"""Deterministic Git history builder for suite-authored scenarios (no working tree)."""

from __future__ import annotations

import os

from pathlib import Path

import tempfile

from typing import Dict, List, Optional, Union

from .gitops import Git

# File spec: bytes (regular), ("exec", bytes), ("link", "target").

FileSpec = Union[bytes, tuple]

Files = Dict[str, FileSpec]

EPOCH = 1_750_000_000  # fixed, so imported Oak commit hashes are reproducible

class RepoBuilder(Git):

    def __init__(self, repo: Path, git_bin: str, home: Path):

        repo.mkdir(parents=True, exist_ok=True)

        super().__init__(repo, git_bin, home)

        self.run("init", "-q", "--object-format=sha1")

        self._tick = 0

    def commit(self, files: Files, parents: Optional[List[str]] = None, message: str = "c",

               when: Optional[int] = None, branch: Optional[str] = None) -> str:

        """Create a commit whose tree is exactly `files`. `when` is seconds since EPOCH

        (defaults to a monotone tick; may be negative to model clock skew)."""

        if when is None:

            self._tick += 60

            when = self._tick

        lines = []

        for path in sorted(files):

            spec = files[path]

            if isinstance(spec, bytes):

                mode, data = "100644", spec

            elif spec[0] == "exec":

                mode, data = "100755", spec[1]

            elif spec[0] == "link":

                mode, data = "120000", os.fsencode(spec[1])

            else:

                raise ValueError(f"bad file spec for {path}")

            oid = self.out("hash-object", "-w", "--stdin", input=data)

            lines.append(f"{mode} {oid}\t{path}")

        with tempfile.TemporaryDirectory(prefix="mergesuite-index-") as tmp:

            env = {"GIT_INDEX_FILE": str(Path(tmp) / "index")}

            self.run("update-index", "--add", "--index-info",

                     input=("\n".join(lines) + "\n").encode() if lines else b"", env_extra=env)

            tree = self.out("write-tree", env_extra=env)

        stamp = f"{EPOCH + when} +0000"

        args = ["commit-tree", tree]

        for p in parents or []:

            args += ["-p", p]  # order preserved: first parent first

        args += ["-m", message]

        commit = self.out(*args, env_extra={"GIT_AUTHOR_DATE": stamp, "GIT_COMMITTER_DATE": stamp})

        if branch:

            self.run("update-ref", f"refs/heads/{branch}", commit)

        return commit

def lines(*items: str) -> bytes:

    return "".join(f"{x}\n" for x in items).encode()