package influxql

import (
	"encoding/json"
	"errors"
)

// Result represents a resultset returned from a single statement.
type Result struct {
	// StatementID is just the statement's position in the query. It's used
	// to combine statement results if they're being buffered in memory.
	StatementID int `json:"-"`
	Series      Rows
	Err         error
}

// MarshalJSON encodes the result into JSON.
func (r *Result) MarshalJSON() ([]byte, error) {
	// Define a struct that outputs "error" as a string.
	var o struct {
		Series []*Row `json:"series,omitempty"`
		Err    string `json:"error,omitempty"`
	}

	// Copy fields to output struct.
	o.Series = r.Series
	if r.Err != nil {
		o.Err = r.Err.Error()
	}

	return json.Marshal(&o)
}

// UnmarshalJSON decodes the data into the Result struct
func (r *Result) UnmarshalJSON(b []byte) error {
	var o struct {
		Series []*Row `json:"series,omitempty"`
		Err    string `json:"error,omitempty"`
	}

	err := json.Unmarshal(b, &o)
	if err != nil {
		return err
	}
	r.Series = o.Series
	if o.Err != "" {
		r.Err = errors.New(o.Err)
	}
	return nil
}