package cepis

import (
	"encoding/json"
	"strconv"
)

// Geo is the CEP's coordinate, when the database has one.
//
// The point is the median of the coordinates of that CEP's addresses, not the
// mean: one badly geocoded address 40 km away shifts a mean and does not move
// a median.
//
// Always check Precisao before using Lat/Lon for distance:
//
//   - "logradouro": the point is a stretch of street. RaioM lands around
//     100–150 m. Good for maps and for distance.
//   - "localidade": the CEP is the whole municipality (a city-wide general
//     CEP), and the point is its centroid. RaioM runs from 7 km to 40 km.
//     Computing shipping from this is wrong by tens of kilometres.
//
// RaioM is the radius, in metres, containing 90% of that CEP's addresses. It
// exists precisely so that error cannot pass unnoticed.
type Geo struct {
	Lat      float64 `json:"lat"`
	Lon      float64 `json:"lon"`
	RaioM    int     `json:"raio_m"`
	Precisao string  `json:"precisao"`
}

// IsPrecise reports whether the coordinate points at a street rather than at a
// whole municipality. Shorthand for Precisao == "logradouro", which is the
// check to make before using the point to measure distance.
func (g Geo) IsPrecise() bool {
	return g.Precisao == "logradouro"
}

// Faixa is the municipality a CEP that does not exist would belong to, and the
// range of CEPs that municipality actually has. It arrives on the 404, hanging
// off [Error.Faixa].
//
// A CEP that fails is rarely a random number. It is usually someone who knows
// the city and guessed the rest, and the classic guess is the "-000": a small
// town often has a single city-wide CEP ending that way, but 957 municipalities
// are coded street by street and never got one. Areal/RJ answers from
// 25845-001 up, never at 25845-000 — so the 404 for 25845000 names Areal.
//
// CEPIni and CEPFim are the smallest and the largest CEP that EXIST in that
// municipality, not the bounds the Correios publish. Do not read the pair as a
// list of valid CEPs: the range is sparse, which is what CEPs is for — Areal's
// 118 CEPs are scattered across nearly five thousand numbers.
type Faixa struct {
	Localidade string `json:"localidade"`
	UF         string `json:"uf"`
	Estado     string `json:"estado"`
	Regiao     string `json:"regiao"`
	IBGE       string `json:"ibge"`
	CEPIni     string `json:"cep_ini"`
	CEPFim     string `json:"cep_fim"`

	// CEPs is how many CEPs the municipality actually has inside the range.
	CEPs int `json:"ceps"`
}

// Address is a CEP and everything the database knows about it.
//
// The field names are the API's own, in Portuguese, with only the casing
// adapted to Go: what you read in the JSON at https://cep.is/01001000 is what
// you access here. The values are Portuguese either way — they come from the
// Correios database.
//
// Fields the database does not have for that CEP come back as empty strings,
// never null. Geo is the exception: it is nil when there is no coordinate,
// because the API omits the whole object in that case (about 43% of CEPs)
// rather than sending null.
//
// Raw holds the response exactly as it arrived, uninterpreted, so a field the
// API grows before this library is updated is not lost.
type Address struct {
	CEP         string `json:"cep"`
	Logradouro  string `json:"logradouro"`
	Complemento string `json:"complemento"`
	Unidade     string `json:"unidade"`
	Bairro      string `json:"bairro"`
	Localidade  string `json:"localidade"`
	UF          string `json:"uf"`
	Estado      string `json:"estado"`
	Regiao      string `json:"regiao"`
	IBGE        string `json:"ibge"`
	GIA         string `json:"gia"`
	DDD         string `json:"ddd"`
	Siafi       string `json:"siafi"`
	Geo         *Geo   `json:"geo,omitempty"`

	// Raw is the response as it arrived, field by field, including fields
	// this version of the library does not know about.
	Raw map[string]json.RawMessage `json:"-"`
}

// FormattedCEP returns the CEP with its mask: "01001-000".
//
// The API always returns it unmasked; formatting is presentation, and it lives
// here so it does not become a repeated Sprintf in every project.
func (a *Address) FormattedCEP() string {
	if len(a.CEP) != 8 {
		return a.CEP
	}
	return a.CEP[:5] + "-" + a.CEP[5:]
}

// Field returns a field of the raw response as a string, "" when the API did
// not send it. Use it to read a field the API grew after this library was
// released, without waiting for a new version.
func (a *Address) Field(name string) string {
	if a.Raw == nil {
		return ""
	}
	return rawString(a.Raw[name])
}

