"""ROS 2 request -> RAG-grounded package, validated against the indexed interface definitions.

Two backends generate the files:
- "opencode" (default): OpenCode runs headless in a throwaway workspace and writes the package
  itself; the RAG context is attached to its message. Repairs continue the same OpenCode session.
- "direct": one chat call returns the files as fenced blocks. Used when OpenCode is not
  installed, and in tests.
"""

from __future__ import annotations

import logging
import re
from dataclasses import dataclass, field
from typing import Protocol

from rag.chunking import interface_kind
from rag.store import Hit, RagStore, format_context

from .config import Settings
from .llm import LLM, LLMError, Message
from .opencode_runner import OpenCodeError, OpenCodeWorkspace
from .ros_check import CodeValidation, load_interfaces, validate_package
from .routing import is_free

log = logging.getLogger("rosdiff.codegen")

DISTROS = ("humble", "jazzy")
LANGUAGES = ("python", "cpp")

TASK_TEMPLATE = """Create a complete, buildable ROS 2 {distro} package in {language_name} for this request:

{request}

Requirements:
- Package name: {package_name}. Put the package in the directory ./{package_name}/.
- {layout}
- Use only message/service types whose definitions appear in the ROS 2 CONTEXT (they are verified to exist in
  {distro}). Declare every package you use in package.xml.
- Follow the APIs shown in the ROS 2 CONTEXT (rclpy / rclcpp, launch). Include a launch file in
  ./{package_name}/launch/ that starts the node(s) with sensible parameters.
- Include short comments where behaviour is not obvious. No placeholders or TODOs: the code must run as is.
"""

LAYOUT = {
    "python": "ament_python layout: package.xml, setup.py, setup.cfg, resource/<name>, <name>/__init__.py, "
    "<name>/<node>.py with a main() registered under console_scripts, and the launch file installed via data_files.",
    "cpp": "ament_cmake layout: package.xml, CMakeLists.txt (find_package, add_executable, "
    "ament_target_dependencies, install targets and launch dir, ament_package()), src/<node>.cpp.",
}

DIRECT_FORMAT = """Output every file of the package in this exact format and nothing else between files:

FILE: <relative/path>
```<language>
<complete file content>
```
"""


class CodeBackend(Protocol):
    name: str

    def generate(self, task: str, context: str) -> tuple[dict[str, str], str]: ...

    def repair(self, feedback: str, context: str) -> tuple[dict[str, str], str]: ...


@dataclass
class CodeAttempt:
    files: dict[str, str]
    validation: dict
    transcript: str
    model: str = ""
    usage: dict = field(default_factory=dict)


@dataclass
class CodeResult:
    valid: bool
    files: dict[str, str]
    validation: CodeValidation
    attempts: list[CodeAttempt] = field(default_factory=list)
    sources: list[str] = field(default_factory=list)
    backend: str = ""
    model: str = ""


# --------------------------------------------------------------------------- retrieval


def mentioned_interfaces(request: str, interfaces: dict[str, str]) -> list[str]:
    """Interfaces named in the request, e.g. 'LaserScan' or 'sensor_msgs/LaserScan'."""
    words = set(re.findall(r"[A-Za-z_]+(?:/[A-Za-z_]+)*", request))
    found = []
    for name in interfaces:
        pkg, _, base = name.split("/")
        if base in words or f"{pkg}/{base}" in words or name in words:
            found.append(name)
    return sorted(found)


def nested_types(definition: str, own_package: str, interfaces: dict[str, str]) -> list[str]:
    """Field types used inside a message definition, resolved to full interface names."""
    out = []
    for line in definition.splitlines():
        line = line.split("#", 1)[0].strip()
        if not line or "=" in line.split()[0]:
            continue
        type_name = re.sub(r"\[.*\]$", "", line.split()[0])
        if "/" in type_name:
            pkg, base = type_name.split("/")[0], type_name.split("/")[-1]
        else:
            pkg, base = own_package, type_name
        full = f"{pkg}/msg/{base}"
        if full in interfaces:
            out.append(full)
    return out


def retrieve(store: RagStore, request: str, distro: str, language: str, interfaces: dict[str, str]) -> list[Hit]:
    hits: list[Hit] = []
    # 1. Exact definitions of interfaces the request names, plus the types they contain (one level).
    named = mentioned_interfaces(request, interfaces)
    expanded = list(named)
    for name in named:
        for sub in nested_types(interfaces[name], name.split("/")[0], interfaces):
            if sub not in expanded:
                expanded.append(sub)
    for name in expanded[:12]:
        kind = interface_kind(name)
        hits.append(
            Hit(
                f"[ROS 2 {distro} {kind} {name}]\n{interfaces[name].strip()}",
                f"interface:{distro}:{name}",
                0.0,
                {"kind": "interface"},
            )
        )
    # 2. Other interfaces that look relevant.
    hits += store.query("ros2", request, k=4, where={"$and": [{"kind": "interface"}, {"distro": distro}]})
    # 3. Tutorials and how-tos for the right distro and language.
    lang = "Python rclpy" if language == "python" else "C++ rclcpp"
    hits += store.query("ros2", f"{lang} {request}", k=6, where={"$and": [{"kind": "doc"}, {"distro": distro}]})
    seen, unique = set(), []
    for h in hits:
        if h.text not in seen:
            seen.add(h.text)
            unique.append(h)
    return unique


