package extsvc

import (
	"context"
	"fmt"
	"io"
	"net/http"
	"net/url"
	"regexp"
	"strconv"
	"strings"
	"time"
)

// eqslImportURL is eQSL.cc's ADIF import endpoint. It accepts a form-encoded
// POST (or URL params) with the account credentials and the ADIF content.
const eqslImportURL = "https://www.eQSL.cc/qslcard/ImportADIF.cfm"

// eqslResultRe extracts "Result: X out of Y records added" from the reply.
var eqslResultRe = regexp.MustCompile(`(?i)result:\s*(\d+)\s+out of\s+(\d+)\s+records added`)

// eqslPost performs the import POST and returns the raw response body. eQSL
// replies HTTP 200 with a plain-text/HTML body for both success and errors;
// callers classify it via the markers below.
func eqslPost(ctx context.Context, client *http.Client, user, pswd, adif string) (string, error) {
	form := url.Values{}
	form.Set("EQSL_USER", user)
	form.Set("EQSL_PSWD", pswd)
	form.Set("ADIFData", adif)

	req, err := http.NewRequestWithContext(ctx, http.MethodPost, eqslImportURL, strings.NewReader(form.Encode()))
	if err != nil {
		return "", fmt.Errorf("eqsl: build request: %w", err)
	}
	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")

	if client == nil {
		client = &http.Client{Timeout: 30 * time.Second}
	}
	resp, err := client.Do(req)
	if err != nil {
		return "", fmt.Errorf("eqsl: request failed: %w", err)
	}
	defer resp.Body.Close()
	body, _ := io.ReadAll(io.LimitReader(resp.Body, 256*1024))
	msg := strings.TrimSpace(string(body))
	if resp.StatusCode != http.StatusOK {
		if msg == "" {
			msg = fmt.Sprintf("HTTP %d", resp.StatusCode)
		}
		return msg, fmt.Errorf("eqsl: http %d: %s", resp.StatusCode, msg)
	}
	return msg, nil
}

// authErrEQSL returns a reason when the response signals bad credentials, else
// "". eQSL replies "Error: No match on eQSL_User/eQSL_Pswd".
func authErrEQSL(body string) string {
	if strings.Contains(strings.ToLower(body), "no match on eqsl") {
		return "invalid username or password"
	}
	return ""
}

// eqslRecordWithNickname prepends the APP_EQSL_QTH_NICKNAME tag to an ADIF
// record when nick is set, so eQSL files the QSO under the right QTH profile
// (required when the account has more than one). ADIF field order is free, so
// prepending before the rest of the record is valid.
func eqslRecordWithNickname(record, nick string) string {
	nick = strings.TrimSpace(nick)
	if nick == "" {
		return record
	}
	return fmt.Sprintf("<APP_EQSL_QTH_NICKNAME:%d>%s%s", len(nick), nick, record)
}

// UploadEQSL pushes one ADIF record to eQSL.cc for the given account. qthNick
// is the optional eQSL QTH nickname.
//
// eQSL replies with text: "Result: 1 out of 1 records added" on success,
// "Bad record: Duplicate" for an already-present QSO (treated as success so
// retries are idempotent), or "Error: No match on eQSL_User/eQSL_Pswd" for bad
// credentials.
func UploadEQSL(ctx context.Context, client *http.Client, user, pswd, qthNick, adifRecord string) (UploadResult, error) {
	user = strings.ToUpper(strings.TrimSpace(user))
	if user == "" {
		return UploadResult{}, fmt.Errorf("eqsl: username (callsign) not set")
	}
	if strings.TrimSpace(pswd) == "" {
		return UploadResult{}, fmt.Errorf("eqsl: password not set")
	}
	if strings.TrimSpace(adifRecord) == "" {
		return UploadResult{}, fmt.Errorf("eqsl: empty adif record")
	}

	body, err := eqslPost(ctx, client, user, pswd, eqslRecordWithNickname(adifRecord, qthNick))
	if err != nil {
		return UploadResult{OK: false, Message: body}, err
	}

	b := strings.ToLower(body)
	if reason := authErrEQSL(body); reason != "" {
		return UploadResult{OK: false, Message: reason}, fmt.Errorf("eqsl: %s", reason)
	}
	if strings.Contains(b, "duplicate") {
		return UploadResult{OK: true, Message: "already in logbook"}, nil
	}
	if m := eqslResultRe.FindStringSubmatch(body); m != nil {
		added, _ := strconv.Atoi(m[1])
		if added >= 1 {
			return UploadResult{OK: true, Message: strings.TrimSpace(m[0])}, nil
		}
		// "0 out of N" — eQSL accepted nothing; surface why if it said so.
		reason := eqslReason(body)
		return UploadResult{OK: false, Message: reason}, fmt.Errorf("eqsl: upload failed: %s", reason)
	}
	reason := eqslReason(body)
	return UploadResult{OK: false, Message: reason}, fmt.Errorf("eqsl: upload failed: %s", reason)
}

// eqslReason trims an eQSL reply to a short human-readable reason: the first
// "Error:" / "Warning:" / "Bad record:" line if present, else the whole body
// (capped), else a generic phrase.
func eqslReason(body string) string {
	for _, line := range strings.Split(body, "\n") {
		l := strings.TrimSpace(line)
		ll := strings.ToLower(l)
		if strings.HasPrefix(ll, "error:") || strings.HasPrefix(ll, "warning:") || strings.Contains(ll, "bad record") {
			return l
		}
	}
	b := strings.TrimSpace(body)
	if b == "" {
		return "upload rejected"
	}
	if len(b) > 200 {
		b = b[:200]
	}
	return b
}

// TestEQSL validates the configured eQSL credentials with a REAL request: it
// posts an empty ADIF so nothing is inserted, then checks for the bad-login
// marker. Anything else means the credentials were accepted.
func TestEQSL(ctx context.Context, client *http.Client, cfg ServiceConfig) (string, error) {
	user := strings.ToUpper(strings.TrimSpace(cfg.Username))
	if user == "" {
		return "", fmt.Errorf("eqsl: username (callsign) not set")
	}
	if strings.TrimSpace(cfg.Password) == "" {
		return "", fmt.Errorf("eqsl: password not set")
	}
	body, err := eqslPost(ctx, client, user, cfg.Password, "")
	if err != nil {
		return "", err
	}
	if reason := authErrEQSL(body); reason != "" {
		return "", fmt.Errorf("eqsl: %s", reason)
	}
	return fmt.Sprintf("Credentials accepted — %s", user), nil
}