"""Data-quality chapter (CALIDAD) for AutomaticEDA.

Builds the quality chapter from a ``TableProfile`` of the ``eda`` group. The
chapter answers, in Spanish and as tables, the three things the user asked for:

1. **En qué se basa la calidad** — an intro paragraph explaining the criteria and
   their weights (completeness, validity, consistency) before any number, plus a
   table-level summary (global score and aggregates).
2. **Scores por columna** — a table with, per column, the total quality score and
   its breakdown into completeness / validity / consistency.
3. **Problemas en español** — a second table listing, per column, the readable
   issues in Spanish (kept separate from the type ``flags``).

The breakdown and the issues are NOT recomputed here: they come from the registry
function ``column_quality_score`` (group ``eda``), which already derives
``{score, completeness, validity, consistency, issues}`` from the ColumnProfile.
This chapter is render-only — it consumes that function and lays the result out
as model blocks; the renderers paginate tables (splitting by rows, repeating the
header) and wrap long cells so nothing is ever cut.

Contract: build_<id>(profile, ctx) -> Chapter | None ; CHAPTER_VERSION = "x.y.z".
"""

from __future__ import annotations

from .. import model

# Reuse the registry's pure quality function (group ``eda``). Import defensively:
# if the package cannot be imported for any reason the chapter degrades to the
# per-column ``quality_score`` already present in the profile instead of failing.
try:  # pragma: no cover - import wiring
    from ...column_quality_score import column_quality_score as _column_quality_score
except Exception:  # noqa: BLE001 - never let an import error abort the document.
    _column_quality_score = None

CHAPTER_VERSION = "1.0.0"
CHAPTER_ID = "calidad"
CHAPTER_TITLE = "Calidad"

# Weights mirror column_quality_score: completeness 0.5, validity 0.3,
# consistency 0.2. Kept here only to render the human explanation; the actual
# numbers always come from the function so the two never drift in computation.
_CRITERIA_INTRO = (
    "La calidad de cada columna es un score de 0 a 100 que combina tres "
    "criterios, cada uno con un peso:\n\n"
    "- **Completitud (peso 50%)**: proporción de valores presentes (sin nulos "
    "ni vacíos). Una columna con muchos nulos baja de score.\n"
    "- **Validez (peso 30%)**: los valores son coherentes con su tipo y rango "
    "esperado (penaliza outliers y semánticas declaradas que no coinciden).\n"
    "- **Consistencia (peso 20%)**: la columna aporta información útil (penaliza "
    "columnas constantes o identificadores de cardinalidad muy alta).\n\n"
    "Score = 100 × (0,5·completitud + 0,3·validez + 0,2·consistencia). "
    "Los problemas detectados por columna se listan en español más abajo."
)

# Cap for the joined issues cell so a single row never grows taller than a page;
# the remainder is summarized as "(+N más)" instead of being silently dropped.
_ISSUES_MAXLEN = 160


def _fmt_score(value) -> str:
    """Format a 0-100 score as ``NN / 100`` (or a placeholder)."""
    if value is None:
        return "—"
    try:
        num = float(value)
    except (TypeError, ValueError):
        return str(value)
    if num != num:  # NaN
        return "—"
    text = f"{num:.1f}".rstrip("0").rstrip(".")
    return f"{text} / 100"


def _fmt_unit_pct(value) -> str:
    """Format a 0-1 fraction as a percentage (``95%``)."""
    if value is None:
        return "—"
    try:
        return f"{float(value) * 100:.0f}%"
    except (TypeError, ValueError):
        return str(value)


def _quality_of(col: dict) -> dict:
    """Return ``{score, completeness, validity, consistency, issues}`` for a column.

    Uses the registry ``column_quality_score`` when available; otherwise falls
    back to the per-column ``quality_score`` already in the profile (number only,
    empty breakdown/issues). Never raises.
    """
    if not isinstance(col, dict):
        col = {}
    if _column_quality_score is not None:
        try:
            res = _column_quality_score(col)
            if isinstance(res, dict):
                return res
        except Exception:  # noqa: BLE001 - degrade instead of aborting.
            pass
    # Fallback: only the final score is available pre-computed in the profile.
    return {
        "score": col.get("quality_score"),
        "completeness": None,
        "validity": None,
        "consistency": None,
        "issues": [],
    }


def _join_issues(issues) -> str:
    """Join Spanish issue strings into one cell, truncating overly long lists.

    The renderer wraps cell text, but a column with many long issues could make a
    single row taller than a whole page; cap the length and append ``(+N más)``
    so the count of hidden issues is honest rather than silently lost.
    """
    if not isinstance(issues, (list, tuple)) or not issues:
        return ""
    parts = [model._safe_str(i).strip() for i in issues]
    parts = [p for p in parts if p]
    if not parts:
        return ""
    out = []
    used = 0
    for idx, part in enumerate(parts):
        extra = len(part) + (2 if out else 0)
        if used + extra > _ISSUES_MAXLEN and out:
            remaining = len(parts) - idx
            out.append(f"(+{remaining} más)")
            return "; ".join(out)
        out.append(part)
        used += extra
    return "; ".join(out)


