# GPLv3 license
# Copyright Lutra Consulting Limited

import os
import json
import base64
import sqlite3
import tempfile
import glob

from qgis.PyQt.QtCore import QVariant

from qgis.PyQt.QtGui import QColor

from qgis.core import (
    QgsApplication,
    QgsVectorLayer,
    QgsFeature,
    QgsGeometry,
    QgsFields,
    QgsField,
    QgsProject,
    QgsLayerTreeLayer,
    QgsConditionalStyle,
    QgsSymbolLayerUtils,
    QgsMarkerSymbol,
    QgsLineSymbol,
    QgsFillSymbol,
    QgsRuleBasedRenderer,
    QgsWkbTypes,
)

from .utils import pygeodiff, get_schema

diff_layers_list = []


class ColumnSchema:
    """Describes GPKG table column"""

    def __init__(self, name, datatype, pkey):
        self.name = name
        self.datatype = datatype
        self.pkey = pkey

    def __repr__(self):
        return f"<ColumnSchema {self.name} ({self.datatype})>"


class TableSchema:
    """Describes GPKG table"""

    def __init__(self, name, columns):
        self.name = name
        self.columns = columns

    def geometry_column_index(self):
        """Returns index of the geometry column or -1 if it does not exist"""
        for i, col in enumerate(self.columns):
            if col.datatype == "geometry":
                return i
        return -1

    def __repr__(self):
        return f"<TableSchema {self.name}>"


def old_value_for_column_by_index(entry_changes, i):
    """Retrieve previous (old) column value for given column index"""
    for ch in entry_changes:
        if ch["column"] == i:
            return ch["old"]
    raise ValueError("Expected value for column, but missing")


def get_row_from_db(db_conn, schema_table, entry_changes):
    """
    Fetches a single row from DB's table based on the values of pkeys
    in changeset entry
    """
    c = db_conn.cursor()
    where_bits = []
    for i, col in enumerate(schema_table.columns):
        if col.pkey:
            where_bits.append('"{}" = {}'.format(col.name, old_value_for_column_by_index(entry_changes, i)))

    c.execute('SELECT * FROM "{}" WHERE {}'.format(schema_table.name, " AND ".join(where_bits)))
    return c.fetchone()


def parse_gpkg_geom_encoding(wkb_with_gpkg_hdr):
    """Parse header of GPKG WKB and return WKB geometry"""
    flag_byte = wkb_with_gpkg_hdr[3]
    envelope_byte = (flag_byte & 14) >> 1
    envelope_size = {0: 0, 1: 32, 2: 48, 3: 48, 4: 64}[envelope_byte]
    hdr_size = 8 + envelope_size
    wkb = wkb_with_gpkg_hdr[hdr_size:]
    return wkb


def parse_db_schema(db_file):
    """Parse GPKG file schema and return map of tables"""
    schema_json = get_schema(db_file)

    tables = {}  # key: name, value: TableSchema
    for tbl in schema_json:
        columns = []
        for col in tbl["columns"]:
            columns.append(ColumnSchema(col["name"], col["type"], "primary_key" in col and col["primary_key"]))

        tables[tbl["table"]] = TableSchema(tbl["table"], columns)
    return tables


def db_schema_from_json(schema_json):
    """Create map of tables from the schema JSON file"""
    tables = {}  # key: name, value: TableSchema
    for tbl in schema_json:
        columns = []
        for col in tbl["columns"]:
            columns.append(ColumnSchema(col["name"], col["type"], "primary_key" in col and col["primary_key"]))

        tables[tbl["table"]] = TableSchema(tbl["table"], columns)
    return tables


def parse_diff(geodiff, diff_file):
    """
    Parse binary GeoDiff changeset and return map of changes per table
    as follows

    key: table name, value: list of tuples (type, changes)
    """
    tmp_file = tempfile.NamedTemporaryFile(delete=False)
    tmp_file.close()

    geodiff.list_changes(diff_file, tmp_file.name)
    with open(tmp_file.name, encoding="utf-8") as f:
        diff_json = json.load(f)
    os.unlink(tmp_file.name)

    diff_entries = diff_json["geodiff"]

