package web

// The write page and a send's state (novox/hq ADR 0440 §6, issue 1267): the form offers only the accounts
// mail-store.accounts answers; its POST (behind issue 1284's own per-session token, wired in here as this
// form's hidden field) calls mail-store.send, which raises the operator's Approve on Telegram and sends
// nothing itself, then shows the send's state from mail-store.send-status — in words, refreshing itself every
// 5 seconds with no script (a meta refresh) until a final state (sent, failed, refused, not proven, declined,
// expired, unknown; novox/hq ADR 0436 §12, issue 1261).

import (
	"context"
	"encoding/json"
	"html/template"
	"net/http"
	"net/url"
	"strings"
	"time"
)

// SendStatusRefreshEvery is how often the state page asks again while a send is still waiting (ADR 0440 §6).
const SendStatusRefreshEvery = 5

var writeTemplate = template.Must(template.New("write").Parse(`<!DOCTYPE html>
<html><head><title>Write mail</title></head><body>
<h1>Write</h1>
{{if .Error}}<p>{{.Error}}</p>{{else}}
<form method="post" action="/send">
<select name="account">{{range .Accounts}}<option value="{{.}}">{{.}}</option>{{end}}</select>
<input type="text" name="to" placeholder="to">
<input type="text" name="subject" placeholder="subject">
<textarea name="body"></textarea>
{{.TokenField}}
<button type="submit">Send</button>
</form>
{{end}}
</body></html>`))

type writeTemplateData struct {
	Accounts   []string
	TokenField template.HTML
	Error      string
}

var sendStatusTemplate = template.Must(template.New("send-status").Parse(`<!DOCTYPE html>
<html><head><title>Send</title>{{if .Refresh}}<meta http-equiv="refresh" content="{{.RefreshSeconds}}; url={{.RefreshURL}}">{{end}}</head>
<body>
{{if .Note}}<p>{{.Note}}</p>{{end}}
<p>{{.Words}}</p>
</body></html>`))

type sendStatusData struct {
	Note, Words, RefreshURL string
	RefreshSeconds          int
	Refresh                 bool
}

// grantedAccountNames is mail-store.accounts' own answer, read as the list of account names it granted —
// shared by the write page (issue 1267/AC1) and the send handler (AC4).
func (b *Bundle) grantedAccountNames(ctx context.Context) ([]string, error) {
	raw, err := b.accountsAsk(ctx)
	if err != nil {
		return nil, err
	}
	var answer accountsAnswer
	if err := json.Unmarshal(raw, &answer); err != nil {
		return nil, err
	}
	names := make([]string, 0, len(answer.Accounts))
	for _, a := range answer.Accounts {
		names = append(names, a.Account)
	}
	return names, nil
}

func containsName(names []string, name string) bool {
	for _, n := range names {
		if n == name {
			return true
		}
	}
	return false
}

// splitAddresses is the write form's own "to" field (one text input) split into mail-store.send's own array
// argument, on whitespace or commas.
func splitAddresses(s string) []string {
	var out []string
	for _, part := range strings.FieldsFunc(s, func(r rune) bool { return r == ',' || r == ' ' || r == '\n' }) {
		if part != "" {
			out = append(out, part)
		}
	}
	return out
}

// writePage is issue 1267/AC1: offers exactly the accounts mail-store.accounts answers, and (issue 1284) the
// signed-in session's own form token as a hidden field, so the POST below can tell this session's own form
// from any other's.
func (b *Bundle) writePage(w http.ResponseWriter, r *http.Request) {
	data := writeTemplateData{}
	if sess, ok := SessionFrom(r); ok {
		data.TokenField = FormTokenInput(sess)
	}
	ctx, cancel := context.WithTimeout(r.Context(), 20*time.Second)
	defer cancel()
	names, err := b.grantedAccountNames(ctx)
	if err != nil {
		data.Error = "the granted accounts could not be answered"
	} else {
		data.Accounts = names
	}
	renderPage(w, writeTemplate, data)
}

// sendHandler is issue 1267/AC2, AC4: called only once RequireFormToken (issue 1284) has already let the POST
// through. An account mail-store did not answer sends nothing (AC4); otherwise mail-store.send is called with
// exactly account, to, subject and body, and the answer is the send's own state page, noting that the
// operator's Approve is asked on Telegram (AC2).
func (b *Bundle) sendHandler(w http.ResponseWriter, r *http.Request) {
	if err := r.ParseForm(); err != nil {
		http.Error(w, "bad request", http.StatusBadRequest)
		return
	}
	account := r.PostFormValue("account")
	to := r.PostFormValue("to")
	subject := r.PostFormValue("subject")
	body := r.PostFormValue("body")

	ctx, cancel := context.WithTimeout(r.Context(), 20*time.Second)
	defer cancel()
	granted, err := b.grantedAccountNames(ctx)
	if err != nil || !containsName(granted, account) {
		renderPage(w, sendStatusTemplate, sendStatusData{Words: "the account is not granted"})
		return
	}
	raw, err := b.sendAsk(ctx, map[string]any{
		"account": account, "to": splitAddresses(to), "subject": subject, "body": body,
	})
	if err != nil {
		renderPage(w, sendStatusTemplate, sendStatusData{Words: "the send could not be asked"})
		return
	}
	var answer struct {
		Ask string `json:"ask"`
	}
	_ = json.Unmarshal(raw, &answer)
	b.renderSendStatus(w, answer.Ask, "The operator's Approve is asked on Telegram.")
}

// sendStatusPage is GET /send-status?id=...: the send's own state page, polled by its own meta refresh (issue
// 1267/AC3) until a final state.
func (b *Bundle) sendStatusPage(w http.ResponseWriter, r *http.Request) {
	b.renderSendStatus(w, r.URL.Query().Get("id"), "")
}

// renderSendStatus is issue 1267/AC3: the send's state in words from mail-store.send-status; "waiting" (not
// yet final) refreshes itself every SendStatusRefreshEvery seconds with a meta refresh, no script; every
// other state (sent, failed, refused, not proven, declined, expired, unknown) is final and does not refresh.
func (b *Bundle) renderSendStatus(w http.ResponseWriter, id, note string) {
	ctx, cancel := context.WithTimeout(context.Background(), 20*time.Second)
	defer cancel()
	data := sendStatusData{Note: note}
	raw, err := b.sendStatusAsk(ctx, map[string]any{"id": id})
	if err != nil {
		data.Words = "the send's state could not be answered"
		renderPage(w, sendStatusTemplate, data)
		return
	}
	var answer struct {
		Status string `json:"status"`
		Words  string `json:"words"`
	}
	_ = json.Unmarshal(raw, &answer)
	data.Words = answer.Status
	if answer.Words != "" {
		data.Words += ": " + answer.Words
	}
	if answer.Status == "waiting" {
		data.Refresh = true
		data.RefreshSeconds = SendStatusRefreshEvery
		data.RefreshURL = "/send-status?id=" + url.QueryEscape(id)
	}
	renderPage(w, sendStatusTemplate, data)
}