package web

// The accounts and folder pages (novox/hq ADR 0440 §4, issue 1264): the accounts page lists every account
// mail-store.accounts answers, each with its state and its folders' mail and unread counts; the folder page
// lists one folder's mails, newest first, 50 a page, from mail-store.search, paged by the date of the last one
// shown. Every page behind the sign-in (NewServer's own RequireSession wrapping); rendered only through
// html/template, so nothing a mail carries is ever interpreted as markup.

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

// accountBucketValue and accountBucketFolder mirror mesh-mail's own AccountValue and AccountFolderValue
// (modules/mesh-mail/cmd/mesh-mail/mirror.go, issue 1255) — copied, not imported: mesh-mail-web is its own Go
// module, and the shape is mesh-mail's own to change. Only the fields this page reads are kept.
type accountBucketValue struct {
	State   string                `json:"state"`
	Folders []accountBucketFolder `json:"folders"`
}

type accountBucketFolder struct {
	Name   string `json:"name"`
	Mails  int    `json:"mails"`
	Unread int    `json:"unread"`
}

// accountsAnswer is mail-store.accounts' own answer (mesh-mail tools.go accountsTool), the fields this page
// reads.
type accountsAnswer struct {
	Accounts []struct {
		Account string `json:"account"`
		Kind    string `json:"kind"`
		Address string `json:"address"`
		State   string `json:"state"`
		Why     string `json:"why"`
	} `json:"accounts"`
}

// accountRow is one account's own line on the accounts page.
type accountRow struct {
	Name, Kind, Address, State, Why string
	FoldersKnown                    bool
	Folders                         []accountBucketFolder
}

// mailEntryRow is one mail entry as the mail-reading section shows it (novox/hq ADR 0459 §13, issue 1430):
// account, message id, date, sender name, subject, group, summary, mark, why and due date — never a body.
// Rendered only through html/template, so nothing a mail carries is ever interpreted as markup (AC1). ID is
// 1523's own: the correction form's hidden field.
type mailEntryRow struct {
	ID                                int64
	SenderName, Summary, Why, DueDate string // SenderName: SenderShown, its address when it has no name (1850)
}

// mailGroupRow is one mail group with how many entries hold it (1430/AC1).
type mailGroupRow struct {
	Label string
	Count int
}

// mailLessonRow is one reading lesson, with its own undo form (1523/AC2).
type mailLessonRow struct {
	ID                                int64
	SenderName, Subject, Change, Made string
	Undone                            bool
}

// weekRow is one week's reading-lessons-per-100-read-mails measure (1523/AC3).
type weekRow struct {
	WeekStart string
	Display   string // "N per 100" or "no mail was read this week"
}

// mailReadingData is what the accounts page shows above the classical list (1430/AC1-AC3, 1523/AC1-AC3):
// with Unavailable set (mail-reading did not answer status at all, 1430/AC3), nothing else here is shown.
// Otherwise, Healthy says whether to show Groups (healthy, 1430/AC1) or Cause and Since in their place
// (unhealthy, 1430/AC2); Matters and ScamWarnings are shown either way, each with its own correction form
// (1523/AC1); Lessons lists the reading lessons, each with its own undo form (1523/AC2); Weeks is the
// weekly measure (1523/AC3). TokenField is the signed-in session's own form token (1523/AC1, AC2), set by
// accountsPage itself — mailReadingSection knows nothing of the session.
type mailReadingData struct {
	Unavailable  string
	Healthy      bool
	Cause, Since string
	Matters      []mailEntryRow
	Groups       []mailGroupRow
	ScamWarnings []mailEntryRow
	Lessons      []mailLessonRow
	Weeks        []weekRow
	TokenField   template.HTML
}