    # group diff entries by tables
    diff_tables = {}  # key: table name, value: list of tuples (type, changes)
    for diff_entry in diff_entries:
        entry_table = diff_entry["table"]
        entry_type = diff_entry["type"]
        entry_changes = diff_entry["changes"]

        if entry_table not in diff_tables:
            diff_tables[entry_table] = []
        diff_tables[entry_table].append((entry_type, entry_changes))

    return diff_tables


def create_field_list(schema_table):
    """
    Creates QgsFields object from table schema as well as a mapping
    between table columns and fields indices
    """
    columns_to_fields = {}  # some columns (e.g. geometry) may be skipped

    fields = QgsFields()
    for i, column in enumerate(schema_table.columns):
        if column.datatype == "integer":
            t = QVariant.Int
        elif column.datatype == "text":
            t = QVariant.String
        elif column.datatype == "double":
            t = QVariant.Double
        elif column.datatype == "date":
            t = QVariant.Date
        elif column.datatype == "datetime":
            t = QVariant.DateTime
        elif column.datatype == "boolean":
            t = QVariant.Bool
        elif column.datatype == "blob":
            t = QVariant.QByteArray
        elif column.datatype == "geometry":
            continue
        else:
            raise ValueError(f"Unknow column type '{column.datatype}' for column '{column.name}'")
        columns_to_fields[i] = fields.count()
        f = QgsField(column.name, t)
        fields.append(f)

    fields.append(QgsField("geometry", QVariant.String))
    old_fields = QgsFields()
    for f in fields:
        old_fields.append(QgsField("_old_" + f.name(), f.type()))
    fields.extend(old_fields)
    fields.append(QgsField("_op", QVariant.String))

    return fields, columns_to_fields


def diff_table_to_features(diff_table, schema_table, fields, cols_to_flds, db_conn=None):
    """
    Converts a diff into list of QgsFeatures.

    Input is list of tuples (type, changes) where type is 'insert'/'update'/'delete'
    and changes is a list of dicts. Each dict with 'column', 'old', 'new' (old/new optional)
    """
    column_names = [column.name for column in schema_table.columns]
    features = []

    fld_geometry_idx = fields.indexOf("geometry")
    fld_old_offset = fld_geometry_idx + 1

    geom_col_index = schema_table.geometry_column_index()

    for entry_type, entry_changes in diff_table:
        f = QgsFeature(fields)
        row = [None for i in range(len(column_names))]

        f["_op"] = entry_type

        if entry_type == "update" and db_conn is not None:
            # try to fill in unchanged columns from the database
            db_row = get_row_from_db(db_conn, schema_table, entry_changes)

            for i in range(len(db_row)):
                if i == geom_col_index:
                    if db_row[i] == None:
                        continue
                    wkb = parse_gpkg_geom_encoding(db_row[i])
                    g = QgsGeometry()
                    g.fromWkb(wkb)
                    f.setGeometry(g)

                    f[fld_geometry_idx] = g.asWkt()
                    f[fld_geometry_idx + fld_old_offset] = g.asWkt()
                    continue
                else:
                    f[cols_to_flds[i]] = db_row[i]
                    f[cols_to_flds[i] + fld_old_offset] = db_row[i]

            # try to fill in the old columns from the diff
            for entry_change in entry_changes:
                i = entry_change["column"]
                if "old" in entry_change:
                    if i == geom_col_index:
                        if entry_change["old"] == None:
                            # Empty geometry
                            continue
                        wkb_with_gpkg_hdr = base64.decodebytes(entry_change["old"].encode("ascii"))
                        wkb = parse_gpkg_geom_encoding(wkb_with_gpkg_hdr)
                        g = QgsGeometry()
                        g.fromWkb(wkb)
                        f.setGeometry(g)

                        f[fld_geometry_idx] = g.asWkt()
                        f[fld_geometry_idx + fld_old_offset] = g.asWkt()
                    else:
                        f[cols_to_flds[i] + fld_old_offset] = entry_change["old"]

        for entry_change in entry_changes:
            i = entry_change["column"]
            if "new" in entry_change:
                value = entry_change["new"]
            elif "old" in entry_change:
                value = entry_change["old"]
            else:
                value = "?"

