package table

import (
	"fmt"
	"io"
	"reflect"
)

type JSONPrinter struct {
	headers   []string
	writer    io.Writer
	continued bool
}

// Headers specify the table headers
func (p *JSONPrinter) Headers(headers ...string) error {
	p.headers = make([]string, len(headers), len(headers))
	for idx := range headers {
		p.headers[idx] = headers[idx]
	}
	_, err := fmt.Fprintf(p.writer, "[\n")
	return err
}

func (p *JSONPrinter) preamble() error {
	if p.continued {
		if _, err := fmt.Fprintf(p.writer, ",\n"); err != nil {
			return err
		}
	}
	if _, err := fmt.Fprintf(p.writer, "{\n"); err != nil {
		return err
	}
	return nil
}

// Fields add another row
func (p *JSONPrinter) Fields(fields ...interface{}) error {
	if err := p.preamble(); err != nil {
		return err
	}

	eol := ",\n"
	for idx := range fields {
		var err error

		if idx == len(fields)-1 {
			eol = "\n"
		}

		field := fields[idx]
		switch field.(type) {
		case string:
			_, err = fmt.Fprintf(p.writer, "\"%s\":\"%v\"%s", p.headers[idx], field, eol)
		case int, uint, int8, uint8, int32, uint32, int64, uint64, float32, float64:
			_, err = fmt.Fprintf(p.writer, "\"%s\": %v%s", p.headers[idx], field, eol)
		default:
			err = fmt.Errorf("unsupported field type : %s", reflect.TypeOf(field).Name())
		}
		if err != nil {
			return err
		}
	}
	p.continued = true
	_, err := fmt.Fprintf(p.writer, "}\n")
	return err
}

func (p *JSONPrinter) StringFields(fields ...string) error {
	if err := p.preamble(); err != nil {
		return err
	}

	eol := ",\n"
	for idx, field := range fields {
		if idx == len(fields)-1 {
			eol = "\n"
		}
		_, err := fmt.Fprintf(p.writer, "\"%s\":\"%v\"%s", p.headers[idx], field, eol)
		if err != nil {
			return err
		}
	}
	p.continued = true
	_, err := fmt.Fprintf(p.writer, "}\n")
	return err
}

// Flush implements the flush interface but for CVS printer is a noop
func (p *JSONPrinter) Flush() error {
	_, err := fmt.Fprintf(p.writer, "]\n")
	return err
}