# --------------------------------------------------------------------------- backends


_FILE_BLOCK = re.compile(r"^FILE:\s*(?P<path>\S+)\s*\n```[\w+-]*\n(?P<body>.*?)^```", re.MULTILINE | re.DOTALL)


def parse_file_blocks(text: str) -> dict[str, str]:
    return {m.group("path").strip("`'\""): m.group("body") for m in _FILE_BLOCK.finditer(text)}


class DirectBackend:
    name = "direct"

    def __init__(self, llm: LLM):
        self.llm = llm
        self.messages: list[Message] = []
        self.model: str | None = None  # set per attempt by the router
        self.last_usage: dict = {}

    def _call(self) -> tuple[dict[str, str], str]:
        completion = (
            self.llm.complete(self.messages, model=self.model) if self.model else self.llm.complete(self.messages)
        )
        self.last_usage = dict(completion.usage or {})
        self.messages.append(Message("assistant", completion.text))
        return parse_file_blocks(completion.text), completion.text

    def generate(self, task: str, context: str) -> tuple[dict[str, str], str]:
        self.messages = [
            Message(
                "system", "You are an expert ROS 2 developer who writes correct, buildable packages.\n" + DIRECT_FORMAT
            ),
            Message("user", f"ROS 2 CONTEXT:\n{context}\n\nTASK:\n{task}"),
        ]
        return self._call()

    def repair(self, feedback: str, context: str) -> tuple[dict[str, str], str]:
        self.messages.append(
            Message(
                "user",
                f"{feedback}\n\nFix these problems and output ALL files of the package again in the same format.",
            )
        )
        return self._call()


class OpenCodeBackend:
    name = "opencode"

    def __init__(self, workspace: OpenCodeWorkspace):
        self.workspace = workspace
        self.model: str | None = None  # set per attempt by the router
        self.last_usage: dict = {}

    def _result(self, run) -> tuple[dict[str, str], str]:
        self.last_usage = run.usage()
        if run.error:
            raise LLMError(f"OpenCode: {run.error}")
        texts = [e.get("part", {}).get("text", "") for e in run.events if e.get("type") == "text"]
        return self.workspace.collect(), "\n".join(t for t in texts if t)

    def generate(self, task: str, context: str) -> tuple[dict[str, str], str]:
        message = (
            task + "\nThe attached file contains the ROS 2 CONTEXT. Write the files directly into the "
            "current directory using your edit tools; do not run shell commands."
        )
        return self._run(message, f"# ROS 2 CONTEXT\n\n{context}\n")

    def repair(self, feedback: str, context: str) -> tuple[dict[str, str], str]:
        return self._run(f"{feedback}\n\nFix these problems by editing the files.", f"# ROS 2 CONTEXT\n\n{context}\n")

    def _run(self, message: str, context: str) -> tuple[dict[str, str], str]:
        # free debugging models live under OpenCode's own Zen provider, paid ones under "llm" (OpenRouter)
        if is_free(self.model):
            provider, _, model = self.model.partition("/")
            return self._result(self.workspace.run(message, context, model=model, provider=provider))
        return self._result(self.workspace.run(message, context, model=self.model))


# --------------------------------------------------------------------------- pipeline


def default_package_name(request: str) -> str:
    words = [w.lower() for w in re.findall(r"[A-Za-z]+", request) if len(w) > 2][:3]
    return "_".join(words) or "generated_pkg"


def generate_code(
    request: str,
    distro: str,
    language: str,
    backend: CodeBackend,
    store: RagStore,
    settings: Settings,
    package_name: str | None = None,
    max_attempts: int | None = None,
    plan=None,
) -> CodeResult:
    """`plan` (api.routing.Plan) picks the model per attempt: the planned tier first, one tier up per repair."""
    from .routing import candidates_for_attempt

    if distro not in DISTROS:
        raise ValueError(f"distro must be one of {DISTROS}")
    if language not in LANGUAGES:
        raise ValueError(f"language must be one of {LANGUAGES}")
    catalogue = load_interfaces(str(settings.interfaces_file))
    interfaces = catalogue.get(distro, {})
    hits = retrieve(store, request, distro, language, interfaces)
    context = format_context(hits, max_chars=16000)
    package_name = package_name or default_package_name(request)
    task = TASK_TEMPLATE.format(
        distro=distro,
        language_name="Python (rclpy)" if language == "python" else "C++ (rclcpp)",
        request=request.strip(),
        package_name=package_name,
        layout=LAYOUT[language],
    )

    attempts: list[CodeAttempt] = []
    files: dict[str, str] = {}
    validation = CodeValidation(False, ["no attempt made"])
    for i in range(max(1, max_attempts or settings.code_max_attempts)):
        candidates = [m.id for m in candidates_for_attempt(plan, i)] if plan is not None else [None]
        for n, model in enumerate(candidates):
            if model is not None:
                backend.model = model
            try:
                files, transcript = (
                    backend.generate(task, context) if i == 0 else backend.repair(validation.feedback(), context)
                )
                break
            except (OpenCodeError, LLMError) as e:
                if n == len(candidates) - 1:
                    raise LLMError(str(e)) from e
                log.info("model %s failed (%s); falling back to %s", model, e, candidates[n + 1])
        validation = validate_package(files, distro, catalogue)
        used = getattr(backend, "model", None) or getattr(getattr(backend, "llm", None), "model", "") or ""
        attempts.append(
            CodeAttempt(dict(files), validation.to_dict(), transcript, used, dict(getattr(backend, "last_usage", {})))
        )
        if validation.valid:
            break
    model = (attempts[-1].model if attempts else "") or settings.code_llm_model
    return CodeResult(
        valid=validation.valid,
        files=files,
        validation=validation,
        attempts=attempts,
        sources=[h.source for h in hits],
        backend=backend.name,
        model=model,
    )