            if i == geom_col_index:
                if value == None:
                    # Empty geometry
                    continue
                wkb_with_gpkg_hdr = base64.decodebytes(value.encode("ascii"))
                wkb = parse_gpkg_geom_encoding(wkb_with_gpkg_hdr)
                g = QgsGeometry()
                g.fromWkb(wkb)
                f.setGeometry(g)

                f[fld_geometry_idx] = g.asWkt()
            else:
                f[cols_to_flds[i]] = value

        features.append(f)

    return features


def get_table_name(layer):
    """ "Returns name of the GPKG table name for the given vector layer"""
    table_name = ""
    if "layername" not in layer.source():
        sublayers = layer.dataProvider().subLayers()
        table_name = sublayers[0].split("!!::!!")[1]
    else:
        table_name = layer.source().partition("|layername=")[2]

    return table_name


def get_local_changes(geodiff, db_file, mp):
    """Creates changeset containing local changes in the given GPKG file."""
    f_name = os.path.split(db_file)[1]
    base_path = mp.fpath_meta(f_name)

    if not os.path.exists(base_path):
        return None

    diff_file = tempfile.NamedTemporaryFile(delete=False)
    diff_file.close()

    geodiff.create_changeset(base_path, db_file, diff_file.name)
    return diff_file.name


def make_local_changes_layer(mp, layer):
    geodiff = pygeodiff.GeoDiff()

    layer_path = layer.source().split("|")[0]
    base_file = mp.fpath_meta(os.path.split(layer_path)[1])
    diff_path = get_local_changes(geodiff, layer_path, mp)

    if diff_path is None:
        return None, f"Failed to retrieve changes, as there is no base file for layer '{layer.name()}'"

    db_schema = parse_db_schema(layer_path)
    diff = parse_diff(geodiff, diff_path)
    table_name = get_table_name(layer)

    if not diff or table_name not in diff.keys():
        return None, f"No local changes found in layer '{layer.name()}'"

    fields, cols_to_fields = create_field_list(db_schema[table_name])

    db_conn = None  # no ref. db
    db_conn = sqlite3.connect(base_file)

    features = diff_table_to_features(diff[table_name], db_schema[table_name], fields, cols_to_fields, db_conn)

    # create diff layer
    vl = QgsVectorLayer(
        f"{QgsWkbTypes.displayString(layer.wkbType())}?crs={layer.sourceCrs().authid()}",
        f"[Local changes] {layer.name()}",
        "memory",
    )
    if not vl.isValid():
        return None, f"Failed to create memory layer for local changes"

    vl.dataProvider().addAttributes(fields)
    vl.updateFields()
    vl.dataProvider().addFeatures(features)

    style_diff_layer(vl, db_schema[table_name])
    return vl, ""


def make_version_changes_layers(project_path, version):
    geodiff = pygeodiff.GeoDiff()

    layers = []
    version_dir = os.path.join(project_path, ".mergin", ".cache", f"v{version}")
    for f in glob.iglob(f"{version_dir}/*.gpkg"):
        gpkg_file = os.path.join(version_dir, f)
        schema_file = gpkg_file + "-schema.json"
        if not os.path.exists(schema_file):
            geodiff.schema("sqlite", "", gpkg_file, schema_file)

        changeset_file = find_changeset_file(f, version_dir)
        if changeset_file is None:
            continue

        with open(schema_file, encoding="utf-8") as fl:
            data = fl.read()
            schema_json = json.loads(data.replace("\n", "")).get("geodiff_schema")

        db_schema = db_schema_from_json(schema_json)
        diff = parse_diff(geodiff, changeset_file)

        for table_name in diff.keys():
            if table_name.startswith("gpkg_"):
                # db schema reported by geodiff exclude layer named "gpkg_*"
                # We skip it in the layer displayed to the user
                continue
            fields, cols_to_fields = create_field_list(db_schema[table_name])
            geom_type, geom_crs = get_layer_geometry_info(schema_json, table_name)

            db_conn = None  # no ref. db
            db_conn = sqlite3.connect(gpkg_file)

            features = diff_table_to_features(diff[table_name], db_schema[table_name], fields, cols_to_fields, db_conn)

