"""
Domain model for the LinkedIn dataset.

The raw export is one very wide CSV row per person with several columns holding
serialised lists of dictionaries.  Storing that blob as-is would make filtering
and aggregation painful, so it is normalised into five tables:

    Company  <--- Experience ---> Profile <--- Education ---> School
                                     |
                                     +--- ProfileSkill ---> Skill

PostgreSQL is the source of truth.  Elasticsearch holds a denormalised
projection of the same data for search (see ``apps.search``); it can always be
rebuilt from these tables, which is why the index is disposable.
"""

from __future__ import annotations

from django.contrib.postgres.fields import ArrayField
from django.contrib.postgres.indexes import GinIndex
from django.contrib.postgres.search import SearchVectorField
from django.db import models
from django.utils.text import slugify


class TimeStampedModel(models.Model):
    created_at = models.DateTimeField(auto_now_add=True, db_index=True)
    updated_at = models.DateTimeField(auto_now=True)

    class Meta:
        abstract = True


class Company(TimeStampedModel):
    """An employer referenced by the current job or by a past experience."""

    external_id = models.CharField(max_length=128, blank=True, db_index=True)
    name = models.CharField(max_length=255, unique=True)
    industry = models.CharField(max_length=128, blank=True, db_index=True)
    size = models.CharField(max_length=32, blank=True, help_text="Head-count bucket, e.g. 51-200")
    founded = models.PositiveIntegerField(null=True, blank=True)
    website = models.CharField(max_length=255, blank=True)
    linkedin_url = models.CharField(max_length=255, blank=True)
    location_name = models.CharField(max_length=255, blank=True)
    country = models.CharField(max_length=128, blank=True, db_index=True)

    class Meta:
        ordering = ("name",)
        verbose_name_plural = "companies"

    def __str__(self) -> str:
        return self.name


class School(TimeStampedModel):
    name = models.CharField(max_length=255, unique=True)
    type = models.CharField(max_length=64, blank=True)
    website = models.CharField(max_length=255, blank=True)
    linkedin_url = models.CharField(max_length=255, blank=True)
    location_name = models.CharField(max_length=255, blank=True)
    country = models.CharField(max_length=128, blank=True)

    class Meta:
        ordering = ("name",)

    def __str__(self) -> str:
        return self.name


class Skill(TimeStampedModel):
    """
    A normalised skill.

    ``slug`` is the deduplication key: the raw data contains the same skill with
    different casing and spacing ("Team Building" / "team building").
    """

    name = models.CharField(max_length=128)
    slug = models.SlugField(max_length=140, unique=True)
    profile_count = models.PositiveIntegerField(
        default=0, db_index=True, help_text="Denormalised counter used to rank filter suggestions."
    )

    class Meta:
        ordering = ("-profile_count", "name")

    def __str__(self) -> str:
        return self.name

    @staticmethod
    def make_slug(name: str) -> str:
        return slugify(name)[:140] or name.strip().lower()[:140]


class Profile(TimeStampedModel):
    """A single person in the dataset."""

    class Gender(models.TextChoices):
        MALE = "male", "Male"
        FEMALE = "female", "Female"
        UNKNOWN = "", "Unknown"

    # -- Identity ----------------------------------------------------------
    external_id = models.CharField(
        max_length=64,
        blank=True,
        db_index=True,
        help_text="LinkedIn numeric id from the source export.",
    )
    full_name = models.CharField(max_length=255, db_index=True)
    first_name = models.CharField(max_length=128, blank=True)
    last_name = models.CharField(max_length=128, blank=True)
    gender = models.CharField(max_length=16, blank=True, choices=Gender.choices)
    linkedin_url = models.CharField(max_length=255, blank=True)
    linkedin_username = models.CharField(max_length=128, blank=True)
    github_url = models.CharField(max_length=255, blank=True)
    twitter_url = models.CharField(max_length=255, blank=True)

    # -- Current position --------------------------------------------------
    job_title = models.CharField(max_length=255, blank=True, db_index=True)
    job_title_role = models.CharField(
        max_length=64, blank=True, db_index=True, help_text="Coarse job family, e.g. engineering."
    )
    job_title_sub_role = models.CharField(max_length=64, blank=True)
    seniority_levels = ArrayField(
        models.CharField(max_length=32),
        default=list,
        blank=True,
        help_text="e.g. ['manager'], ['senior'], ['cxo'].",
    )
    current_company = models.ForeignKey(
        Company, null=True, blank=True, on_delete=models.SET_NULL, related_name="current_employees"
    )
    industry = models.CharField(max_length=128, blank=True, db_index=True)
    job_summary = models.TextField(blank=True)
    job_start_date = models.CharField(max_length=10, blank=True)

    # -- Location ----------------------------------------------------------
    location_name = models.CharField(max_length=255, blank=True)
    location_locality = models.CharField(max_length=128, blank=True)
    location_region = models.CharField(max_length=128, blank=True, db_index=True)
    location_country = models.CharField(max_length=128, blank=True, db_index=True)
    location_continent = models.CharField(max_length=64, blank=True)

