// Package brief builds and sends the morning briefs through the house Apprise
// API (AGENTS.md §4 FR-9, FR-10, FR-12, FR-14, §11 Phase 7).
//
// One brief goes to each boy — what is on today, overdue work, pending work and
// the school notices — and one combined brief goes to Jo and Sam. Every
// delivery attempt is recorded in `notifications`, one row per recipient per
// channel, so a failed send is visible rather than silent (FR-12, FR-13).
//
// The service never holds a destination: it names an Apprise tag, for example
// "harry_email", and the Apprise configuration on `.35` holds the address
// (AGENTS.md §10 rule 3).
package brief

import (
	"context"
	"fmt"
	"log/slog"
	"sort"
	"strings"
	"time"

	"gitea.lab.audasmedia.com.au/sam/compass_teams_nhs/internal/apprise"
	"gitea.lab.audasmedia.com.au/sam/compass_teams_nhs/internal/config"
	"gitea.lab.audasmedia.com.au/sam/compass_teams_nhs/internal/dashboard"
	"gitea.lab.audasmedia.com.au/sam/compass_teams_nhs/internal/decode"
	"gitea.lab.audasmedia.com.au/sam/compass_teams_nhs/internal/store"
)

// ScopeCombined is the scope of the single brief to Jo and Sam.
const ScopeCombined = "combined"

// Service builds and delivers briefs. Every field is required except Log, which
// defaults to the standard logger.
type Service struct {
	Store  *store.Store
	Client *apprise.Client
	Cfg    config.AppriseConfig
	Loc    *time.Location
	Log    *slog.Logger
	// Now is injectable so tests can pin the clock.
	Now func() time.Time
}

// New builds a Service.
func New(st *store.Store, client *apprise.Client, cfg config.AppriseConfig, loc *time.Location, log *slog.Logger) *Service {
	if loc == nil {
		loc = time.UTC
	}
	if log == nil {
		log = slog.Default()
	}
	return &Service{Store: st, Client: client, Cfg: cfg, Loc: loc, Log: log, Now: time.Now}
}

// Delivery is one send attempt: one recipient, one channel, one Apprise tag.
type Delivery struct {
	Recipient string
	Channel   string
	Tag       string
	OK        bool
	Status    int
	Error     string
	// ID is the `notifications` row for this attempt.
	ID int64
}

// Send is one brief and everything that happened to it.
type Send struct {
	// Scope is the child name, or ScopeCombined.
	Scope string
	// Title is the message subject.
	Title string
	// Text is the brief itself.
	Text string
	// Recipients are the names the brief went to, in order.
	Recipients []string
	// Deliveries is one entry per recipient per channel.
	Deliveries []Delivery
	// ScanFailed lists the children whose last scan did not complete, so the
	// caller can exit loudly (FR-12).
	ScanFailed []string
}

// Failed is the number of delivery attempts that did not deliver.
func (s Send) Failed() int {
	n := 0
	for _, d := range s.Deliveries {
		if !d.OK {
			n++
		}
	}
	return n
}

// Delivered is the number of delivery attempts that delivered.
func (s Send) Delivered() int { return len(s.Deliveries) - s.Failed() }

// OK reports whether every attempt delivered and no scan was broken.
func (s Send) OK() bool { return s.Failed() == 0 && len(s.ScanFailed) == 0 }

// SentOK reports whether every delivery attempt delivered, ignoring the scan
// state (which is reported separately).
func (s Send) SentOK() bool { return s.Failed() == 0 }

// FirstError is the first redacted delivery error, or "" when nothing failed.
func (s Send) FirstError() string {
	for _, d := range s.Deliveries {
		if !d.OK {
			return d.Error
		}
	}
	return ""
}

// ChildrenText returns one child's brief and whether that child's last scan
// completed. A failed or missing scan never reads as "nothing due": the brief
// opens with an explicit warning (FR-12).
func (s *Service) ChildrenText(ctx context.Context, child store.Child) (string, bool, error) {
	items, err := s.Store.ItemsForChild(ctx, child.ID)
	if err != nil {
		return "", false, fmt.Errorf("items for %s: %w", child.Name, err)
	}
	buckets := dashboard.Classify(items, s.Now(), s.Loc)
	dec, err := s.decoder(ctx)
	if err != nil {
		return "", false, err
	}
	text := dashboard.RenderBrief(child.Name, buckets, dec, s.Loc)

	sc, err := s.Store.ScanSummaryForChild(ctx, child.ID)
	if err != nil {
		return "", false, fmt.Errorf("scan summary for %s: %w", child.Name, err)
	}
	notice := s.scanNotice(child.Name, sc)
	if notice == "" {
		return text, true, nil
	}
	return notice + "\n" + text, false, nil
}