var accountsTemplate = template.Must(template.New("accounts").Parse(`<!DOCTYPE html>
<html><head><title>Mail accounts</title></head><body>
<h1>Accounts</h1>
<section id="mail-reading">
{{with .MailReading}}
{{$mr := .}}
{{if .Unavailable}}<p>Mail reading is unavailable: {{.Unavailable}}</p>
{{else}}
<h2>Mail that matters</h2>
{{if .Matters}}<ul>{{range .Matters}}<li>{{.SenderName}} — {{.Summary}}{{if .DueDate}} — due {{.DueDate}}{{end}}{{if .Why}} ({{.Why}}){{end}}
<form method="post" action="/mail-correct">
<input type="hidden" name="id" value="{{.ID}}">
<select name="mark"><option value="">(keep mark)</option><option value="matters">matters</option><option value="scam warning">scam warning</option><option value="neither">neither</option></select>
<input type="text" name="group" placeholder="mail group">
{{$mr.TokenField}}
<button type="submit">Save</button>
</form>
</li>{{end}}</ul>
{{else}}<p>Nothing matters right now.</p>{{end}}
{{if .Healthy}}
<h2>Mail groups</h2>
{{if .Groups}}<ul>{{range .Groups}}<li>{{.Label}}: {{.Count}}</li>{{end}}</ul>{{else}}<p>No mail groups yet.</p>{{end}}
{{else}}
<h2>Mail reading</h2>
<p>Unhealthy: {{.Cause}} (since {{.Since}})</p>
{{end}}
<h2>Scam warnings</h2>
{{if .ScamWarnings}}<ul>{{range .ScamWarnings}}<li>{{.SenderName}} — {{.Summary}}{{if .Why}}: {{.Why}}{{end}}
<form method="post" action="/mail-correct">
<input type="hidden" name="id" value="{{.ID}}">
<select name="mark"><option value="">(keep mark)</option><option value="matters">matters</option><option value="scam warning">scam warning</option><option value="neither">neither</option></select>
<input type="text" name="group" placeholder="mail group">
{{$mr.TokenField}}
<button type="submit">Save</button>
</form>
</li>{{end}}</ul>
{{else}}<p>None.</p>{{end}}
<h2>Reading lessons</h2>
{{if .Lessons}}<ul>{{range .Lessons}}<li>{{.SenderName}} — {{.Subject}}: {{.Change}} ({{.Made}})
<form method="post" action="/mail-undo"><input type="hidden" name="id" value="{{.ID}}">{{$mr.TokenField}}<button type="submit">Undo</button></form>
</li>{{end}}</ul>
{{else}}<p>No reading lessons yet.</p>{{end}}
<h2>Reading lessons per 100 mails read</h2>
<ul>{{range .Weeks}}<li>{{.WeekStart}}: {{.Display}}</li>{{end}}</ul>
{{end}}
{{end}}
</section>
{{if .Error}}<p>{{.Error}}</p>{{else}}
<ul>
{{range .Accounts}}
{{$row := .}}
<li><strong>{{.Name}}</strong> ({{.Kind}}, {{.Address}}) — {{.State}}{{if .Why}}: {{.Why}}{{end}}
{{if .FoldersKnown}}
<ul>
{{range .Folders}}<li><a href="/folder?account={{$row.CurrentAccount}}&amp;folder={{.Name}}">{{.Name}}</a>: {{.Mails}} mail(s), {{.Unread}} unread</li>{{end}}
</ul>
{{else}}<p>its folders are not known yet</p>{{end}}
</li>
{{end}}
</ul>
{{end}}
</body></html>`))

