for generated files and yield final response
            file_tree, files = _scan_generated_files(tmpdir)
            if files:
                log_lines.append(f"[files] {len(files)} file(s) generated")
            yield KernelResponse(
                streaming_output=streaming,
                final_output=final,
                log="\n".join(log_lines),
                file_tree=file_tree,
                files=files,
            )
            # Keep tmpdir alive so the UI can reference files
            self._prev_tmpdir = tmpdir
        finally:
            if proc.poll() is None:
                proc.kill()