"""Locate `resource` blocks in .tf files and intersect with changed lines."""
from __future__ import annotations

import re
from dataclasses import dataclass
from pathlib import Path


_HEADER_RE = re.compile(
    r'^\s*resource\s+"(?P<type>[^"]+)"\s+"(?P<name>[^"]+)"\s*\{'
)


@dataclass(frozen=True)
class ResourceBlock:
    type: str
    name: str
    start: int
    end: int


def find_resource_blocks(path: Path) -> list[ResourceBlock]:
    """Locate top-level `resource` blocks by tracking brace depth."""
    text = path.read_text()
    lines = text.splitlines()
    blocks: list[ResourceBlock] = []
    i = 0
    while i < len(lines):
        line = lines[i]
        m = _HEADER_RE.match(line)
        if not m:
            i += 1
            continue
        start = i + 1
        depth = line.count("{") - line.count("}")
        j = i
        while depth > 0 and j + 1 < len(lines):
            j += 1
            depth += lines[j].count("{") - lines[j].count("}")
        blocks.append(ResourceBlock(
            type=m.group("type"),
            name=m.group("name"),
            start=start,
            end=j + 1,
        ))
        i = j + 1
    return blocks


def _intersects(a: tuple[int, int], b: tuple[int, int]) -> bool:
    return not (a[1] < b[0] or b[1] < a[0])


def touched_resources(
    path: Path, added_ranges: list[tuple[int, int]],
) -> list[ResourceBlock]:
    if not added_ranges:
        return []
    blocks = find_resource_blocks(path)
    out: list[ResourceBlock] = []
    for blk in blocks:
        if any(_intersects((blk.start, blk.end), r) for r in added_ranges):
            out.append(blk)
    return out