// accountsTemplateData avoids the html/template range variable losing access to the account's own name inside
// its nested range over folders (Go templates have no closures): each row carries its own name twice.
type accountsTemplateData struct {
	MailReading mailReadingData
	Accounts    []accountRowWithName
	Error       string
}

type accountRowWithName struct {
	accountRow
	CurrentAccount string
}

// mailStatusAnswer, mailEntriesAnswer and mailGroupsAnswer are mail-reading's own status, entries and
// groups verbs' answer shapes (modules/mesh-mail-reader/cmd/mesh-mail-reader/tools.go entriesTool,
// groupsTool, statusTool), the fields this page reads — never a mail body.
type mailStatusAnswer struct {
	Healthy bool   `json:"healthy"`
	Cause   string `json:"cause"`
	Why     string `json:"why"`
	Since   string `json:"since"`
	// Weeks is 1523/AC3: the weekly reading-lessons-per-100-read-mails measure, as mail-reading.status
	// answers it (modules/mesh-mail-reader/cmd/mesh-mail-reader/tools.go statusTool).
	Weeks []struct {
		WeekStart     string   `json:"week-start"`
		LessonsPer100 *float64 `json:"lessons-per-100"`
		Why           string   `json:"why"`
	} `json:"weeks"`
}

type mailEntriesAnswer struct {
	Entries []struct {
		ID            int64  `json:"id"`
		SenderName    string `json:"sender-name"`
		SenderAddress string `json:"sender-address"`
		Subject       string `json:"subject"`
		Summary       string `json:"summary"`
		Mark          string `json:"mark"`
		Why           string `json:"why"`
		DueDate       string `json:"due-date"`
	} `json:"entries"`
}

type mailGroupsAnswer struct {
	Groups []struct {
		Label string `json:"label"`
		Count int    `json:"count"`
	} `json:"groups"`
}

// mailLessonsAnswer is mail-reading.lessons' own answer (1523/AC2).
type mailLessonsAnswer struct {
	Lessons []struct {
		ID            int64  `json:"id"`
		SenderName    string `json:"sender-name"`
		SenderAddress string `json:"sender-address"`
		Subject       string `json:"subject"`
		Change        string `json:"change"`
		Made          string `json:"made"`
		Undone        bool   `json:"undone"`
	} `json:"lessons"`
}

// mailReadingSection is 1430/AC1-AC3: asks mail-reading.status first; not answering or refusing at all makes
// the whole section say mail reading is unavailable and why (AC3), and nothing else here is asked. Otherwise
// entries and groups are asked too (healthy or not: the mail that matters and the scam warnings are shown
// either way, AC1, AC2); any later failure here falls back to the same "unavailable" message, since by then
// the operator has already been told the one reason that matters.
func (b *Bundle) mailReadingSection(ctx context.Context) mailReadingData {
	statusRaw, err := b.mailStatusAsk(ctx, map[string]any{})
	if err != nil {
		return mailReadingData{Unavailable: "mail-reading does not answer: " + err.Error()}
	}
	var status mailStatusAnswer
	if err := json.Unmarshal(statusRaw, &status); err != nil {
		return mailReadingData{Unavailable: "mail-reading's status could not be read"}
	}
	data := mailReadingData{Healthy: status.Healthy, Cause: status.Cause, Since: status.Since}

	entriesRaw, err := b.mailEntriesAsk(ctx, map[string]any{})
	if err != nil {
		return mailReadingData{Unavailable: "mail-reading does not answer: " + err.Error()}
	}
	var entries mailEntriesAnswer
	if err := json.Unmarshal(entriesRaw, &entries); err != nil {
		return mailReadingData{Unavailable: "mail-reading's entries could not be read"}
	}
	for _, e := range entries.Entries {
		row := mailEntryRow{ID: e.ID, SenderName: SenderShown(e.SenderName, e.SenderAddress), Summary: e.Summary, Why: e.Why, DueDate: e.DueDate}
		switch e.Mark {
		case "matters":
			data.Matters = append(data.Matters, row)
		case "scam warning":
			data.ScamWarnings = append(data.ScamWarnings, row)
		}
	}

	if status.Healthy {
		groupsRaw, err := b.mailGroupsAsk(ctx, map[string]any{})
		if err != nil {
			return mailReadingData{Unavailable: "mail-reading does not answer: " + err.Error()}
		}
		var groups mailGroupsAnswer
		if err := json.Unmarshal(groupsRaw, &groups); err != nil {
			return mailReadingData{Unavailable: "mail-reading's groups could not be read"}
		}
		for _, g := range groups.Groups {
			data.Groups = append(data.Groups, mailGroupRow{Label: g.Label, Count: g.Count})
		}
	}

