package bot

import (
	"errors"
	"fmt"
	"html"
	"strconv"
	"strings"
	"time"

	cepis "cep.is/go"

	"cep.is/telegrambot/internal/lookup"
)

// ParseMode is the formatting Telegram applies to every message this bot sends.
// HTML is used rather than Markdown because address data is arbitrary text from
// the Correios database and escaping three characters is a complete defence,
// while Markdown has a dozen context-dependent ones.
const ParseMode = "HTML"

// FormatAddress renders an address as the HTML body of a Telegram message.
//
// The coordinate section is where this function earns its keep. A CEP whose
// precisao is "logradouro" gets a map link: the point is a stretch of street
// and following it lands where the user expects. A CEP whose precisao is
// "localidade" gets no link at all, because the CEP is the entire municipality
// and its point is the centroid — dropping a pin there looks exactly like an
// address and is wrong by kilometres. That case is labelled, given its radius
// in kilometres, and told plainly not to be used as a delivery point.
func FormatAddress(address *cepis.Address) string {
	var b strings.Builder

	b.WriteString("📮 <b>" + esc(address.FormattedCEP()) + "</b>\n")

	if line := streetLine(address); line != "" {
		b.WriteString(esc(line) + "\n")
	}
	if address.Unidade != "" {
		b.WriteString(esc(address.Unidade) + "\n")
	}
	b.WriteString(esc(placeLine(address)) + "\n")
	if line := metaLine(address); line != "" {
		b.WriteString("<i>" + esc(line) + "</i>\n")
	}

	b.WriteString(geoSection(address))
	return strings.TrimRight(b.String(), "\n")
}

// InlineTitle is the one-line label shown in the inline results list.
func InlineTitle(address *cepis.Address) string {
	if address.Logradouro != "" {
		return address.FormattedCEP() + " — " + address.Logradouro
	}
	return address.FormattedCEP() + " — " + address.Localidade
}

// InlineDescription is the second line of an inline result. It repeats the
// municipality warning, so someone picking a result from the list sees it
// before sending the message rather than after.
func InlineDescription(address *cepis.Address) string {
	parts := []string{placeLine(address)}
	if address.Geo != nil && !address.Geo.IsPrecise() {
		parts = append(parts, "CEP geral do município")
	}
	return strings.Join(parts, " · ")
}

func streetLine(address *cepis.Address) string {
	parts := []string{}
	if address.Logradouro != "" {
		parts = append(parts, address.Logradouro)
	}
	if address.Complemento != "" {
		parts = append(parts, address.Complemento)
	}
	return strings.Join(parts, ", ")
}

func placeLine(address *cepis.Address) string {
	place := address.Localidade
	if address.UF != "" {
		place += "/" + address.UF
	}
	if address.Bairro != "" {
		return address.Bairro + " — " + place
	}
	return place
}

func metaLine(address *cepis.Address) string {
	parts := []string{}
	if address.Regiao != "" {
		parts = append(parts, address.Regiao)
	}
	if address.DDD != "" {
		parts = append(parts, "DDD "+address.DDD)
	}
	if address.IBGE != "" {
		parts = append(parts, "IBGE "+address.IBGE)
	}
	return strings.Join(parts, " · ")
}

func geoSection(address *cepis.Address) string {
	geo := address.Geo
	if geo == nil {
		return "\n<i>Sem coordenada para este CEP na base do IBGE.</i>\n"
	}

	if geo.IsPrecise() {
		return "\n🗺 <a href=\"" + esc(mapURL(geo.Lat, geo.Lon)) + "\">Ver no mapa</a>\n" +
			"<i>Precisão de logradouro — o ponto é o trecho de rua (raio aprox. " +
			esc(formatRadius(geo.RaioM)) + ").</i>\n"
	}

	return "\n⚠️ <b>CEP geral de município</b> — não corresponde a um endereço.\n" +
		"A única coordenada disponível é o centroide de " + esc(address.Localidade) +
		", com raio aproximado de " + esc(formatRadius(geo.RaioM)) +
		". Não serve como ponto de entrega nem para calcular frete, " +
		"por isso não mando link de mapa.\n" +
		"<i>" + esc(coordText(geo.Lat, geo.Lon)) + "</i>\n"
}