def _columns_with_quality(profile: dict):
    """Yield ``(col, quality_dict)`` for every column dict in the profile."""
    cols = profile.get("columns") or []
    for c in cols:
        if isinstance(c, dict):
            yield c, _quality_of(c)


def _summary_block(profile: dict, evaluated: list):
    """Table-level KVTable: global score and quality aggregates."""
    rows = []
    score = profile.get("quality_score")
    rows.append(("Calidad global", _fmt_score(score)))
    rows.append(("Columnas evaluadas", str(len(evaluated))))

    comps = [q.get("completeness") for _, q in evaluated
             if isinstance(q.get("completeness"), (int, float))]
    vals = [q.get("validity") for _, q in evaluated
            if isinstance(q.get("validity"), (int, float))]
    cons = [q.get("consistency") for _, q in evaluated
            if isinstance(q.get("consistency"), (int, float))]
    if comps:
        rows.append(("Completitud media", _fmt_unit_pct(sum(comps) / len(comps))))
    if vals:
        rows.append(("Validez media", _fmt_unit_pct(sum(vals) / len(vals))))
    if cons:
        rows.append(("Consistencia media", _fmt_unit_pct(sum(cons) / len(cons))))

    n_problem = sum(1 for _, q in evaluated if q.get("issues"))
    rows.append(("Columnas con problemas", str(n_problem)))

    # Extra table-wide quality signals already in the profile, when present.
    dup_pct = profile.get("duplicate_pct")
    if dup_pct is not None:
        rows.append(("Filas duplicadas", _fmt_unit_pct_or_pct(dup_pct)))
    null_cell_pct = profile.get("null_cell_pct")
    if null_cell_pct is not None:
        rows.append(("Celdas nulas (global)", _fmt_unit_pct_or_pct(null_cell_pct)))
    constant_cols = profile.get("constant_cols")
    if isinstance(constant_cols, (list, tuple)) and constant_cols:
        rows.append(("Columnas constantes", str(len(constant_cols))))
    all_null_cols = profile.get("all_null_cols")
    if isinstance(all_null_cols, (list, tuple)) and all_null_cols:
        rows.append(("Columnas 100% nulas", str(len(all_null_cols))))

    return model.KVTable(rows=rows, title="Resumen de calidad")


def _fmt_unit_pct_or_pct(value) -> str:
    """Format a value that may be a 0-1 fraction or an already-0-100 percentage."""
    try:
        num = float(value)
    except (TypeError, ValueError):
        return model._safe_str(value)
    if num != num:  # NaN
        return "—"
    pct = num * 100 if num <= 1.0 else num
    text = f"{pct:.1f}".rstrip("0").rstrip(".")
    return f"{text}%"


def _scores_block(evaluated: list):
    """DataTable with per-column score and its three-criteria breakdown."""
    header = ["Columna", "Calidad", "Completitud", "Validez", "Consistencia"]
    rows = []
    # Worst columns first so the reader sees the problems at the top.
    ordered = sorted(
        evaluated,
        key=lambda cq: (cq[1].get("score")
                        if isinstance(cq[1].get("score"), (int, float)) else 101.0),
    )
    for col, q in ordered:
        rows.append([
            col.get("name") or "(col)",
            _fmt_score(q.get("score")),
            _fmt_unit_pct(q.get("completeness")),
            _fmt_unit_pct(q.get("validity")),
            _fmt_unit_pct(q.get("consistency")),
        ])
    if not rows:
        return None
    return model.DataTable(header=header, rows=rows,
                           title="Scores de calidad por columna",
                           note="0 = peor, 100 = mejor; ordenado de peor a mejor")


def _issues_block(evaluated: list):
    """DataTable listing Spanish issues per column, or a Note when there are none."""
    header = ["Columna", "Problemas detectados (español)"]
    rows = []
    for col, q in evaluated:
        joined = _join_issues(q.get("issues"))
        if joined:
            rows.append([col.get("name") or "(col)", joined])
    if not rows:
        return model.Note(
            "No se detectaron problemas de calidad en las columnas evaluadas.")
    return model.DataTable(header=header, rows=rows,
                           title="Problemas de calidad por columna")


def build_calidad(profile: dict, ctx: dict):
    """Build the data-quality Chapter, or None if the profile has no columns.

    Reads everything defensively; returns ``None`` when there are no columns to
    score (the chapter does not apply), and never raises on a malformed profile.
    """
    profile = profile or {}
    if not isinstance(profile, dict):
        profile = {}
    ctx = ctx or {}

    evaluated = list(_columns_with_quality(profile))
    if not evaluated:
        return None  # no columns to score -> chapter does not apply.

    blocks = [
        model.Heading(text="Cómo se calcula la calidad", level=2),
        model.Markdown(text=_CRITERIA_INTRO),
        _summary_block(profile, evaluated),
        model.Heading(text="Scores por columna", level=2),
    ]
    scores = _scores_block(evaluated)
    if scores is not None:
        blocks.append(scores)
    blocks.append(model.Heading(text="Problemas detectados", level=2))
    blocks.append(_issues_block(evaluated))

    return model.Chapter(id=CHAPTER_ID, title=CHAPTER_TITLE,
                         version=CHAPTER_VERSION, blocks=blocks)