// normalizeStatement adds a default database and policy to the measurements in statement.
func (q *QueryExecutor) normalizeStatement(stmt influxql.Statement, defaultDatabase string) (err error) {
	// Track prefixes for replacing field names.
	prefixes := make(map[string]string)

	// Qualify all measurements.
	influxql.WalkFunc(stmt, func(n influxql.Node) {
		if err != nil {
			return
		}
		switch n := n.(type) {
		case *influxql.Measurement:
			e := q.normalizeMeasurement(n, defaultDatabase)
			if e != nil {
				err = e
				return
			}
			prefixes[n.Name] = n.Name
		}
	})
	if err != nil {
		return err
	}

	// Replace all variable references that used measurement prefixes.
	influxql.WalkFunc(stmt, func(n influxql.Node) {
		switch n := n.(type) {
		case *influxql.VarRef:
			for k, v := range prefixes {
				if strings.HasPrefix(n.Val, k+".") {
					n.Val = v + "." + influxql.QuoteIdent(n.Val[len(k)+1:])
				}
			}
		}
	})

	return
}

// uniqueTagValues returns a list of unique tag values used in an expression.
func (m *Measurement) uniqueTagValues(expr influxql.Expr) map[string][]string {
	// Track unique value per tag.
	tags := make(map[string]map[string]struct{})

	// Find all tag values referenced in the expression.
	influxql.WalkFunc(expr, func(n influxql.Node) {
		switch n := n.(type) {
		case *influxql.BinaryExpr:
			// Ignore operators that are not equality.
			if n.Op != influxql.EQ {
				return
			}

			// Extract ref and string literal.
			var key, value string
			switch lhs := n.LHS.(type) {
			case *influxql.VarRef:
				if rhs, ok := n.RHS.(*influxql.StringLiteral); ok {
					key, value = lhs.Val, rhs.Val
				}
			case *influxql.StringLiteral:
				if rhs, ok := n.RHS.(*influxql.VarRef); ok {
					key, value = rhs.Val, lhs.Val
				}
			}
			if key == "" {
				return
			}

			// Add value to set.
			if tags[key] == nil {
				tags[key] = make(map[string]struct{})
			}
			tags[key][value] = struct{}{}
		}
	})

	// Convert to map of slices.
	out := make(map[string][]string)
	for k, values := range tags {
		out[k] = make([]string, 0, len(values))
		for v := range values {
			out[k] = append(out[k], v)
		}
		sort.Strings(out[k])
	}
	return out
}

// normalizeStatement adds a default database and policy to the measurements in statement.
func (q *QueryExecutor) normalizeStatement(stmt influxql.Statement, defaultDatabase string) (err error) {
	// Track prefixes for replacing field names.
	prefixes := make(map[string]string)

	// Qualify all measurements.
	influxql.WalkFunc(stmt, func(n influxql.Node) {
		if err != nil {
			return
		}
		switch n := n.(type) {
		case *influxql.Measurement:
			e := q.normalizeMeasurement(n, defaultDatabase)
			if e != nil {
				err = e
				return
			}
			prefixes[n.Name] = n.Name
		}
	})
	return
}

// Ensure the SELECT statement can have its start and end time set
func TestSelectStatement_SetTimeRange(t *testing.T) {
	q := "SELECT sum(value) from foo where time < now() GROUP BY time(10m)"
	stmt, err := influxql.NewParser(strings.NewReader(q)).ParseStatement()
	if err != nil {
		t.Fatalf("invalid statement: %q: %s", stmt, err)
	}

	s := stmt.(*influxql.SelectStatement)
	min, max := influxql.TimeRange(s.Condition)
	start := time.Now().Add(-20 * time.Hour).Round(time.Second).UTC()
	end := time.Now().Add(10 * time.Hour).Round(time.Second).UTC()
	s.SetTimeRange(start, end)
	min, max = influxql.TimeRange(s.Condition)

	if min != start {
		t.Fatalf("start time wasn't set properly.\n  exp: %s\n  got: %s", start, min)
	}
	// the end range is actually one nanosecond before the given one since end is exclusive
	end = end.Add(-time.Nanosecond)
	if max != end {
		t.Fatalf("end time wasn't set properly.\n  exp: %s\n  got: %s", end, max)
	}

	// ensure we can set a time on a select that already has one set
	start = time.Now().Add(-20 * time.Hour).Round(time.Second).UTC()
	end = time.Now().Add(10 * time.Hour).Round(time.Second).UTC()
	q = fmt.Sprintf("SELECT sum(value) from foo WHERE time >= %ds and time <= %ds GROUP BY time(10m)", start.Unix(), end.Unix())
	stmt, err = influxql.NewParser(strings.NewReader(q)).ParseStatement()
	if err != nil {
		t.Fatalf("invalid statement: %q: %s", stmt, err)
	}

	s = stmt.(*influxql.SelectStatement)
	min, max = influxql.TimeRange(s.Condition)
	if start != min || end != max {
		t.Fatalf("start and end times weren't equal:\n  exp: %s\n  got: %s\n  exp: %s\n  got:%s\n", start, min, end, max)
	}

	// update and ensure it saves it
	start = time.Now().Add(-40 * time.Hour).Round(time.Second).UTC()
	end = time.Now().Add(20 * time.Hour).Round(time.Second).UTC()
	s.SetTimeRange(start, end)
	min, max = influxql.TimeRange(s.Condition)

	// TODO: right now the SetTimeRange can't override the start time if it's more recent than what they're trying to set it to.
	//       shouldn't matter for our purposes with continuous queries, but fix this later

	if min != start {
		t.Fatalf("start time wasn't set properly.\n  exp: %s\n  got: %s", start, min)
	}
	// the end range is actually one nanosecond before the given one since end is exclusive
	end = end.Add(-time.Nanosecond)
	if max != end {
		t.Fatalf("end time wasn't set properly.\n  exp: %s\n  got: %s", end, max)
	}

	// ensure that when we set a time range other where clause conditions are still there
	q = "SELECT sum(value) from foo WHERE foo = 'bar' and time < now() GROUP BY time(10m)"
	stmt, err = influxql.NewParser(strings.NewReader(q)).ParseStatement()
	if err != nil {
		t.Fatalf("invalid statement: %q: %s", stmt, err)
	}

	s = stmt.(*influxql.SelectStatement)

	// update and ensure it saves it
	start = time.Now().Add(-40 * time.Hour).Round(time.Second).UTC()
	end = time.Now().Add(20 * time.Hour).Round(time.Second).UTC()
	s.SetTimeRange(start, end)
	min, max = influxql.TimeRange(s.Condition)

	if min != start {
		t.Fatalf("start time wasn't set properly.\n  exp: %s\n  got: %s", start, min)
	}
	// the end range is actually one nanosecond before the given one since end is exclusive
	end = end.Add(-time.Nanosecond)
	if max != end {
		t.Fatalf("end time wasn't set properly.\n  exp: %s\n  got: %s", end, max)
	}

	// ensure the where clause is there
	hasWhere := false
	influxql.WalkFunc(s.Condition, func(n influxql.Node) {
		if ex, ok := n.(*influxql.BinaryExpr); ok {
			if lhs, ok := ex.LHS.(*influxql.VarRef); ok {
				if lhs.Val == "foo" {
					if rhs, ok := ex.RHS.(*influxql.StringLiteral); ok {
						if rhs.Val == "bar" {
							hasWhere = true
						}
					}
				}
			}
		}
	})
	if !hasWhere {
		t.Fatal("set time range cleared out the where clause")
	}
}