func mapURL(lat, lon float64) string {
	latText := strconv.FormatFloat(lat, 'f', 6, 64)
	lonText := strconv.FormatFloat(lon, 'f', 6, 64)
	return "https://www.openstreetmap.org/?mlat=" + latText + "&mlon=" + lonText +
		"#map=17/" + latText + "/" + lonText
}

func coordText(lat, lon float64) string {
	return "Centroide: " + strconv.FormatFloat(lat, 'f', 6, 64) + ", " +
		strconv.FormatFloat(lon, 'f', 6, 64)
}

func formatRadius(metres int) string {
	if metres <= 0 {
		return "desconhecido"
	}
	if metres < 1000 {
		return strconv.Itoa(metres) + " m"
	}
	return strings.Replace(fmt.Sprintf("%.1f km", float64(metres)/1000), ".", ",", 1)
}

// ErrorMessage translates a failure from the cep.is client into a sentence in
// Portuguese that says what happened and what the user can do about it.
//
// Every branch is spelled out. A user who gets no answer assumes the bot is
// broken and stops using it, and "não encontrado" and "a API está fora" call
// for completely different reactions.
func ErrorMessage(err error) string {
	switch {
	case errors.Is(err, cepis.ErrCEPNotFound):
		return notFoundMessage(err)
	case errors.Is(err, cepis.ErrInvalidCEP):
		return "✋ CEP inválido. Preciso de oito dígitos: <code>01001000</code> " +
			"ou <code>01001-000</code>."
	case errors.Is(err, cepis.ErrRateLimited):
		return "🚦 A API está limitando as consultas neste momento. " +
			"Tente de novo em alguns instantes."
	case errors.Is(err, cepis.ErrServer):
		return "💥 A API da cep.is respondeu com erro. " +
			"Não é problema do seu CEP — tente de novo em alguns minutos."
	case errors.Is(err, cepis.ErrNetwork):
		return "🔌 Não consegui falar com a cep.is. " +
			"Pode ser instabilidade de rede — tente de novo em alguns minutos."
	case errors.Is(err, cepis.ErrInvalidResponse):
		return "🤔 A cep.is respondeu algo que não consegui interpretar. " +
			"Tente de novo em alguns minutos."
	}
	return "⚠️ Não consegui consultar este CEP agora. Tente de novo em alguns minutos."
}

// The two halves of the not-found answer, unchanged from the day the bot
// shipped. Whatever is said about the municipality goes between them: the reply
// opens by saying the CEP does not exist and closes by saying what to do, so
// the middle cannot be mistaken for an address.
const (
	notFoundHead   = "🔍 CEP não encontrado na base dos Correios (DNE)."
	notFoundAdvice = "Confira os oito dígitos — a base é atualizada a cada quinze dias."
)

// notFoundMessage answers a CEP that does not exist, naming the municipality it
// would belong to when the API told us which one.
//
// It is worth the extra lines. The CEP that fails is almost never a random
// number — it is someone who knows the city and guessed the rest, most often at
// the "-000" that 957 municipalities never received. Telling that person only
// "não encontrei" wastes the trip; telling them the number would have been in
// Areal/RJ says which half of their guess was right.
//
// What it must never do is read like a hit. There is no 📮, no address block
// and no CEP suggested from inside the range: the range is sparse — Areal's 118
// CEPs are spread over nearly five thousand numbers — so its ends are the
// extremes of what exists, not a list of what is valid, and the reply says so.
func notFoundMessage(err error) string {
	faixa := lookup.FaixaOf(err)
	if faixa == nil || faixa.Localidade == "" {
		return notFoundHead + "\n" + notFoundAdvice
	}

	var b strings.Builder
	b.WriteString(notFoundHead + "\n")
	b.WriteString("Ele cairia em <b>" + esc(faixa.Place()) + "</b>")

