package internal

import (
	"bytes"
	"fmt"
	"net/http"
	"reflect"
	"strconv"
	"time"

	"github.com/newrelic/go-agent/internal/jsonx"
)

const (
	// PanicErrorKlass is the error klass used for errors generated by
	// recovering panics in txn.End.
	PanicErrorKlass = "panic"
)

func panicValueMsg(v interface{}) string {
	switch val := v.(type) {
	case error:
		return val.Error()
	default:
		return fmt.Sprintf("%v", v)
	}
}

// TxnErrorFromPanic creates a new TxnError from a panic.
func TxnErrorFromPanic(now time.Time, v interface{}) TxnError {
	return TxnError{
		When:  now,
		Msg:   panicValueMsg(v),
		Klass: PanicErrorKlass,
	}
}

// TxnErrorFromError creates a new TxnError from an error.
func TxnErrorFromError(now time.Time, err error) TxnError {
	return TxnError{
		When:  now,
		Msg:   err.Error(),
		Klass: reflect.TypeOf(err).String(),
	}
}

// TxnErrorFromResponseCode creates a new TxnError from an http response code.
func TxnErrorFromResponseCode(now time.Time, code int) TxnError {
	return TxnError{
		When:  now,
		Msg:   http.StatusText(code),
		Klass: strconv.Itoa(code),
	}
}

// TxnError is an error captured in a Transaction.
type TxnError struct {
	When  time.Time
	Stack *StackTrace
	Msg   string
	Klass string
}

// TxnErrors is a set of errors captured in a Transaction.
type TxnErrors []*TxnError

// NewTxnErrors returns a new empty TxnErrors.
func NewTxnErrors(max int) TxnErrors {
	return make([]*TxnError, 0, max)
}

// Add adds a TxnError.
func (errors *TxnErrors) Add(e TxnError) {
	if len(*errors) < cap(*errors) {
		*errors = append(*errors, &e)
	}
}

func (h *harvestError) WriteJSON(buf *bytes.Buffer) {
	buf.WriteByte('[')
	jsonx.AppendFloat(buf, timeToFloatMilliseconds(h.When))
	buf.WriteByte(',')
	jsonx.AppendString(buf, h.txnName)
	buf.WriteByte(',')
	jsonx.AppendString(buf, h.Msg)
	buf.WriteByte(',')
	jsonx.AppendString(buf, h.Klass)
	buf.WriteByte(',')
	buf.WriteByte('{')
	w := jsonFieldsWriter{buf: buf}
	if nil != h.Stack {
		w.writerField("stack_trace", h.Stack)
	}
	w.writerField("agentAttributes", agentAttributesJSONWriter{
		attributes: h.attrs,
		dest:       destError,
	})
	w.writerField("userAttributes", userAttributesJSONWriter{
		attributes: h.attrs,
		dest:       destError,
	})
	w.rawField("intrinsics", JSONString("{}"))
	if h.requestURI != "" {
		w.stringField("request_uri", h.requestURI)
	}
	buf.WriteByte('}')
	buf.WriteByte(']')
}

// MarshalJSON is used for testing.
func (h *harvestError) MarshalJSON() ([]byte, error) {
	buf := &bytes.Buffer{}
	h.WriteJSON(buf)
	return buf.Bytes(), nil
}

type harvestError struct {
	TxnError
	txnName    string
	requestURI string
	attrs      *Attributes
}

type harvestErrors struct {
	errors []*harvestError
}

func newHarvestErrors(max int) *harvestErrors {
	return &harvestErrors{
		errors: make([]*harvestError, 0, max),
	}
}

func harvestErrorFromTxnError(e *TxnError, txnName string, requestURI string, attrs *Attributes) *harvestError {
	return &harvestError{
		TxnError:   *e,
		txnName:    txnName,
		requestURI: requestURI,
		attrs:      attrs,
	}
}

func addTxnError(errors *harvestErrors, e *TxnError, txnName string, requestURI string, attrs *Attributes) {
	he := harvestErrorFromTxnError(e, txnName, requestURI, attrs)
	errors.errors = append(errors.errors, he)
}

// MergeTxnErrors merges a transaction's errors into the harvest's errors.
func MergeTxnErrors(errors *harvestErrors, errs TxnErrors, txnName string, requestURI string, attrs *Attributes) {
	for _, e := range errs {
		if len(errors.errors) == cap(errors.errors) {
			return
		}
		addTxnError(errors, e, txnName, requestURI, attrs)
	}
}

func (errors *harvestErrors) Data(agentRunID string, harvestStart time.Time) ([]byte, error) {
	if 0 == len(errors.errors) {
		return nil, nil
	}
	estimate := 1024 * len(errors.errors)
	buf := bytes.NewBuffer(make([]byte, 0, estimate))
	buf.WriteByte('[')
	jsonx.AppendString(buf, agentRunID)
	buf.WriteByte(',')
	buf.WriteByte('[')
	for i, e := range errors.errors {
		if i > 0 {
			buf.WriteByte(',')
		}
		e.WriteJSON(buf)
	}
	buf.WriteByte(']')
	buf.WriteByte(']')
	return buf.Bytes(), nil
}

func (errors *harvestErrors) MergeIntoHarvest(h *Harvest) {}