"""Explicit, administrator-controlled service grants for each effective level."""

import re

from django.core.exceptions import ImproperlyConfigured
from ldap3.core.exceptions import LDAPInvalidDnError
from ldap3.utils.dn import parse_dn


SERVICE_LINKS = {
    "Discourse · community forums": {
        "url": "https://discourse.eom.dev/",
        "favicon": "https://discourse.eom.dev/uploads/default/optimized/1X/_129430568242d1b7f853bb13ebea28b3f6af4e7_2_32x32.png",
    },
    "Gitea · Git hosting": {
        "url": "https://gitea.eom.dev/",
        "favicon": "https://gitea.eom.dev/assets/img/favicon.svg",
    },
    "Matrix · community chat": {
        "url": "https://element.eom.dev/",
        "favicon": "https://element.eom.dev/vector-icons/144.5a63bf2.png",
    },
    "Mastodon · social networking": {
        "url": "https://mastodon.eom.dev/",
        "favicon": "https://mastodon.eom.dev/packs/assets/favicon-48x48-DMnduFKh.png",
    },
    "PeerTube · video sharing": {
        "url": "https://peertube.eom.dev/",
        "favicon": "https://peertube.eom.dev/client/assets/images/favicon.png",
    },
}


def validate_service_groups(value, paid_levels):
    if not isinstance(value, dict):
        raise ImproperlyConfigured("Membership service groups must be an object mapping levels to lists of LDAP group DNs.")
    valid_levels = {0, *paid_levels}
    for level, groups in value.items():
        if not isinstance(level, str) or not re.fullmatch(r"0|[1-9][0-9]*", level) or int(level) not in valid_levels:
            raise ImproperlyConfigured("Service group levels must be 0 or a configured paid membership level.")
        if not isinstance(groups, list):
            raise ImproperlyConfigured("Each service group level must contain a list of LDAP group DNs.")
        seen = set()
        for dn in groups:
            if not isinstance(dn, str) or not dn or dn != dn.strip() or len(dn) > 1024 or any(ord(char) < 32 for char in dn):
                raise ImproperlyConfigured("Service group DNs must be nonempty valid LDAP DNs of at most 1024 characters.")
            try:
                parts = parse_dn(dn)
            except LDAPInvalidDnError:
                raise ImproperlyConfigured("Invalid LDAP service group DN.") from None
            if not parts or dn.casefold() in seen:
                raise ImproperlyConfigured("Service group DNs must be valid and unique within each level.")
            seen.add(dn.casefold())
    return value


def configured_groups(tiers, service_groups):
    """All managed targets, not only the groups this account currently earns."""
    return {tier["group_dn"] for tier in tiers.values()} | {
        dn for groups in service_groups.values() for dn in groups
    }


def service_names(level, service_groups):
    """Public labels from the same exact-level mapping used by reconciliation."""
    labels = {
        "dex users": "Dex · single sign-on",
        "discourse users": "Discourse · community forums",
        "gitea users": "Gitea · Git hosting",
        "matrix users": "Matrix · community chat",
        "mastodon users": "Mastodon · social networking",
        "peertube users": "PeerTube · video sharing",
    }
    names = []
    for dn in service_groups.get(str(level), []):
        # Show only a group's common name, never its directory hierarchy.
        common_name = next((value for attribute, value, _separator in parse_dn(dn) if attribute.casefold() == "cn"), "")
        if common_name.casefold() == "dex users":
            continue
        if not common_name:
            name = "Additional community service"
        else:
            # LDAP DN values escape reserved characters and UTF-8 bytes.
            raw = re.sub(r"\\([,=+<>#;\"\\ ])", r"\1", common_name)
            raw = re.sub(r"(?:\\[0-9a-fA-F]{2})+", lambda match: bytes.fromhex(match.group().replace("\\", "")).decode("utf-8", errors="replace"), raw)
            name = labels.get(raw.casefold(), re.sub(r"\s+users$", "", raw, flags=re.IGNORECASE))
        if name not in names:
            names.append(name)
    return names


def service_access_catalog(tiers, service_groups):
    """List each advertised service once, with the levels that include it."""
    level_labels = {0: "Open Lab"}
    level_labels.update({tier["level"]: tier["label"] for tier in tiers.values()})
    levels = sorted(level_labels)
    service_levels = {}
    for level in levels:
        for name in service_names(level, service_groups):
            service_levels.setdefault(name, []).append(level)

    catalog = []
    for name, included_levels in service_levels.items():
        if included_levels == levels:
            access = "Every membership level"
        else:
            ranges = []
            start = previous = included_levels[0]
            for level in included_levels[1:]:
                if level != previous + 1:
                    ranges.append((start, previous))
                    start = level
                previous = level
            ranges.append((start, previous))
            access = ", ".join(
                level_labels[first] if first == last else f"{level_labels[first]}–{level_labels[last]}"
                for first, last in ranges
            )
        catalog.append({"name": name, "access": access, **SERVICE_LINKS.get(name, {})})
    return catalog