# Copyright 2026 The Fuchsia Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

import json
import os
import subprocess
import sys
import time
import xml.etree.ElementTree as ET
from dataclasses import dataclass
from enum import Enum
from pathlib import Path

from build_dir import BuildDir
from utils import run_git, run_jj


class NoFreeWorktreesError(RuntimeError):
    pass


class WorktreeState(Enum):
    FREE = "free"
    LEASED = "leased"


class SyncStatus(Enum):
    SYNCED = "Synced"
    BEHIND = "behind"
    NEW = "new"
    DIVERGED = "behind, new"
    UNKNOWN = "Unknown"


@dataclass
class LeaseInfo:
    worktree_id: str
    pid: int
    timestamp_sec: int
    task_id: str | None = None


class Worktree:
    def __init__(self, name: str, path: Path, main_checkout_dir: Path):
        self.name = name
        self.path = Path(path).resolve()
        self.main_checkout_dir = Path(main_checkout_dir).resolve()
        self.meta_dir = self.path / ".jiri_root"
        self.lease_file = self.meta_dir / "lease.json"

    def is_jj_workspace(self) -> bool:
        # A jj workspace's .jj/repo is a file pointing at the main checkout's
        # repo (in the main checkout itself, it's a directory).
        return (self.path / ".jj" / "repo").is_file()

    def jj_workspace_paths(self) -> list[Path]:
        """Returns the slot's jj workspaces: its root and any jj sub-projects.

        Candidate sub-project paths come from the main checkout's latest jiri
        snapshot, so this doesn't have to walk the tree.
        """
        candidates = [self.path]
        snapshot = (
            self.main_checkout_dir / ".jiri_root" / "update_history" / "latest"
        )
        try:
            for project in ET.parse(snapshot).getroot().iter("project"):
                rel_path = project.get("path")
                if not rel_path:
                    continue
                if os.path.isabs(rel_path):
                    rel_path = os.path.relpath(rel_path, self.main_checkout_dir)
                candidates.append(self.path / rel_path)
        except (OSError, ET.ParseError) as e:
            print(
                f"Warning: failed to read {snapshot}; only checking the root for jj workspaces: {e}",
                file=sys.stderr,
            )
        return [
            p
            for p in dict.fromkeys(c.resolve() for c in candidates)
            if (p / ".jj" / "repo").is_file()
        ]

    def rename_jj_workspaces(self, name: str) -> None:
        """Renames the slot's jj workspaces to name, warning on failure."""
        # Renaming a workspace to its current name is a no-op in jj.
        for ws in self.jj_workspace_paths():
            try:
                run_jj(
                    ws,
                    ["workspace", "rename", name],
                    quiet=True,
                    check=True,
                    capture_output=True,
                    text=True,
                )
            except subprocess.CalledProcessError as e:
                print(
                    f"Warning: failed to rename jj workspace '{ws}' to '{name}': {e.stderr or e}",
                    file=sys.stderr,
                )

    def get_state(self) -> WorktreeState:
        if self.lease_file.exists():
            return WorktreeState.LEASED
        return WorktreeState.FREE

    def get_lease_info(self) -> LeaseInfo | None:
        if not self.lease_file.exists():
            return None
        try:
            content = json.loads(self.lease_file.read_text())
            return LeaseInfo(
                worktree_id=content.get("worktree_id", self.name),
                pid=content.get("pid", 0),
                timestamp_sec=content.get("timestamp_sec", 0),
                task_id=content.get("task_id"),
            )
        except Exception:
            return None

    def selected_build_dir(self) -> Path:
        fx_build_dir_file = self.path / ".fx-build-dir"
        if not fx_build_dir_file.exists():
            raise FileNotFoundError(
                f".fx-build-dir does not exist in {self.path}"
            )
        build_dir_rel = fx_build_dir_file.read_text().strip()
        if not build_dir_rel:
            raise ValueError(f".fx-build-dir is empty in {self.path}")
        return (self.path / build_dir_rel).resolve()

    def build_dirs(self) -> list[BuildDir]:
        dirs = set()
        fx_build_dir_file = self.path / ".fx-build-dir"
        if fx_build_dir_file.exists():
            build_dir_rel = fx_build_dir_file.read_text().strip()
            if build_dir_rel:
                try:
                    dirs.add((self.path / build_dir_rel).resolve())
                except OSError:
                    pass
        else:
            try:
                dirs.add((self.path / "out" / "default").resolve())
            except OSError:
                pass

