"""Build a concrete workflow graph from a template + request parameters."""
import copy
import secrets
from typing import Any

from .errors import InvalidRequest

SEED_MAX = 2**63 - 1


def parse_size(size: str) -> tuple[int, int]:
    """Parse OpenAI `WxH` size strings (e.g. '1024x1024')."""
    try:
        w_str, h_str = size.lower().split("x", 1)
        width, height = int(w_str), int(h_str)
    except ValueError as e:
        raise InvalidRequest(f"invalid size '{size}', expected format 'WIDTHxHEIGHT'") from e
    if width <= 0 or height <= 0:
        raise InvalidRequest(f"invalid size '{size}', dimensions must be positive")
    return width, height


def new_seed(seed: int | None) -> int:
    if seed is None:
        return secrets.randbelow(SEED_MAX) + 1
    if not 0 <= seed <= SEED_MAX:
        raise InvalidRequest(f"seed must be between 0 and {SEED_MAX}")
    return seed


def build_workflow(
    template: dict[str, Any],
    mapping: dict[str, dict[str, str]],
    *,
    prompt: str,
    seed: int,
    size: str | None = None,
    image_name: str | None = None,
    negative: str = "",
) -> dict[str, Any]:
    """Deep-copy the template and inject request values per the node mapping."""
    graph = copy.deepcopy(template)

    def put(key: str, value: Any) -> None:
        spec = mapping.get(key)
        if spec is None:
            return
        node = graph.get(spec["node"])
        if node is None:
            raise InvalidRequest(f"mapping key '{key}' points to missing node '{spec['node']}'")
        node["inputs"][spec["field"]] = value

    put("prompt", prompt)
    put("negative", negative)
    put("seed", seed)
    if image_name is not None:
        put("image", image_name)
    if size is not None:
        spec = mapping.get("size")
        if spec is not None:
            width, height = parse_size(size)
            node = graph.get(spec["node"])
            if node is None:
                raise InvalidRequest(f"mapping key 'size' points to missing node '{spec['node']}'")
            node["inputs"][spec["width_field"]] = width
            node["inputs"][spec["height_field"]] = height
    return graph