from django.conf import settings
from django.db import models

from infrasynth.shared.enums import ApprovalStrategy
from infrasynth.tenancy.mixins import TenantOwnedModel


class Workflow(TenantOwnedModel):
    slug = models.SlugField(max_length=100)
    name = models.CharField(max_length=200)
    description = models.TextField(blank=True)
    is_active = models.BooleanField(default=True)
    created_by = models.ForeignKey(
        settings.AUTH_USER_MODEL,
        on_delete=models.SET_NULL,
        null=True,
        blank=True,
        related_name="+",
    )

    class Meta:
        db_table = "workflows_definition"
        constraints = [
            models.UniqueConstraint(fields=["tenant", "slug"], name="uniq_workflow_slug_per_tenant"),
        ]

    def __str__(self):
        return self.name


class WorkflowNode(TenantOwnedModel):
    class NodeType(models.TextChoices):
        START = "start", "Start"
        INTERMEDIATE = "intermediate", "Intermediate"
        END = "end", "End"

    workflow = models.ForeignKey(Workflow, on_delete=models.CASCADE, related_name="nodes")
    name = models.CharField(max_length=200)
    node_type = models.CharField(max_length=20, choices=NodeType.choices, default=NodeType.INTERMEDIATE)
    min_approvals = models.PositiveSmallIntegerField(default=1)
    approval_strategy = models.CharField(
        max_length=20,
        choices=ApprovalStrategy.choices,
        default=ApprovalStrategy.ALL,
    )
    position_x = models.IntegerField(default=0)
    position_y = models.IntegerField(default=0)

    class Meta:
        db_table = "workflows_node"
        constraints = [models.UniqueConstraint(fields=["workflow", "name"], name="uniq_node_name_per_workflow")]

    def __str__(self):
        return f"{self.workflow.slug}:{self.name}"


class Transition(TenantOwnedModel):
    from_node = models.ForeignKey(WorkflowNode, on_delete=models.CASCADE, related_name="outgoing_transitions")
    to_node = models.ForeignKey(WorkflowNode, on_delete=models.CASCADE, related_name="incoming_transitions")
    condition_slug = models.CharField(max_length=100, blank=True)
    is_default = models.BooleanField(default=False)

    class Meta:
        db_table = "workflows_transition"
        constraints = [
            models.UniqueConstraint(fields=["from_node", "condition_slug"], name="uniq_transition_condition"),
        ]

    def __str__(self):
        return f"{self.from_node} \u2192 {self.to_node}"


class WorkflowInstance(TenantOwnedModel):
    class Status(models.TextChoices):
        IN_PROGRESS = "in_progress", "In Progress"
        COMPLETED = "completed", "Completed"
        CANCELLED = "cancelled", "Cancelled"

    workflow = models.ForeignKey(Workflow, on_delete=models.CASCADE, related_name="instances")
    current_node = models.ForeignKey(
        WorkflowNode,
        on_delete=models.SET_NULL,
        null=True,
        blank=True,
        related_name="+",
    )
    owner = models.ForeignKey(
        settings.AUTH_USER_MODEL,
        on_delete=models.SET_NULL,
        null=True,
        blank=True,
        related_name="+",
    )
    status = models.CharField(max_length=20, choices=Status.choices, default=Status.IN_PROGRESS)
    started_at = models.DateTimeField(auto_now_add=True)
    completed_at = models.DateTimeField(null=True, blank=True)
    metadata = models.JSONField(default=dict)

    class Meta:
        db_table = "workflows_instance"
        indexes = [models.Index(fields=["tenant_id", "status"])]

    def __str__(self):
        return f"{self.workflow.slug}#{self.pk}"


class NodeAssignment(TenantOwnedModel):
    instance = models.ForeignKey(WorkflowInstance, on_delete=models.CASCADE, related_name="assignments")
    node = models.ForeignKey(WorkflowNode, on_delete=models.CASCADE, related_name="assignments")
    user = models.ForeignKey(settings.AUTH_USER_MODEL, on_delete=models.CASCADE, related_name="+")
    visit_number = models.IntegerField(default=1)
    is_required = models.BooleanField(default=True)
    has_processed = models.BooleanField(default=False)
    decision = models.CharField(max_length=50, null=True, blank=True)
    comments = models.TextField(blank=True)
    submitted_data = models.JSONField(default=dict, null=True, blank=True)
    processed_at = models.DateTimeField(null=True, blank=True)

    class Meta:
        db_table = "workflows_node_assignment"
        indexes = [models.Index(fields=["tenant_id", "has_processed"])]

    def __str__(self):
        return f"{self.instance}#{self.node.name}@{self.user}"


class WorkflowObserver(TenantOwnedModel):
    instance = models.ForeignKey(WorkflowInstance, on_delete=models.CASCADE, related_name="observers")
    user = models.ForeignKey(settings.AUTH_USER_MODEL, on_delete=models.CASCADE, related_name="+")

    class Meta:
        db_table = "workflows_observer"
        constraints = [models.UniqueConstraint(fields=["instance", "user"], name="uniq_observer_per_instance")]

    def __str__(self):
        return f"{self.instance}\u2192{self.user}"


class WorkflowAwareModel(TenantOwnedModel):
    """Abstract mixin for domain models that participate in a workflow."""

    workflow_instance = models.ForeignKey(
        WorkflowInstance,
        on_delete=models.SET_NULL,
        null=True,
        blank=True,
        related_name="+",
    )

    class Meta:
        abstract = True