        out_dir = self.path / "out"
        if out_dir.exists():
            for child in out_dir.iterdir():
                if child.is_dir():
                    if (child / "args.gn").exists() or (
                        child / "build.ninja"
                    ).exists():
                        try:
                            dirs.add(child.resolve())
                        except OSError:
                            pass

        return [
            BuildDir(d)
            for d in sorted(dirs)
            if d.exists() and d.is_dir() and d.name != "default"
        ]

    def is_built_recently(
        self, max_age_days: int = 7, now: float | None = None
    ) -> bool:
        max_age_sec = max_age_days * 24 * 60 * 60
        for b_dir in self.build_dirs():
            age = b_dir.get_build_time_ago_sec(now=now)
            if age is not None and age <= max_age_sec:
                return True
        return False

    def get_sync_status(self) -> tuple[SyncStatus, int, int]:
        try:
            main_head = run_git(
                self.main_checkout_dir,
                ["rev-parse", "HEAD"],
                quiet=True,
                check=True,
                capture_output=True,
                text=True,
            ).stdout.strip()
            wt_head = run_git(
                self.path,
                ["rev-parse", "HEAD"],
                quiet=True,
                check=True,
                capture_output=True,
                text=True,
            ).stdout.strip()

            behind = int(
                run_git(
                    self.main_checkout_dir,
                    ["rev-list", "--count", f"{wt_head}..{main_head}"],
                    quiet=True,
                    check=True,
                    capture_output=True,
                    text=True,
                ).stdout.strip()
            )
            new = int(
                run_git(
                    self.main_checkout_dir,
                    ["rev-list", "--count", f"{main_head}..{wt_head}"],
                    quiet=True,
                    check=True,
                    capture_output=True,
                    text=True,
                ).stdout.strip()
            )

            if behind == 0 and new == 0:
                return SyncStatus.SYNCED, 0, 0
            if behind > 0 and new == 0:
                return SyncStatus.BEHIND, behind, 0
            if behind == 0 and new > 0:
                return SyncStatus.NEW, 0, new
            return SyncStatus.DIVERGED, behind, new
        except (subprocess.CalledProcessError, FileNotFoundError):
            return SyncStatus.UNKNOWN, 0, 0

    def acquire_lease(self, task_id: str | None = None) -> None:
        state = self.get_state()
        if state != WorktreeState.FREE:
            raise RuntimeError(
                f"Worktree '{self.name}' is not free (state: {state.value})"
            )

        try:
            self.meta_dir.mkdir(parents=True, exist_ok=True)
            fd = os.open(self.lease_file, os.O_WRONLY | os.O_CREAT | os.O_EXCL)
            lease_data = {
                "worktree_id": self.name,
                "pid": os.getpid(),
                "timestamp_sec": int(time.time()),
                "path": str(self.path),
            }
            if task_id:
                lease_data["task_id"] = task_id
            with os.fdopen(fd, "w") as f:
                json.dump(lease_data, f, separators=(",", ":"))
        except FileExistsError:
            raise RuntimeError(f"Worktree '{self.name}' is already leased")

        for bd in self.build_dirs():
            bd.backup_args()

    def release_lease(self) -> None:
        state = self.get_state()
        if state != WorktreeState.LEASED:
            raise RuntimeError(
                f"Cannot release '{self.name}': worktree is not leased (state: {state.value})"
            )

        for bd in self.build_dirs():
            bd.restore_args()

        # Rename the slot's jj workspaces from the task back to the slot's
        # name, so `jj log` shows which slots are free.
        self.rename_jj_workspaces(self.name)
        # jj keeps HEAD detached already.
        if not self.is_jj_workspace():
            try:
                run_git(
                    self.path, ["checkout", "--detach"], quiet=True, check=True
                )
            except Exception as e:
                print(
                    f"Warning: failed to detach branch in worktree '{self.name}': {e}",
                    file=sys.stderr,
                )

        try:
            if self.lease_file.exists():
                os.remove(self.lease_file)
        except OSError as e:
            raise RuntimeError(f"Failed to remove lease file: {e}")