import sip
from qgis.core import (
    QgsVectorLayer,
    QgsFeature,
    QgsGeometry,
    QgsPointXY,
    QgsField,
    QgsProject,
    QgsMessageLog,
    QgsPalLayerSettings,
    QgsVectorLayerSimpleLabeling,
    QgsTextFormat,
    QgsTextBufferSettings,
    QgsMarkerSymbol,
    QgsSingleSymbolRenderer,
    Qgis,
)
from PyQt5.QtCore import QVariant
from PyQt5.QtGui import QColor

from .api_client import ApiClient


class LocationLayerManager:
    """Creates and manages the 'BAPE Bridge' memory vector layer."""

    _NAME_OK  = "BAPE Bridge"
    _NAME_ERR = "🔴 BAPE Bridge"

    def __init__(self, api_client: ApiClient):
        self._api_client = api_client
        self.layer: QgsVectorLayer | None = None

    # ------------------------------------------------------------------
    # Public API
    # ------------------------------------------------------------------

    def create_layer(self) -> None:
        """Create the memory layer, add it to the project and load initial features.

        Raises:
            Exception: if the initial API fetch fails (layer is still added to the
                       project but will be empty until reload_layer() succeeds).
        """
        self.layer = QgsVectorLayer("Point?crs=EPSG:4326", self._NAME_OK, "memory")
        if not self.layer.isValid():
            raise RuntimeError("Failed to create memory layer.")

        provider = self.layer.dataProvider()
        provider.addAttributes([
            QgsField("id", QVariant.String),
            QgsField("name", QVariant.String),
        ])
        self.layer.updateFields()

        QgsProject.instance().addMapLayer(self.layer)
        self._configure_marker()
        self._configure_labels()

        # Initial load — set error name on failure so the layer is visible
        # in the panel but clearly marked as not yet connected.
        try:
            self._do_reload()
        except Exception:
            self.layer.setName(self._NAME_ERR)
            raise

    def reload_layer(self) -> bool:
        """Fetch fresh data and replace all features in the layer.

        Returns:
            True on success, False on failure (existing features are kept).
        """
        if self.layer is None or not self.layer.isValid():
            return False

        try:
            self._do_reload()
            return True
        except Exception as exc:
            QgsMessageLog.logMessage(
                f"Layer reload failed, keeping existing features: {exc}",
                "BAPEBridge",
                Qgis.Warning,
            )
            self.layer.setName(self._NAME_ERR)
            self.layer.emitStyleChanged()
            return False

    def clear_layer(self) -> None:
        """Remove all features from the layer without fetching new data."""
        if self.layer is None or not self.layer.isValid():
            return
        self.layer.dataProvider().truncate()
        self.layer.updateExtents()
        self.layer.triggerRepaint()

    def remove_layer(self) -> None:
        """Remove the layer from the project and release the reference."""
        if self.layer is not None:
            if not sip.isdeleted(self.layer):
                layer_id = self.layer.id()
                if QgsProject.instance().mapLayer(layer_id) is not None:
                    QgsProject.instance().removeMapLayer(layer_id)
            self.layer = None

    # ------------------------------------------------------------------
    # Private helpers
    # ------------------------------------------------------------------

    def _configure_marker(self) -> None:
        """Set a green filled triangle marker at size 3."""
        symbol = QgsMarkerSymbol.createSimple({
            "name": "triangle",
            "color": "72,123,182,255",
            "size": "3",
        })
        self.layer.setRenderer(QgsSingleSymbolRenderer(symbol))

    def _configure_labels(self) -> None:
        """Enable simple labels showing the 'name' field next to each point."""
        buffer = QgsTextBufferSettings()
        buffer.setEnabled(True)
        buffer.setColor(QColor("black"))
        buffer.setSize(0.4)

        text_format = QgsTextFormat()
        text_format.setColor(QColor("white"))
        text_format.setBuffer(buffer)

        pal = QgsPalLayerSettings()
        pal.fieldName = "name"
        pal.enabled = True
        pal.setFormat(text_format)
        self.layer.setLabeling(QgsVectorLayerSimpleLabeling(pal))
        self.layer.setLabelsEnabled(True)

    def _do_reload(self) -> None:
        """Core fetch-and-replace logic. Raises on any failure."""
        locations = self._api_client.fetch_locations()

        provider = self.layer.dataProvider()
        provider.truncate()

        features = [self._build_feature(loc) for loc in locations]
        provider.addFeatures(features)

        self.layer.updateExtents()
        self.layer.triggerRepaint()
        self.layer.setName(self._NAME_OK)
        self.layer.emitStyleChanged()

        QgsMessageLog.logMessage(
            f"Loaded {len(features)} location(s).",
            "BAPEBridge",
            Qgis.Info,
        )

    def _build_feature(self, loc: dict) -> QgsFeature:
        feature = QgsFeature(self.layer.fields())
        feature.setGeometry(
            QgsGeometry.fromPointXY(QgsPointXY(loc["longitude"], loc["latitude"]))
        )
        feature["id"] = loc["id"]
        feature["name"] = loc["name"]
        return feature