// decoder loads the editable codes map and returns the label decoder the brief
// uses (FR-17). It decodes lesson periods and timetable events; an unknown code
// renders raw, never blank.
func (s *Service) decoder(ctx context.Context) (func(string) string, error) {
	codes, err := s.Store.Codes(ctx)
	if err != nil {
		return nil, fmt.Errorf("decode map: %w", err)
	}
	return func(title string) string { return decode.Label(title, codes) }, nil
}

// CombinedText returns the single brief for Jo and Sam — both boys in one
// message — and the children whose scan did not complete.
func (s *Service) CombinedText(ctx context.Context, children []store.Child) (string, []string, error) {
	// Finn's block first, then Harry's (FR-9). Enforce the order here, not only in
	// the send plan, so every caller — the email, the CLI preview, the dashboard
	// and the Hub — renders the combined brief in the same order as the email.
	children = OrderChildren(children)
	parts := make([]dashboard.CombinedBrief, 0, len(children))
	var failed []string
	var notices []string
	dec, err := s.decoder(ctx)
	if err != nil {
		return "", nil, err
	}
	for _, c := range children {
		items, err := s.Store.ItemsForChild(ctx, c.ID)
		if err != nil {
			return "", nil, fmt.Errorf("items for %s: %w", c.Name, err)
		}
		parts = append(parts, dashboard.CombinedBrief{
			Child:   c.Name,
			Buckets: dashboard.Classify(items, s.Now(), s.Loc),
		})
		sc, err := s.Store.ScanSummaryForChild(ctx, c.ID)
		if err != nil {
			return "", nil, fmt.Errorf("scan summary for %s: %w", c.Name, err)
		}
		if notice := s.scanNotice(c.Name, sc); notice != "" {
			notices = append(notices, notice)
			failed = append(failed, c.Name)
		}
	}
	text := dashboard.RenderCombinedBrief(parts, dec, s.Loc)
	if len(notices) > 0 {
		text = strings.Join(notices, "\n") + "\n\n" + text
	}
	return text, failed, nil
}

// scanNotice is the FR-12 warning for one child, or "" when the last scan
// completed.
func (s *Service) scanNotice(child string, sc store.ScanStatus) string {
	switch {
	case !sc.EverRun:
		return fmt.Sprintf("%s — BRIEF UNAVAILABLE: no scan has run yet. Due work is UNKNOWN, not “nothing due”.", child)
	case sc.Last != nil && !sc.Last.OK:
		detail := strings.TrimSpace(sc.Last.Error)
		when := sc.Last.StartedAt.In(s.Loc).Format("Mon 02 Jan 15:04")
		msg := fmt.Sprintf("%s — SCAN FAILED at %s", child, when)
		if detail != "" {
			msg += " (" + detail + ")"
		}
		return msg + ". Due work is UNKNOWN, not “nothing due”."
	default:
		return ""
	}
}

// RecipientsFor resolves names to configured Apprise recipients, and fails
// loudly when a name is not configured.
func (s *Service) RecipientsFor(names []string) ([]config.Recipient, error) {
	out := make([]config.Recipient, 0, len(names))
	for _, name := range names {
		r, ok := s.Cfg.RecipientByName(name)
		if !ok {
			return nil, fmt.Errorf("recipient %q is not configured (SCHOOL_APPRISE_TAGS)", name)
		}
		out = append(out, r)
	}
	return out, nil
}

// ChildRecipients returns the configured recipients that are children, matched
// by name against the children table.
func (s *Service) ChildRecipients(child store.Child) ([]config.Recipient, error) {
	return s.RecipientsFor([]string{child.Name})
}

// ParentRecipients returns the recipients of the combined brief (FR-14).
func (s *Service) ParentRecipients() ([]config.Recipient, string, error) {
	parents := s.Cfg.ParentRecipients()
	if len(parents) == 0 {
		return nil, "", fmt.Errorf("no parents configured for the combined brief (SCHOOL_APPRISE_PARENTS)")
	}
	names := make([]string, 0, len(parents))
	for _, p := range parents {
		names = append(names, p.Name)
	}
	return parents, strings.Join(names, "+"), nil
}

// Deliver sends one brief to the given recipients on the given channels and
// records every attempt. It never returns an error for a failed delivery: the
// failure is in the returned Send, recorded in the database, and the caller is
// responsible for going loud (FR-12).
func (s *Service) Deliver(ctx context.Context, scope, title, text string, recipients []config.Recipient, channels []string) (Send, error) {
	out := Send{Scope: scope, Title: title, Text: text}
	if len(recipients) == 0 {
		return out, fmt.Errorf("no recipients for scope %q", scope)
	}
	if len(channels) == 0 {
		return out, fmt.Errorf("no channels requested for scope %q", scope)
	}
	if s.Client == nil || !s.Client.Configured() {
		return out, fmt.Errorf("apprise is not configured: set %s",
			strings.Join(s.Cfg.Missing(), ", "))
	}