            # create diff layer
            if geom_type is None:
                continue

            uri = f"{geom_type}?crs=epsg:{geom_crs}" if geom_crs else geom_type
            vl = QgsVectorLayer(uri, table_name, "memory")
            if not vl.isValid():
                continue

            vl.dataProvider().addAttributes(fields)
            vl.updateFields()
            vl.dataProvider().addFeatures(features)

            style_diff_layer(vl, db_schema[table_name])
            layers.append(vl)

    return layers


def find_changeset_file(file_name, version_dir):
    """Returns path to the diff file for the given version file"""
    for f in glob.iglob(f"{version_dir}/*.gpkg-diff*"):
        if f.startswith(file_name):
            return os.path.join(version_dir, f)
    return None


def get_layer_geometry_info(schema_json, table_name):
    """Returns geometry type and CRS for a given table"""
    for tbl in schema_json:
        if tbl["table"] == table_name:
            for col in tbl["columns"]:
                if col["type"] == "geometry":
                    return col["geometry"]["type"], col["geometry"]["srs_id"]
            return "NoGeometry", ""

    return None, None


def style_diff_layer(layer, schema_table):
    """Apply conditional styling and symbology to diff layer"""
    ### setup conditional styles!
    st = layer.conditionalStyles()
    color_red = QColor("#ffdce0")
    color_green = QColor("#dcffe4")
    color_yellow = QColor("#fff5b1")

    # full row for insert / delete
    cs_insert = QgsConditionalStyle()
    cs_insert.setName("insert")
    cs_insert.setRule("_op = 'insert'")
    cs_insert.setBackgroundColor(color_green)
    cs_delete = QgsConditionalStyle()
    cs_delete.setName("delete")
    cs_delete.setRule("_op = 'delete'")
    cs_delete.setBackgroundColor(color_red)
    st.setRowStyles([cs_insert, cs_delete])

    # field style for each updated field
    for column in schema_table.columns:
        if column.datatype == "geometry":
            col_name = "geometry"
        else:
            col_name = column.name
        cs = QgsConditionalStyle()
        cs.setName("update")
        cs.setRule(f'"_op" = \'update\' AND "{col_name}" IS NOT "_old_{col_name}"')
        cs.setBackgroundColor(color_yellow)
        st.setFieldStyles(col_name, [cs])

    # set up which fields are shown in the attribute table
    cfg = layer.attributeTableConfig()
    flds = layer.fields()
    for i, fld in enumerate(flds):
        if fld.name().startswith("_old_") or fld.name() == "_op":
            cfg.setColumnHidden(i, True)
    layer.setAttributeTableConfig(cfg)

    # set up styling of the layer
    darker_factor = 150
    if layer.geometryType() == QgsWkbTypes.PointGeometry:
        point_symbol_base = {
            "name": "circle",
            "outline_style": "solid",
            "outline_width": "0.4",
            "outline_width_unit": "MM",
            "size": "5",
            "size_unit": "MM",
        }
        point_symbol_insert = dict(point_symbol_base)
        point_symbol_insert["color"] = QgsSymbolLayerUtils.encodeColor(color_green)
        point_symbol_insert["outline_color"] = QgsSymbolLayerUtils.encodeColor(color_green.darker(darker_factor))
        point_symbol_update = dict(point_symbol_base)
        point_symbol_update["color"] = QgsSymbolLayerUtils.encodeColor(color_yellow)
        point_symbol_update["outline_color"] = QgsSymbolLayerUtils.encodeColor(color_yellow.darker(darker_factor))
        point_symbol_delete = dict(point_symbol_base)
        point_symbol_delete["color"] = QgsSymbolLayerUtils.encodeColor(color_red)
        point_symbol_delete["outline_color"] = QgsSymbolLayerUtils.encodeColor(color_red.darker(darker_factor))