    # -- Narrative & metrics ----------------------------------------------
    summary = models.TextField(blank=True)
    years_experience = models.PositiveSmallIntegerField(null=True, blank=True, db_index=True)
    inferred_salary = models.CharField(max_length=32, blank=True)
    connections = models.PositiveIntegerField(null=True, blank=True)
    interests = ArrayField(models.CharField(max_length=128), default=list, blank=True)
    languages = ArrayField(models.CharField(max_length=64), default=list, blank=True)

    # -- Contact details (PII: masked unless the caller is privileged) ------
    emails = models.JSONField(default=list, blank=True)
    phone_numbers = ArrayField(models.CharField(max_length=32), default=list, blank=True)

    skills = models.ManyToManyField(Skill, through="ProfileSkill", related_name="profiles")

    # -- Denormalised text, maintained by the importer ---------------------
    # PostgreSQL's ``SearchVector`` cannot traverse a many-to-many relation, so
    # the searchable text of the related rows is flattened here once at import
    # time.  This keeps the tsvector update to a single UPDATE statement and
    # keeps query time O(index lookup) instead of O(joins).
    skills_text = models.TextField(blank=True, editable=False)
    companies_text = models.TextField(blank=True, editable=False)
    education_text = models.TextField(blank=True, editable=False)

    # Materialised tsvector powering the PostgreSQL search backend.
    search_vector = SearchVectorField(null=True, editable=False)

    class Meta:
        ordering = ("full_name", "id")
        indexes = [
            GinIndex(fields=["search_vector"], name="profile_search_vector_gin"),
            GinIndex(fields=["seniority_levels"], name="profile_seniority_gin"),
            models.Index(
                fields=["location_country", "job_title_role"], name="profile_country_role"
            ),
        ]
        constraints = [
            models.UniqueConstraint(
                fields=["external_id"],
                condition=models.Q(external_id__gt=""),
                name="uniq_profile_external_id",
            )
        ]

    def __str__(self) -> str:
        return self.full_name

    @property
    def headline(self) -> str:
        """Short "Title at Company" line used in result cards."""
        company = self.current_company.name if self.current_company_id else ""
        if self.job_title and company:
            return f"{self.job_title} at {company}"
        return self.job_title or company


class ProfileSkill(models.Model):
    """Through table - keeps the original ordering of the skill list."""

    profile = models.ForeignKey(Profile, on_delete=models.CASCADE, related_name="profile_skills")
    skill = models.ForeignKey(Skill, on_delete=models.CASCADE, related_name="profile_skills")
    position = models.PositiveSmallIntegerField(default=0)

    class Meta:
        ordering = ("position",)
        constraints = [
            models.UniqueConstraint(fields=["profile", "skill"], name="uniq_profile_skill")
        ]

    def __str__(self) -> str:
        return f"{self.profile_id}:{self.skill_id}"


class Experience(TimeStampedModel):
    profile = models.ForeignKey(Profile, on_delete=models.CASCADE, related_name="experiences")
    company = models.ForeignKey(
        Company, null=True, blank=True, on_delete=models.SET_NULL, related_name="experiences"
    )
    company_name = models.CharField(max_length=255, blank=True)
    title = models.CharField(max_length=255, blank=True)
    title_role = models.CharField(max_length=64, blank=True)
    title_sub_role = models.CharField(max_length=64, blank=True)
    levels = ArrayField(models.CharField(max_length=32), default=list, blank=True)
    start_date = models.CharField(max_length=10, blank=True)
    end_date = models.CharField(max_length=10, blank=True)
    start_year = models.PositiveSmallIntegerField(null=True, blank=True, db_index=True)
    end_year = models.PositiveSmallIntegerField(null=True, blank=True)
    is_primary = models.BooleanField(default=False, db_index=True)
    location_name = models.CharField(max_length=255, blank=True)
    summary = models.TextField(blank=True)

    class Meta:
        ordering = ("-is_primary", "-start_year", "id")
        indexes = [models.Index(fields=["profile", "is_primary"], name="exp_profile_primary")]

    def __str__(self) -> str:
        return f"{self.title} @ {self.company_name}"


class Education(TimeStampedModel):
    profile = models.ForeignKey(Profile, on_delete=models.CASCADE, related_name="educations")
    school = models.ForeignKey(
        School, null=True, blank=True, on_delete=models.SET_NULL, related_name="educations"
    )
    school_name = models.CharField(max_length=255, blank=True)
    degrees = ArrayField(models.CharField(max_length=128), default=list, blank=True)
    majors = ArrayField(models.CharField(max_length=128), default=list, blank=True)
    minors = ArrayField(models.CharField(max_length=128), default=list, blank=True)
    gpa = models.DecimalField(max_digits=4, decimal_places=2, null=True, blank=True)
    start_date = models.CharField(max_length=10, blank=True)
    end_date = models.CharField(max_length=10, blank=True)
    end_year = models.PositiveSmallIntegerField(null=True, blank=True, db_index=True)

    class Meta:
        ordering = ("-end_year", "id")

    def __str__(self) -> str:
        return f"{self.school_name}"