// UnmarshalJSON decodes the API's JSON leniently.
//
// Unknown fields are ignored during decoding but preserved in Raw, so a new
// field in the API cannot break this library. A malformed geo block yields a
// nil Geo rather than failing the whole document: the rest of the address is
// still useful and it is not worth losing over a coordinate.
func (a *Address) UnmarshalJSON(data []byte) error {
	var raw map[string]json.RawMessage
	if err := json.Unmarshal(data, &raw); err != nil {
		return err
	}

	*a = Address{
		CEP:         rawString(raw["cep"]),
		Logradouro:  rawString(raw["logradouro"]),
		Complemento: rawString(raw["complemento"]),
		Unidade:     rawString(raw["unidade"]),
		Bairro:      rawString(raw["bairro"]),
		Localidade:  rawString(raw["localidade"]),
		UF:          rawString(raw["uf"]),
		Estado:      rawString(raw["estado"]),
		Regiao:      rawString(raw["regiao"]),
		IBGE:        rawString(raw["ibge"]),
		GIA:         rawString(raw["gia"]),
		DDD:         rawString(raw["ddd"]),
		Siafi:       rawString(raw["siafi"]),
		Geo:         decodeGeo(raw["geo"]),
		Raw:         raw,
	}
	return nil
}

func decodeGeo(block json.RawMessage) *Geo {
	if len(block) == 0 {
		return nil
	}
	var probe struct {
		Lat      *float64 `json:"lat"`
		Lon      *float64 `json:"lon"`
		RaioM    *int     `json:"raio_m"`
		Precisao *string  `json:"precisao"`
	}
	if err := json.Unmarshal(block, &probe); err != nil {
		return nil
	}
	if probe.Lat == nil || probe.Lon == nil || probe.RaioM == nil || probe.Precisao == nil {
		return nil
	}
	return &Geo{
		Lat:      *probe.Lat,
		Lon:      *probe.Lon,
		RaioM:    *probe.RaioM,
		Precisao: *probe.Precisao,
	}
}

// decodeFaixa reads the `faixa` block of a 404 body. Every failure — absent
// block, malformed JSON, a `faixa` without a locality — yields nil: the field
// is an extra on top of an error that is already complete without it, and it
// must never turn a clean ErrCEPNotFound into a parse failure.
func decodeFaixa(body []byte) *Faixa {
	if len(body) == 0 {
		return nil
	}
	var envelope struct {
		Faixa *Faixa `json:"faixa"`
	}
	if err := json.Unmarshal(body, &envelope); err != nil {
		return nil
	}
	if envelope.Faixa == nil || envelope.Faixa.Localidade == "" {
		return nil
	}
	return envelope.Faixa
}

func rawString(value json.RawMessage) string {
	if len(value) == 0 {
		return ""
	}
	var text string
	if err := json.Unmarshal(value, &text); err == nil {
		return text
	}
	var number json.Number
	if err := json.Unmarshal(value, &number); err == nil {
		return number.String()
	}
	return ""
}

// Health is the answer of GET /health.
//
// Good for two things: checking that the API answers, and knowing which
// version of the database is live. The DNE database changes every two weeks;
// DNE identifies it.
type Health struct {
	Status       string `json:"status"`
	DNE          string `json:"dne"`
	CEPs         int64  `json:"ceps"`
	Geo          int64  `json:"geo"`
	BaseGeradaEm string `json:"base_gerada_em"`

	// Raw is the response as it arrived, field by field.
	Raw map[string]json.RawMessage `json:"-"`
}

// OK reports whether the API describes itself as healthy.
func (h *Health) OK() bool {
	return h.Status == "ok"
}

// UnmarshalJSON decodes the health payload leniently, keeping the response in
// Raw and tolerating fields this version does not know about.
func (h *Health) UnmarshalJSON(data []byte) error {
	var raw map[string]json.RawMessage
	if err := json.Unmarshal(data, &raw); err != nil {
		return err
	}
	*h = Health{
		Status:       rawString(raw["status"]),
		DNE:          rawString(raw["dne"]),
		CEPs:         rawInt(raw["ceps"]),
		Geo:          rawInt(raw["geo"]),
		BaseGeradaEm: rawString(raw["base_gerada_em"]),
		Raw:          raw,
	}
	return nil
}

func rawInt(value json.RawMessage) int64 {
	text := rawString(value)
	if text == "" {
		return 0
	}
	number, err := strconv.ParseFloat(text, 64)
	if err != nil {
		return 0
	}
	return int64(number)
}