        root_rule = QgsRuleBasedRenderer.Rule(None)
        root_rule.appendChild(
            QgsRuleBasedRenderer.Rule(
                QgsMarkerSymbol.createSimple(point_symbol_insert), 0, 0, "_op = 'insert'", "Insert"
            )
        )
        root_rule.appendChild(
            QgsRuleBasedRenderer.Rule(
                QgsMarkerSymbol.createSimple(point_symbol_update), 0, 0, "_op = 'update'", "Update"
            )
        )
        root_rule.appendChild(
            QgsRuleBasedRenderer.Rule(
                QgsMarkerSymbol.createSimple(point_symbol_delete), 0, 0, "_op = 'delete'", "Delete"
            )
        )
        r = QgsRuleBasedRenderer(root_rule)
        layer.setRenderer(r)
    elif layer.geometryType() == QgsWkbTypes.LineGeometry:
        line_symbol_base = {
            "capstyle": "square",
            "joinstyle": "bevel",
            "line_style": "solid",
            "line_width": "0.86",
            "line_width_unit": "MM",
        }
        line_symbol_insert = dict(line_symbol_base)
        line_symbol_insert["line_color"] = QgsSymbolLayerUtils.encodeColor(color_green)
        line_symbol_update = dict(line_symbol_base)
        line_symbol_update["line_color"] = QgsSymbolLayerUtils.encodeColor(color_yellow)
        line_symbol_delete = dict(line_symbol_base)
        line_symbol_delete["line_color"] = QgsSymbolLayerUtils.encodeColor(color_red)

        root_rule = QgsRuleBasedRenderer.Rule(None)
        root_rule.appendChild(
            QgsRuleBasedRenderer.Rule(QgsLineSymbol.createSimple(line_symbol_insert), 0, 0, "_op = 'insert'", "Insert")
        )
        root_rule.appendChild(
            QgsRuleBasedRenderer.Rule(QgsLineSymbol.createSimple(line_symbol_update), 0, 0, "_op = 'update'", "Update")
        )
        root_rule.appendChild(
            QgsRuleBasedRenderer.Rule(QgsLineSymbol.createSimple(line_symbol_delete), 0, 0, "_op = 'delete'", "Delete")
        )
        r = QgsRuleBasedRenderer(root_rule)
        layer.setRenderer(r)
    elif layer.geometryType() == QgsWkbTypes.PolygonGeometry:
        fill_symbol_base = {
            "joinstyle": "bevel",
            "style": "solid",
            "outline_style": "solid",
            "outline_width": "0.26",
            "outline_width_unit": "MM",
        }
        fill_symbol_insert = dict(fill_symbol_base)
        fill_symbol_insert["color"] = QgsSymbolLayerUtils.encodeColor(color_green)
        fill_symbol_insert["outline_color"] = QgsSymbolLayerUtils.encodeColor(color_green.darker(darker_factor))
        fill_symbol_update = dict(fill_symbol_base)
        fill_symbol_update["color"] = QgsSymbolLayerUtils.encodeColor(color_yellow)
        fill_symbol_update["outline_color"] = QgsSymbolLayerUtils.encodeColor(color_yellow.darker(darker_factor))
        fill_symbol_delete = dict(fill_symbol_base)
        fill_symbol_delete["color"] = QgsSymbolLayerUtils.encodeColor(color_red)
        fill_symbol_delete["outline_color"] = QgsSymbolLayerUtils.encodeColor(color_red.darker(darker_factor))

        root_rule = QgsRuleBasedRenderer.Rule(None)
        root_rule.appendChild(
            QgsRuleBasedRenderer.Rule(QgsFillSymbol.createSimple(fill_symbol_insert), 0, 0, "_op = 'insert'", "Insert")
        )
        root_rule.appendChild(
            QgsRuleBasedRenderer.Rule(QgsFillSymbol.createSimple(fill_symbol_update), 0, 0, "_op = 'update'", "Update")
        )
        root_rule.appendChild(
            QgsRuleBasedRenderer.Rule(QgsFillSymbol.createSimple(fill_symbol_delete), 0, 0, "_op = 'delete'", "Delete")
        )
        r = QgsRuleBasedRenderer(root_rule)
        layer.setRenderer(r)
