import uuid

from django.conf import settings
from django.core.files.storage import default_storage
from django.db import models
from django.utils.translation import gettext_lazy as _

from .validators import validate_receipt_file


class Project(models.Model):
    name = models.CharField(max_length=255)
    code = models.CharField(max_length=50, blank=True)
    is_active = models.BooleanField(default=True)
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)

    class Meta:
        ordering = ["name"]

    def __str__(self):
        if self.code:
            return f"{self.code} – {self.name}"
        return self.name


class Claim(models.Model):
    class Status(models.TextChoices):
        PENDING = "pending", _("Pending")
        APPROVED = "approved", _("Approved")
        REJECTED = "rejected", _("Rejected")

    class Currency(models.TextChoices):
        SEK = "SEK", _("Swedish krona (SEK)")
        EUR = "EUR", _("Euro (EUR)")
        USD = "USD", _("US dollar (USD)")
        GBP = "GBP", _("British pound (GBP)")

    submitted_by = models.ForeignKey(
        settings.AUTH_USER_MODEL,
        null=True,
        blank=True,
        on_delete=models.SET_NULL,
        related_name="claims_submitted",
    )
    full_name = models.CharField(max_length=255)
    email = models.EmailField()
    amount = models.DecimalField(max_digits=10, decimal_places=2)
    currency = models.CharField(
        max_length=3,
        choices=Currency.choices,
        default=Currency.SEK,
    )
    description = models.TextField(help_text=_("Describe what the reimbursement is for"))
    account_number = models.CharField(max_length=50)
    receipt = models.FileField(
        upload_to="receipts/",
        blank=True,
        null=True,
        validators=[validate_receipt_file],
    )
    project = models.ForeignKey(
        Project,
        null=True,
        blank=True,
        on_delete=models.SET_NULL,
        related_name="claims",
    )
    status = models.CharField(max_length=20, choices=Status.choices, default=Status.PENDING)
    decision_note = models.TextField(blank=True)
    paid_at = models.DateTimeField(null=True, blank=True)
    paid_by = models.ForeignKey(
        settings.AUTH_USER_MODEL,
        null=True,
        blank=True,
        on_delete=models.SET_NULL,
        related_name="claims_marked_paid",
    )
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)

    class Meta:
        ordering = ["-created_at"]

    def __str__(self):
        project = f" [{self.project}]" if self.project else ""
        return f"{self.full_name} – {self.amount} {self.currency}{project} ({self.get_status_display()})"

    @property
    def is_paid(self):
        return self.paid_at is not None

    def add_log(self, *, action, performed_by=None, from_status=None, to_status=None, note=""):
        return ClaimLog.objects.create(
            claim=self,
            action=action,
            from_status=from_status,
            to_status=to_status or self.status,
            note=note or "",
            performed_by=performed_by,
        )

    def save(self, *args, **kwargs):
        if self.receipt and not kwargs.pop("skip_receipt_rename", False):
            original_name = self.receipt.name or ""
            ext = original_name.rsplit(".", 1)[-1] if "." in original_name else "dat"
            new_name = self._generate_unique_receipt_name(ext)
            self.receipt.name = new_name
        super().save(*args, **kwargs)

    def _generate_unique_receipt_name(self, ext):
        ext = ext.lower()
        for _ in range(10):
            candidate = f"receipts/{uuid.uuid4().hex}.{ext}"
            if not default_storage.exists(candidate):
                return candidate
        return f"receipts/{uuid.uuid4().hex}.{ext}"


class ClaimLog(models.Model):
    class Action(models.TextChoices):
        CREATED = "created", _("Submitted")
        STATUS_CHANGED = "status_changed", _("Status changed")
        MARKED_PAID = "marked_paid", _("Marked as paid")
        PROJECT_CHANGED = "project_changed", _("Project changed")
        DETAILS_EDITED = "details_edited", _("Details edited")

    claim = models.ForeignKey(Claim, related_name="logs", on_delete=models.CASCADE)
    action = models.CharField(max_length=32, choices=Action.choices)
    from_status = models.CharField(
        max_length=20,
        choices=Claim.Status.choices,
        null=True,
        blank=True,
    )
    to_status = models.CharField(max_length=20, choices=Claim.Status.choices)
    note = models.TextField(blank=True)
    performed_by = models.ForeignKey(
        settings.AUTH_USER_MODEL,
        null=True,
        blank=True,
        on_delete=models.SET_NULL,
        related_name="claim_logs",
    )
    created_at = models.DateTimeField(auto_now_add=True)

    class Meta:
        ordering = ["-created_at"]

    def __str__(self):
        return f"{self.get_action_display()} ({self.created_at:%Y-%m-%d %H:%M})"