	// 1523/AC2: the reading lessons, newest first (as mail-reading.lessons already answers them), each with
	// its own undo form.
	lessonsRaw, err := b.mailLessonsAsk(ctx, map[string]any{})
	if err != nil {
		return mailReadingData{Unavailable: "mail-reading does not answer: " + err.Error()}
	}
	var lessons mailLessonsAnswer
	if err := json.Unmarshal(lessonsRaw, &lessons); err != nil {
		return mailReadingData{Unavailable: "mail-reading's lessons could not be read"}
	}
	for _, l := range lessons.Lessons {
		data.Lessons = append(data.Lessons, mailLessonRow{
			ID: l.ID, SenderName: SenderShown(l.SenderName, l.SenderAddress), Subject: l.Subject, Change: l.Change, Made: l.Made, Undone: l.Undone,
		})
	}

	// 1523/AC3: the weekly measure, from status's own answer.
	for _, week := range status.Weeks {
		display := "no mail was read this week"
		if week.Why != "" {
			display = week.Why
		}
		if week.LessonsPer100 != nil {
			display = fmt.Sprintf("%.0f per 100", *week.LessonsPer100)
		}
		data.Weeks = append(data.Weeks, weekRow{WeekStart: week.WeekStart, Display: display})
	}
	return data
}

// accountsPage is issue 1264/AC1-AC5, 1430/AC1-AC3: lists every account mail-store.accounts answers (never
// one it did not, AC2), each with its folders' mail and unread counts read from mesh-mail's own account
// bucket — one Get per account mail-store answered, never Keys() (AC2), and never failing the whole page
// when an account has no key there yet (AC4); above it, what mail-reading shows (mailReadingSection, 1430).
// The classical list below always renders, even when mail-reading is unavailable (1430/AC3).
func (b *Bundle) accountsPage(w http.ResponseWriter, r *http.Request) {
	ctx, cancel := context.WithTimeout(r.Context(), 20*time.Second)
	defer cancel()
	mailReading := b.mailReadingSection(ctx)
	// 1523/AC1, AC2: the session's own form token, carried by every correction and undo form on this page.
	if sess, ok := SessionFrom(r); ok {
		mailReading.TokenField = FormTokenInput(sess)
	}
	raw, err := b.accountsAsk(ctx)
	if err != nil {
		renderPage(w, accountsTemplate, accountsTemplateData{MailReading: mailReading, Error: "mail-store does not answer; try again shortly"})
		return
	}
	var answer accountsAnswer
	if err := json.Unmarshal(raw, &answer); err != nil {
		renderPage(w, accountsTemplate, accountsTemplateData{MailReading: mailReading, Error: "mail-store's answer could not be read"})
		return
	}
	rows := make([]accountRowWithName, 0, len(answer.Accounts))
	for _, a := range answer.Accounts {
		row := accountRow{Name: a.Account, Kind: a.Kind, Address: a.Address, State: a.State, Why: a.Why}
		// 1264/AC2, AC4: read only this account's own key, never the bucket's whole list; a missing key (the
		// account's keeper has not mirrored it yet) is not an error, just "not known yet".
		entry, err := b.accountBucketGet(a.Account)
		if err == nil && entry != nil {
			var v accountBucketValue
			if json.Unmarshal(entry.Value, &v) == nil {
				row.Folders = v.Folders
				row.FoldersKnown = true
			}
		}
		rows = append(rows, accountRowWithName{accountRow: row, CurrentAccount: a.Account})
	}
	renderPage(w, accountsTemplate, accountsTemplateData{MailReading: mailReading, Accounts: rows})
}

