"""Praxis path schema — YAML DSL -> Pydantic (SLICE-05, D-037, REQ-PATH-02).

Defines the typed model for a 6-week competency path. Each week lists the
scenarios it exercises and a mastery gate (>= required_scenarios distinct
scenarios passed, >= required_score mean score per D-032). Loaded from
`paths/<slug>.yaml` by server/paths/engine.py.

Per PRD section 6.4 (D-037): exactly 6 weeks, numbered 1..6 sequentially.
"""

from __future__ import annotations

from pydantic import BaseModel, Field, ValidationError, field_validator, model_validator

_REQUIRED_WEEKS = 6
_MIN_WEEK = 1
_MAX_WEEK = 6
_DEFAULT_REQUIRED_SCENARIOS = 3
_DEFAULT_REQUIRED_SCORE = 3.5


class WeekGate(BaseModel):
    """Mastery gate config for one week (D-032).

    A week's gate opens when the learner has passed >= required_scenarios
    distinct scenarios with a mean score >= required_score across those
    passing scenarios.
    """

    required_scenarios: int = Field(
        _DEFAULT_REQUIRED_SCENARIOS,
        ge=1,
        description="Min distinct passed scenarios to open the gate (D-032 default 3)",
    )
    required_score: float = Field(
        _DEFAULT_REQUIRED_SCORE,
        ge=0.0,
        description="Min mean score across passing scenarios to open the gate (D-032 default 3.5)",
    )


class PathWeek(BaseModel):
    """One week in a 6-week competency path."""

    week: int = Field(..., ge=_MIN_WEEK, le=_MAX_WEEK, description="Week number 1..6")
    title: str = Field(..., min_length=1, description="Human-readable week title")
    scenario_ids: list[str] = Field(
        ..., min_length=1, description="Scenario ids exercised this week (authored in SLICE-06)"
    )
    gate: WeekGate = Field(default_factory=WeekGate, description="Mastery gate for this week")

    @field_validator("scenario_ids")
    @classmethod
    def _scenario_ids_unique(cls, v: list[str]) -> list[str]:
        if len(v) != len(set(v)):
            dupes = sorted({s for s in v if v.count(s) > 1})
            raise ValueError(f"duplicate scenario_ids in week: {dupes}")
        return v


class Path(BaseModel):
    """A 6-week competency path (D-037, PRD section 6.4)."""

    slug: str = Field(..., min_length=1, description="Path slug, e.g. 'customer_service'")
    name: str = Field(..., min_length=1, description="Human-readable path name")
    skill: str = Field(..., min_length=1, description="Skill this path develops (matches a rubric id)")
    weeks: list[PathWeek] = Field(..., description="Exactly 6 weeks, numbered 1..6 sequentially")

    @model_validator(mode="after")
    def _validate_weeks(self) -> Path:
        if len(self.weeks) != _REQUIRED_WEEKS:
            raise ValueError(
                f"path must have exactly {_REQUIRED_WEEKS} weeks (D-037 / PRD section 6.4), "
                f"got {len(self.weeks)}"
            )
        seen = sorted(w.week for w in self.weeks)
        expected = list(range(_MIN_WEEK, _MAX_WEEK + 1))
        if seen != expected:
            raise ValueError(
                f"week numbers must be exactly 1..{_REQUIRED_WEEKS} sequential, got {seen}"
            )
        dupes = [w.week for w in self.weeks if [x.week for x in self.weeks].count(w.week) > 1]
        if dupes:
            raise ValueError(f"duplicate week numbers: {sorted(set(dupes))}")
        return self

    def week_by_number(self, week: int) -> PathWeek | None:
        for w in self.weeks:
            if w.week == week:
                return w
        return None

    def all_scenario_ids(self) -> list[str]:
        ids: list[str] = []
        for w in self.weeks:
            ids.extend(w.scenario_ids)
        return ids


__all__ = [
    "Path",
    "PathWeek",
    "WeekGate",
    "ValidationError",
]