package porkbun

import (
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	neturl "net/url"
	"strconv"
	"strings"
	"time"
)

const DefaultBaseURL = "https://api.porkbun.com/api/json/v3"

type Client struct {
	apiKey       string
	secretAPIKey string
	baseURL      string
	httpClient   *http.Client
}

type Option func(*Client)

func WithBaseURL(u string) Option {
	return func(c *Client) { c.baseURL = strings.TrimRight(u, "/") }
}

func WithHTTPClient(h *http.Client) Option {
	return func(c *Client) { c.httpClient = h }
}

func NewClient(apiKey, secretAPIKey string, opts ...Option) *Client {
	c := &Client{
		apiKey:       apiKey,
		secretAPIKey: secretAPIKey,
		baseURL:      DefaultBaseURL,
		httpClient:   &http.Client{Timeout: 30 * time.Second},
	}
	for _, opt := range opts {
		opt(c)
	}
	return c
}

type APIError struct {
	HTTPStatus int
	Status     string
	Message    string
}

func (e *APIError) Error() string {
	msg := e.Message
	if msg == "" {
		msg = "no error message returned"
	}
	return fmt.Sprintf("porkbun API error (HTTP %d, status %q): %s", e.HTTPStatus, e.Status, msg)
}

type Record struct {
	ID      string
	Name    string
	Type    string
	Content string
	TTL     int
	Prio    int
}

type RecordSpec struct {
	Name    string
	Type    string
	Content string
	TTL     int
	Prio    int
}

func (c *Client) Ping(ctx context.Context) (string, error) {
	var out struct {
		YourIP string `json:"yourIp"`
	}
	if err := c.post(ctx, "/ping", nil, &out); err != nil {
		return "", err
	}
	return out.YourIP, nil
}

func (c *Client) CreateRecord(ctx context.Context, domain string, spec RecordSpec) (string, error) {
	body := map[string]any{
		"name":    spec.Name,
		"type":    spec.Type,
		"content": spec.Content,
		// The API documents ttl and prio as strings.
		"ttl":  strconv.Itoa(spec.TTL),
		"prio": strconv.Itoa(spec.Prio),
	}
	var out struct {
		ID flexString `json:"id"`
	}
	if err := c.post(ctx, "/dns/create/"+url(domain), body, &out); err != nil {
		return "", err
	}
	if out.ID == "" {
		return "", fmt.Errorf("porkbun API reported success creating a record on %q but returned no record ID", domain)
	}
	return string(out.ID), nil
}

func (c *Client) EditRecord(ctx context.Context, domain, id string, spec RecordSpec) error {
	body := map[string]any{
		"type":    spec.Type,
		"content": spec.Content,
		"ttl":     strconv.Itoa(spec.TTL),
		"prio":    strconv.Itoa(spec.Prio),
	}
	return c.post(ctx, "/dns/edit/"+url(domain)+"/"+url(id), body, nil)
}

func (c *Client) DeleteRecord(ctx context.Context, domain, id string) error {
	return c.post(ctx, "/dns/delete/"+url(domain)+"/"+url(id), nil, nil)
}

func (c *Client) GetRecord(ctx context.Context, domain, id string) (*Record, error) {
	var out struct {
		Records []wireRecord `json:"records"`
	}
	if err := c.post(ctx, "/dns/retrieve/"+url(domain)+"/"+url(id), nil, &out); err != nil {
		return nil, err
	}
	if len(out.Records) == 0 {
		return nil, nil
	}
	rec := out.Records[0].toRecord()
	return &rec, nil
}

type wireRecord struct {
	ID      flexString `json:"id"`
	Name    string     `json:"name"`
	Type    string     `json:"type"`
	Content string     `json:"content"`
	TTL     flexInt    `json:"ttl"`
	Prio    flexInt    `json:"prio"`
}

func (w wireRecord) toRecord() Record {
	return Record{
		ID:      string(w.ID),
		Name:    w.Name,
		Type:    w.Type,
		Content: w.Content,
		TTL:     int(w.TTL),
		Prio:    int(w.Prio),
	}
}

type flexString string

func (f *flexString) UnmarshalJSON(b []byte) error {
	var s string
	if err := json.Unmarshal(b, &s); err == nil {
		*f = flexString(s)
		return nil
	}
	var n json.Number
	if err := json.Unmarshal(b, &n); err == nil {
		*f = flexString(n.String())
		return nil
	}
	return fmt.Errorf("expected string or number, got %s", b)
}

type flexInt int

func (f *flexInt) UnmarshalJSON(b []byte) error {
	if string(b) == "null" || string(b) == `""` {
		*f = 0
		return nil
	}
	var n int
	if err := json.Unmarshal(b, &n); err == nil {
		*f = flexInt(n)
		return nil
	}
	var s string
	if err := json.Unmarshal(b, &s); err == nil {
		v, err := strconv.Atoi(strings.TrimSpace(s))
		if err != nil {
			return fmt.Errorf("expected numeric string, got %q", s)
		}
		*f = flexInt(v)
		return nil
	}
	return fmt.Errorf("expected number or numeric string, got %s", b)
}

func url(segment string) string {
	return neturl.PathEscape(segment)
}

func (c *Client) post(ctx context.Context, path string, body map[string]any, out any) error {
	payload := map[string]any{
		"apikey":       c.apiKey,
		"secretapikey": c.secretAPIKey,
	}
	for k, v := range body {
		payload[k] = v
	}
	buf, err := json.Marshal(payload)
	if err != nil {
		return fmt.Errorf("encoding request for %s: %w", path, err)
	}

	req, err := http.NewRequestWithContext(ctx, http.MethodPost, c.baseURL+path, bytes.NewReader(buf))
	if err != nil {
		return fmt.Errorf("building request for %s: %w", path, err)
	}
	req.Header.Set("Content-Type", "application/json")

	resp, err := c.httpClient.Do(req)
	if err != nil {
		return fmt.Errorf("calling porkbun API %s: %w", path, err)
	}
	defer resp.Body.Close()

	raw, err := io.ReadAll(io.LimitReader(resp.Body, 1<<20))
	if err != nil {
		return fmt.Errorf("reading response from %s: %w", path, err)
	}

	var envelope struct {
		Status  string `json:"status"`
		Message string `json:"message"`
	}
	if err := json.Unmarshal(raw, &envelope); err != nil {
		return fmt.Errorf("porkbun API %s returned HTTP %d with an unparseable body: %w", path, resp.StatusCode, err)
	}
	if envelope.Status != "SUCCESS" {
		return &APIError{HTTPStatus: resp.StatusCode, Status: envelope.Status, Message: envelope.Message}
	}
	if out != nil {
		if err := json.Unmarshal(raw, out); err != nil {
			return fmt.Errorf("decoding response from %s: %w", path, err)
		}
	}
	return nil
}