from django.db import models


class GuidePage(models.Model):
    class Audience(models.TextChoices):
        SHARED = "shared", "Shared"
        BUYER = "buyer", "Buyer"
        OPS = "ops", "Operations"
        ADMIN = "admin", "Administrator"

    AUDIENCE_PREFIXES = (
        ("user-guides/index", Audience.SHARED),
        ("user-guides/buyer/", Audience.BUYER),
        ("user-guides/ops/", Audience.OPS),
        ("user-guides/admin/", Audience.ADMIN),
    )

    path = models.CharField(max_length=255, unique=True)
    title = models.CharField(max_length=255)
    audience = models.CharField(max_length=20, choices=Audience.choices)
    content = models.TextField(blank=True, default="")
    updated_at = models.DateTimeField()
    synced_at = models.DateTimeField(auto_now=True)

    class Meta:
        ordering = ["path"]

    def __str__(self):
        return self.title

    @property
    def page_slug(self):
        return self.path[len("user-guides/"):] if self.path.startswith("user-guides/") else self.path

    def preview(self, max_chars=180):
        for line in self.content.splitlines():
            line = line.strip()
            if not line or line.startswith(("#", "-", ">", "|", "*", "![", "```", "<")):
                continue
            text = line.replace("**", "").replace("`", "").replace("*", "").strip()
            if text:
                return text[:max_chars]
        return ""

    @classmethod
    def map_audience(cls, path):
        for prefix, audience in cls.AUDIENCE_PREFIXES:
            if path == prefix or path.startswith(prefix):
                return audience
        return None


# The help centre is scoped by PORTAL first, then by role. Which guides are
# listed depends on which portal you are standing in, not only on who you are:
# an admin browsing the buyer portal sees the buyer guides, because it is the
# buyer portal. The admin-only guides never surface there.
AUDIENCES_BY_PORTAL = {
    "portal": frozenset({GuidePage.Audience.SHARED, GuidePage.Audience.BUYER}),
    "ops": frozenset({GuidePage.Audience.SHARED, GuidePage.Audience.OPS}),
}

# Extra audiences unlocked by ROLE, per portal. Admin guides are ops-side
# material, so they are only ever added inside the ops portal.
ADMIN_EXTRA_AUDIENCES = {
    "ops": frozenset({GuidePage.Audience.ADMIN}),
}


def allowed_audiences(portal, role=None, is_superuser=False):
    """Guide audiences visible in `portal` ("portal" or "ops") for this user."""
    allowed = set(AUDIENCES_BY_PORTAL.get(portal, frozenset()))
    if is_superuser or role == "admin":
        allowed |= ADMIN_EXTRA_AUDIENCES.get(portal, frozenset())
    return allowed