	count := faixaCount(faixa)
	span := faixaSpan(faixa)
	switch {
	case count != "" && span != "":
		b.WriteString(", que tem " + count + ", " + span + ".\n")
		b.WriteString("<i>A faixa é esparsa: nem todo número entre os dois é um CEP válido.</i>\n")
	case count != "":
		b.WriteString(", que tem " + count + ".\n")
	case span != "":
		b.WriteString(", com CEPs " + span + ".\n")
		b.WriteString("<i>A faixa é esparsa: nem todo número entre os dois é um CEP válido.</i>\n")
	default:
		b.WriteString(".\n")
	}

	b.WriteString(notFoundAdvice)
	return b.String()
}

// faixaCount renders how many CEPs the municipality has, or "" when the API did
// not say. Without it the two ends of the range read as a count of one big
// block, which is the misreading the number exists to prevent.
func faixaCount(faixa *lookup.Faixa) string {
	switch {
	case faixa.CEPs <= 0:
		return ""
	case faixa.CEPs == 1:
		return "1 CEP"
	}
	return strconv.Itoa(faixa.CEPs) + " CEPs"
}

// faixaSpan renders the ends of the range, or "" when they are missing or are
// the same number — "de X a X" is not a range, and printing a single CEP there
// would hand the user a guess to try.
func faixaSpan(faixa *lookup.Faixa) string {
	first, last := maskCEP(faixa.CEPIni), maskCEP(faixa.CEPFim)
	if first == "" || last == "" || first == last {
		return ""
	}
	return "de <code>" + esc(first) + "</code> a <code>" + esc(last) + "</code>"
}

// maskCEP puts the mask on eight digits, and returns "" for anything else: a
// CEP the API sent in a shape this bot does not recognise is left out of the
// sentence rather than printed raw.
func maskCEP(cep string) string {
	cep = strings.TrimSpace(cep)
	if len(cep) != 8 {
		return ""
	}
	for _, r := range cep {
		if r < '0' || r > '9' {
			return ""
		}
	}
	return cep[:5] + "-" + cep[5:]
}

// RateLimitMessage is what a user held by the local token bucket is told, once
// per warning window.
func RateLimitMessage(retryAfter time.Duration) string {
	seconds := int(retryAfter.Seconds())
	if seconds < 1 {
		seconds = 1
	}
	return "🐢 Calma — muitas consultas seguidas. Tente de novo em " +
		strconv.Itoa(seconds) + "s."
}

// HelpMessage explains the three ways to use the bot. The username comes from
// getMe, so the examples are copy-pasteable for whichever bot the operator
// created with @BotFather.
func HelpMessage(username string) string {
	at := "@" + username
	return "<b>cep.is</b> — consulta de CEP na base oficial dos Correios (DNE).\n\n" +
		"<b>Aqui no privado</b>\n" +
		"Mande o CEP e pronto: <code>01001000</code> ou <code>01001-000</code>.\n\n" +
		"<b>Em grupos e canais</b>\n" +
		"Use <code>/cep 01001000</code>. Se houver outros bots, " +
		"<code>/cep" + esc(at) + " 01001000</code> também funciona.\n\n" +
		"<b>Em qualquer conversa</b>\n" +
		"Digite <code>" + esc(at) + " 01001000</code> e escolha o resultado. " +
		"Não precisa me adicionar ao grupo.\n\n" +
		"Cerca de 57% dos CEPs têm coordenada. Quando o CEP é geral do " +
		"município, eu aviso em vez de mandar um pino no mapa.\n\n" +
		"API pública e documentação: https://cep.is"
}

// StartMessage is the answer to /start: a greeting plus the whole of
// [HelpMessage], because a new user pressing Start has no other instructions.
func StartMessage(username string) string {
	return "👋 Olá! Eu consulto CEP.\n\n" + HelpMessage(username)
}

// UsageMessage is the answer to a bare /cep with no argument.
func UsageMessage(username string) string {
	return "Use <code>/cep 01001000</code>.\n" +
		"Em qualquer conversa também dá para usar <code>@" + esc(username) +
		" 01001000</code>."
}

// UnknownMessage is the answer to text in a private chat that is not a CEP and
// not a command. It is only ever sent in private: answering unrecognised text
// in a group would make the bot a nuisance.
const UnknownMessage = "Não entendi. Mande um CEP (<code>01001000</code>) " +
	"ou use /help."

func esc(text string) string { return html.EscapeString(text) }