package mila

import (
	"errors"
	"fmt"
	"strings"
	"unicode/utf8"
)

type Config struct {
	MaxRouteLen    int
	MaxTextLen     int
	MaxTemplateLen int
}

func DefaultConfig() Config {
	return Config{
		MaxRouteLen:    3,
		MaxTextLen:     200,
		MaxTemplateLen: 200,
	}
}

type ValidationError struct {
	Field string `json:"field"`
	Msg   string `json:"message"`
}

func (e ValidationError) Error() string {
	return fmt.Sprintf("%s: %s", e.Field, e.Msg)
}

func Validate(cfg Config, state ContentState) error {
	cfg = normalizeConfig(cfg)

	state.Route = strings.TrimSpace(state.Route)
	state.Template = strings.TrimSpace(state.Template)

	if state.Route == "" {
		return ValidationError{Field: "route", Msg: "is required"}
	}
	if runeLen(state.Route) > cfg.MaxRouteLen {
		return ValidationError{Field: "route", Msg: fmt.Sprintf("must be at most %d characters", cfg.MaxRouteLen)}
	}
	if !utf8.ValidString(state.Route) {
		return ValidationError{Field: "route", Msg: "must be valid UTF-8"}
	}
	if !utf8.ValidString(state.Text) {
		return ValidationError{Field: "str", Msg: "must be valid UTF-8"}
	}
	if runeLen(state.Text) > cfg.MaxTextLen {
		return ValidationError{Field: "str", Msg: fmt.Sprintf("must be at most %d characters", cfg.MaxTextLen)}
	}
	if state.Template == "" {
		return ValidationError{Field: "tpl_name", Msg: "is required"}
	}
	if !utf8.ValidString(state.Template) {
		return ValidationError{Field: "tpl_name", Msg: "must be valid UTF-8"}
	}
	if runeLen(state.Template) > cfg.MaxTemplateLen {
		return ValidationError{Field: "tpl_name", Msg: fmt.Sprintf("must be at most %d characters", cfg.MaxTemplateLen)}
	}

	return nil
}

func IsValidationError(err error) bool {
	var target ValidationError
	return errors.As(err, &target)
}

func normalizeConfig(cfg Config) Config {
	def := DefaultConfig()
	if cfg.MaxRouteLen <= 0 {
		cfg.MaxRouteLen = def.MaxRouteLen
	}
	if cfg.MaxTextLen <= 0 {
		cfg.MaxTextLen = def.MaxTextLen
	}
	if cfg.MaxTemplateLen <= 0 {
		cfg.MaxTemplateLen = def.MaxTemplateLen
	}
	return cfg
}

func runeLen(s string) int {
	return utf8.RuneCountInString(s)
}