"""
Suggests which serial-number fields are probably relevant for a ticket,
based on keywords in its line items (e.g. an item name containing
"Laptop" suggests Laptop Serial Number + Laptop Asset Tag). This is a
starting point staff can edit, not a hard schema - device types and
their field sets vary by company and grow over time, so the mapping
lives in a setting (DEVICE_FIELD_SUGGESTIONS), not code.

If a ticket has two line items that both match "phone" (e.g. a
termination processing two lines), the second gets numbered - "Phone
IMEI (2)" - rather than colliding with the first.
"""
from __future__ import annotations

from typing import List

from app import config


def parse_device_field_suggestions(raw: str) -> dict[str, list[str]]:
    """'keyword:Field One|Field Two,keyword2:Field Three' -> {keyword: [fields]}"""
    mapping: dict[str, list[str]] = {}
    for group in (raw or "").split(","):
        group = group.strip()
        if not group or ":" not in group:
            continue
        keyword, _, fields_str = group.partition(":")
        keyword = keyword.strip().lower()
        fields = [f.strip() for f in fields_str.split("|") if f.strip()]
        if keyword and fields:
            mapping[keyword] = fields
    return mapping


def get_device_field_suggestions() -> dict[str, list[str]]:
    return parse_device_field_suggestions(
        config.get("DEVICE_FIELD_SUGGESTIONS", config.DEFAULT_DEVICE_FIELD_SUGGESTIONS)
    )


def suggest_serial_fields(line_items: List[dict]) -> List[str]:
    """
    line_items: [{"sku": "OK401", "item_name": "Laptop - Dell Latitude..."}]
    Returns suggested field labels, in the order their matching keyword
    was found, numbered on repeat matches (e.g. two phone line items ->
    "Phone IMEI (1)", "Phone IMEI (2)", ...).

    Line items describing a shipping/return-label deliverable (e.g.
    "Shipping - Return Label Laptop") are skipped - they name a device
    type in passing but aren't an actual physical device to serialize,
    and would otherwise double-count against the real device line item.
    """
    keyword_map = get_device_field_suggestions()
    suggestions: List[str] = []
    match_counts: dict[str, int] = {}

    for item in line_items or []:
        item_name = item.get("item_name", "") or ""
        if item_name.strip().lower().startswith("shipping"):
            continue

        haystack = f"{item_name} {item.get('sku', '')}".lower()
        for keyword, fields in keyword_map.items():
            if keyword in haystack:
                match_counts[keyword] = match_counts.get(keyword, 0) + 1
                occurrence = match_counts[keyword]
                suffix = f" ({occurrence})" if occurrence > 1 else ""
                suggestions.extend(f"{field}{suffix}" for field in fields)

    return suggestions