// MostFolderResults is the folder and search pages' own page size (novox/hq ADR 0440 §4, issue 1264/AC3).
const MostFolderResults = 50

// searchResult is one mail as mail-store.search answers it (mesh-mail imap.go's metadata), the fields the
// folder and search pages read.
type searchResult struct {
	Account string         `json:"account"`
	Folder  string         `json:"folder"`
	UID     int            `json:"uid"`
	Date    string         `json:"date"`
	From    []personResult `json:"from"`
	To      []personResult `json:"to"`
	Subject string         `json:"subject"`
	Size    int64          `json:"size"`
	Flags   []string       `json:"flags"`
}

type personResult struct {
	Name    string `json:"name,omitempty"`
	Address string `json:"address"`
}

// searchAnswer is mail-store.search's own answer shape for a plain (non group-by-sender) search.
type searchAnswer struct {
	Found []searchResult `json:"found"`
}

var folderTemplate = template.Must(template.New("folder").Parse(`<!DOCTYPE html>
<html><head><title>{{.Folder}}</title></head><body>
<h1>{{.Account}} — {{.Folder}}</h1>
{{if .Error}}<p>{{.Error}}</p>{{else}}
<ul>
{{range .Mails}}<li>{{.Date}} — {{range .From}}{{.Name}} &lt;{{.Address}}&gt; {{end}}— <a href="/mail?account={{.Account}}&amp;folder={{.Folder}}&amp;uid={{.UID}}">{{.Subject}}</a></li>{{end}}
</ul>
{{if .NextBefore}}<p><a href="/folder?account={{.Account}}&amp;folder={{.Folder}}&amp;before={{.NextBefore}}">Older</a></p>{{end}}
{{end}}
</body></html>`))

type folderTemplateData struct {
	Account, Folder, NextBefore, Error string
	Mails                              []searchResult
}

// folderPage is issue 1264/AC3: the 50 newest mails of one folder, newest first, from mail-store.search; the
// next link asks for mails before the date of the 50th shown. A page with fewer than 50 has no next link: a
// mail sharing that exact second with the last one shown could be skipped by the next page (a known limit of
// paging by date alone, accepted rather than fixed here).
func (b *Bundle) folderPage(w http.ResponseWriter, r *http.Request) {
	account := r.URL.Query().Get("account")
	folder := r.URL.Query().Get("folder")
	before := r.URL.Query().Get("before")
	if account == "" || folder == "" {
		http.Error(w, "account and folder are both needed", http.StatusBadRequest)
		return
	}
	args := map[string]any{"account": account, "folder": folder, "limit": float64(MostFolderResults)}
	if before != "" {
		args["before"] = before
	}
	ctx, cancel := context.WithTimeout(r.Context(), 20*time.Second)
	defer cancel()
	raw, err := b.searchAsk(ctx, args)
	if err != nil {
		renderPage(w, folderTemplate, folderTemplateData{Account: account, Folder: folder, Error: "the folder could not be answered"})
		return
	}
	var answer searchAnswer
	if err := json.Unmarshal(raw, &answer); err != nil {
		renderPage(w, folderTemplate, folderTemplateData{Account: account, Folder: folder, Error: "the answer could not be read"})
		return
	}
	data := folderTemplateData{Account: account, Folder: folder, Mails: answer.Found}
	if len(answer.Found) >= MostFolderResults {
		data.NextBefore = answer.Found[len(answer.Found)-1].Date
	}
	renderPage(w, folderTemplate, data)
}

// renderPage executes tmpl, setting the page's own content type first; a template that fails to execute (it
// never should, given these fixed templates) says so in words, never a stack trace.
func renderPage(w http.ResponseWriter, tmpl *template.Template, data any) {
	w.Header().Set("Content-Type", "text/html; charset=utf-8")
	if err := tmpl.Execute(w, data); err != nil {
		fmt.Fprintf(w, "\n<!-- the page could not be rendered whole: %v -->", err)
	}
}