"""Executor contract (docs/executor-contract.md).

agentd is not resident: a run outlives the process that started it, so `start` returns a JSON-serialisable
handle that is stored in the state file, and `poll`/`collect`/`kill` work from that handle alone."""
import re
from dataclasses import dataclass, field
from typing import List, Optional


@dataclass
class Run:
    run_id: str
    repo: str
    prompt: str
    model: Optional[str] = None
    effort: Optional[str] = None
    tier: Optional[str] = None
    thread_id: Optional[str] = None   # set => resume this thread
    script: Optional[str] = None      # shell executor


@dataclass
class ExecResult:
    last_message: str
    exit_code: Optional[int]
    thread_id: Optional[str]
    log_paths: List[str] = field(default_factory=list)
    tail: str = ""                    # last frame: stderr tail / last event, for failure notes


class Executor:
    """Abstract adapter. `resume` says whether the executor can continue a thread."""
    resume = False

    def __init__(self, name, cfg, terminal, tcfg, transport):
        self.name, self.cfg, self.terminal, self.tcfg, self.transport = name, cfg, terminal, tcfg, transport

    def start(self, run):            # -> handle (dict)
        raise NotImplementedError

    def poll(self, handle):          # -> "running" | "finished"
        raise NotImplementedError

    def collect(self, handle):       # -> ExecResult
        raise NotImplementedError

    def kill(self, handle):
        raise NotImplementedError


def fill(template, params):
    """Replace {name} placeholders that exist in params; leave anything else untouched."""
    return re.sub(r"\{(\w+)\}", lambda m: str(params[m.group(1)]) if m.group(1) in params else m.group(0), template)


class RunnerExecutor(Executor):
    """Common shape for CLI executors: write prompt.md + a runner script into a run directory on the terminal,
    launch it detached through the transport, and treat `exit.txt` as the completion marker.
    Subclasses define `stdout_name` and `collect`."""
    stdout_name = "stdout.txt"

    @property
    def resume(self):
        return isinstance(self.cfg.get("resume"), str) and bool(self.cfg["resume"])

    def run_root(self):
        return self.tcfg.get("run_root") or self.transport.default_run_root()

    def params(self, run, run_dir):
        tier = fill(self.cfg.get("tier_arg", ""), {"tier": run.tier}) if run.tier else ""
        return {"repo": run.repo, "model": run.model or "", "effort": run.effort or "", "tier": tier,
                "out": self.transport.join(run_dir, "last.md"), "thread": run.thread_id or "",
                "perm": self.cfg.get("permission_mode", "default"), "run_dir": run_dir,
                "script": run.script or self.cfg.get("script", "")}

    def command(self, run, run_dir):
        template = self.cfg["resume"] if run.thread_id and self.resume else self.cfg["run"]
        cmd = " ".join(fill(template, self.params(run, run_dir)).split())
        program, _, rest = cmd.partition(" ")
        binary = self.tcfg.get("bins", {}).get(program)
        if binary:
            program = self.transport.quote(binary)
        if self.transport.os == "windows" and (binary or program.startswith("'")):
            program = "& " + program
        return (program + " " + rest).strip()

    def start(self, run):
        t = self.transport
        run_dir = t.join(self.run_root(), run.run_id)
        t.mkdir(run_dir, clean=True)
        t.write_text(t.join(run_dir, "prompt.md"), run.prompt)
        script_name, script = t.runner(run_dir, run.repo, self.command(run, run_dir), self.stdout_name)
        script_path = t.join(run_dir, script_name)
        t.write_text(script_path, script)
        task = "agentd-" + run.run_id
        t.launch(task, script_path, run_dir)
        return {"run_dir": run_dir, "task": task, "thread_id": run.thread_id}

    def poll(self, handle):
        text = self.transport.read_text(self.transport.join(handle["run_dir"], "exit.txt"))
        return "finished" if text and "exit=" in text else "running"

    def exit_code(self, handle):
        text = self.transport.read_text(self.transport.join(handle["run_dir"], "exit.txt")) or ""
        m = re.search(r"exit=(-?\d+)", text)
        return int(m.group(1)) if m else None

    def kill(self, handle):
        self.transport.kill(handle["task"], handle["run_dir"])

    def logs(self, handle, *names):
        return [self.transport.join(handle["run_dir"], n) for n in names]

    def stderr_tail(self, handle, n=5):
        return self.transport.tail(self.transport.join(handle["run_dir"], "stderr.txt"), n)

    def forget(self, handle):
        try:
            self.transport.forget(handle["task"])
        except Exception:
            pass