package errors

import (
	"errors"
	"fmt"
	"strings"

	"github.com/lib/pq"
)

// ErrorId is an id that is unique to the error (not the instance of the error).
// The id should be generated using `make rand`, and used as the `errorid` param when calling `errors.New`
type ErrorId string

// Err provides the ability to specify a Msg, ErrorId, Code and Wrapped error.
// Errs must have a Code and ErrorId all other fields are optional. We've chosen Err
// over Error for the identifier to support the easy embedding of Errs.  Errs
// can be embedded without a conflict between the embedded Err and Err.Error().
type Err struct {
	// Code is the error's code, which can be used to get the error's
	// errorCodeInfo, which contains the error's Kind and Message
	Code Code

	// Unique ID used to identify the error being returned
	ErrorId ErrorId

	// Msg for the error
	Msg string

	// Wrapped is the error which this Err wraps and will be nil if there's no
	// error to wrap.
	Wrapped error
}

// New creates a new Err and supports the options of:
// WithMsg() - allows you to specify an optional error msg, if the default
// msg for the error Code is not sufficient.
// WithWrap() - allows you to specify
// an error to wrap
func New(c Code, errorid ErrorId, opt ...Option) error {
	opts := GetOpts(opt...)

	return &Err{
		Code:    c,
		ErrorId: errorid,
		Wrapped: opts.withErrWrapped,
		Msg:     opts.withErrMsg,
	}
}

// Wrap creates a new Err, but preserves the Code of the original error being wrapped
func Wrap(e error, errorid ErrorId, opt ...Option) error {
	var code Code
	if err, ok := e.(*Err); ok {
		// get code from wrapped error
		code = err.Code
	}
	opt = append(opt, WithWrap(e))
	return New(code, errorid, opt...)
}

// Convert will convert the error to a Boundary *Err (returning it as an error)
// and attempt to add a helpful error msg as well. If that's not possible, it
// will return nil
func Convert(e error, errorid ErrorId) *Err {
	if e == nil {
		return nil
	}
	if err, ok := e.(*Err); ok {
		return err
	}

	var pqError *pq.Error
	if As(e, &pqError) {
		if pqError.Code.Class() == "23" { // class of integrity constraint violations
			switch pqError.Code {
			case "23505": // unique_violation
				return New(NotUnique, errorid, WithMsg(pqError.Detail), WithWrap(ErrNotUnique)).(*Err)
			case "23502": // not_null_violation
				msg := fmt.Sprintf("%s must not be empty", pqError.Column)
				return New(NotNull, errorid, WithMsg(msg), WithWrap(ErrNotNull)).(*Err)
			case "23514": // check_violation
				msg := fmt.Sprintf("%s constraint failed", pqError.Constraint)
				return New(CheckConstraint, errorid, WithMsg(msg), WithWrap(ErrCheckConstraint)).(*Err)
			default:
				return New(NotSpecificIntegrity, errorid, WithMsg(pqError.Message)).(*Err)
			}
		}
		if pqError.Code == "42P01" {
			return New(MissingTable, errorid, WithMsg(pqError.Message)).(*Err)
		}
	}
	if errors.Is(e, ErrRecordNotFound) {
		return New(RecordNotFound, errorid, WithMsg(e.Error())).(*Err)
	}
	// unfortunately, we can't help.
	return nil
}

// Info about the Err
func (e *Err) Info() Info {
	if e == nil {
		return errorCodeInfo[Unknown]
	}
	return e.Code.Info()
}

// Error satisfies the error interface and returns a string representation of
// the Err
func (e *Err) Error() string {
	if e == nil {
		return ""
	}
	var s strings.Builder
	if e.ErrorId != "" {
		join(&s, ": ", string(e.ErrorId))
	}
	if e.Msg != "" {
		join(&s, ": ", e.Msg)
	}

	if info, ok := errorCodeInfo[e.Code]; ok {
		if e.Msg == "" {
			join(&s, ": ", info.Message) // provide a default.
			join(&s, ", ", info.Kind.String())
		} else {
			join(&s, ": ", info.Kind.String())
		}
	}
	join(&s, ": ", fmt.Sprintf("error #%d", e.Code))

	if e.Wrapped != nil {
		join(&s, ": \n", e.Wrapped.Error())
	}
	return s.String()
}

func join(str *strings.Builder, delim string, s string) {
	if str.Len() == 0 {
		_, _ = str.WriteString(s)
		return
	}
	_, _ = str.WriteString(delim + s)
}

// Unwrap implements the errors.Unwrap interface and allows callers to use the
// errors.Is() and errors.As() functions effectively for any wrapped errors.
func (e *Err) Unwrap() error {
	if e == nil {
		return nil
	}
	return e.Wrapped
}

// Is the equivalent of the std errors.Is, but allows Devs to only import
// this package for the capability.
func Is(err, target error) bool {
	return errors.Is(err, target)
}

// As is the equivalent of the std errors.As, and allows devs to only import
// this package for the capability.
func As(err error, target interface{}) bool {
	return errors.As(err, target)
}