"""`file_splitting` task generator."""
import json
import random
import shutil
from collections import defaultdict
from pathlib import Path

from ..base import (
    Generator, _VERIFY_HEADER, _render_verify, pad_to, _write, _para,
    _AUTHORS, _SONG_TITLES, _STUDENTS, _WORDS,
)


class FileSplitting(Generator):
    KEY = "file_splitting"
    CATEGORY_NAME = "File Splitting"
    DIFFICULTY = "L2"
    TAGS = ["file content", "split"]

    SRC = "combined.txt"
    DELIM = "-----"
    OUT_DIR = "parts"

    def build(self, env_dir, llm, rng):
        k = rng.randint(3, 5)
        sections = []
        for _ in range(k):
            sections.append("\n".join(_para(rng, rng.randint(2, 4))))
        content = ("\n" + self.DELIM + "\n").join(sections)
        _write(env_dir / self.SRC, content + "\n")
        return {"src": self.SRC, "delim": self.DELIM, "out_dir": self.OUT_DIR, "k": k}

    def description(self, spec):
        return (
            "Please use FileSystem tools to finish the following task:\n\n"
            "### Task: Split a combined file into parts\n\n"
            f"The file `{self.SRC}` contains several sections separated by lines that "
            f"consist of exactly `{self.DELIM}`.\n\n"
            f"1. Create a folder named `{self.OUT_DIR}/` in the test directory root.\n"
            f"2. Write each section, in order, to `{self.OUT_DIR}/part_1.txt`, "
            f"`{self.OUT_DIR}/part_2.txt`, … (1-based).\n"
            "3. Each part file contains only that section's text (no delimiter "
            "lines). Do not modify the original file."
        )

    def verify_src(self, spec):
        body = '''
C = json.loads(__CONSTS__)


def main():
    t = get_test_dir()
    src = t / C["src"]
    if not src.is_file():
        fail(f"source file missing: {C['src']}")
    sections = src.read_text(encoding="utf-8").split("\\n" + C["delim"] + "\\n")
    pdir = t / C["out_dir"]
    if not pdir.is_dir():
        fail(f"missing directory: {C['out_dir']}")
    for i, sec in enumerate(sections, 1):
        pf = pdir / f"part_{i}.txt"
        if not pf.is_file():
            fail(f"missing part file: part_{i}.txt")
        if pf.read_text(encoding="utf-8").strip() != sec.strip():
            fail(f"part_{i}.txt content does not match section {i}")
    extra = [p.name for p in pdir.iterdir() if p.is_file() and p.name not in
             {f"part_{i}.txt" for i in range(1, len(sections) + 1)}]
    if extra:
        fail(f"unexpected files in {C['out_dir']}: {extra}")
    ok(f"file correctly split into {len(sections)} parts")
    print("\\U0001f389 All checks passed!")
    sys.exit(0)


if __name__ == "__main__":
    main()
'''
        return _render_verify(body, {"src": spec["src"], "delim": spec["delim"], "out_dir": spec["out_dir"]})

    def solve(self, work_dir, spec):
        src = work_dir / spec["src"]
        sections = src.read_text(encoding="utf-8").split("\n" + spec["delim"] + "\n")
        pdir = work_dir / spec["out_dir"]
        pdir.mkdir(exist_ok=True)
        for i, sec in enumerate(sections, 1):
            _write(pdir / f"part_{i}.txt", sec.strip() + "\n")