	now := s.Now()
	for _, r := range recipients {
		out.Recipients = append(out.Recipients, r.Name)
		for _, ch := range channels {
			tag := s.Cfg.ChannelTag(r, ch)
			d := Delivery{Recipient: r.Name, Channel: ch, Tag: tag}

			res, err := s.Client.SendTags(ctx, []string{tag}, title, text, apprise.TypeInfo)
			d.Status = res.Status
			d.OK = err == nil
			if err != nil {
				// apprise.Redact has already run on the response text, so no
				// address or phone number reaches the log or the row.
				d.Error = apprise.Truncate(err.Error(), 300)
			}
			sentAt := &now
			if !d.OK {
				sentAt = nil
			}
			id, recErr := s.Store.RecordNotification(ctx, store.Notification{
				Scope:     scope,
				Recipient: r.Name,
				Channel:   ch,
				Tag:       tag,
				Text:      text,
				OK:        d.OK,
				Error:     d.Error,
				SentAt:    sentAt,
			})
			if recErr != nil {
				return out, recErr
			}
			d.ID = id
			if d.OK {
				s.Log.Info("brief delivered", "scope", scope, "recipient", r.Name, "channel", ch, "tag", tag, "status", d.Status)
			} else {
				s.Log.Error("brief NOT delivered", "scope", scope, "recipient", r.Name, "channel", ch, "tag", tag, "status", d.Status, "err", d.Error)
			}
			out.Deliveries = append(out.Deliveries, d)
		}
	}
	return out, nil
}

// planned is one brief that is ready to go: the send, plus the resolved
// Apprise recipients it would go to.
type planned struct {
	Send
	recipients []config.Recipient
}

// Morning builds and sends the whole morning run: one brief per boy, then one
// combined brief to Jo and Sam (FR-9, FR-14). The briefs always go out, even
// when a scan failed, because the failure notice is the message that matters
// most; ScanFailed tells the caller to exit loudly.
func (s *Service) Morning(ctx context.Context, channels []string) ([]Send, error) {
	plans, err := s.plan(ctx)
	if err != nil {
		return nil, err
	}
	sends := make([]Send, 0, len(plans))
	for _, p := range plans {
		send, err := s.Deliver(ctx, p.Scope, p.Title, p.Text, p.recipients, channels)
		if err != nil {
			return sends, err
		}
		send.ScanFailed = p.ScanFailed
		sends = append(sends, send)
	}
	return sends, nil
}

// Plan builds every morning brief without sending anything. It is the build
// path Morning uses, exposed for the machine endpoint's dry run so the n8n
// wiring can be checked without messaging the family.
func (s *Service) Plan(ctx context.Context) ([]Send, error) {
	plans, err := s.plan(ctx)
	if err != nil {
		return nil, err
	}
	out := make([]Send, 0, len(plans))
	for _, p := range plans {
		out = append(out, p.Send)
	}
	return out, nil
}

// plan builds the per-boy briefs and the combined brief, without sending.
func (s *Service) plan(ctx context.Context) ([]planned, error) {
	children, err := s.Store.ListChildren(ctx)
	if err != nil {
		return nil, fmt.Errorf("list children: %w", err)
	}
	if len(children) == 0 {
		return nil, fmt.Errorf("no children on file: nothing to brief")
	}
	// Finn's block first, then Harry's: the required order (FR-9).
	children = OrderChildren(children)

	var out []planned
	for _, c := range children {
		text, scanOK, err := s.ChildrenText(ctx, c)
		if err != nil {
			return out, err
		}
		recipients, err := s.ChildRecipients(c)
		if err != nil {
			return out, err
		}
		p := planned{
			Send: Send{
				Scope:      c.Name,
				Title:      fmt.Sprintf("%s — school brief %s", c.Name, s.Now().In(s.Loc).Format("Mon 02 Jan")),
				Text:       text,
				Recipients: []string{c.Name},
			},
			recipients: recipients,
		}
		if !scanOK {
			p.ScanFailed = []string{c.Name}
		}
		out = append(out, p)
	}

	parents, _, err := s.ParentRecipients()
	if err != nil {
		return out, err
	}
	text, failed, err := s.CombinedText(ctx, children)
	if err != nil {
		return out, err
	}
	names := make([]string, 0, len(parents))
	for _, r := range parents {
		names = append(names, r.Name)
	}
	out = append(out, planned{
		Send: Send{
			Scope:      ScopeCombined,
			Title:      fmt.Sprintf("School brief — %s %s", combinedNames(children), s.Now().In(s.Loc).Format("Mon 02 Jan")),
			Text:       text,
			Recipients: names,
			ScanFailed: failed,
		},
		recipients: parents,
	})
	return out, nil
}

// OrderChildren returns the children in brief order: Finn's block first, then
// Harry's (FR-9). The order is by name, which puts Finn before Harry; it is
// shared by the send path and the dry-run build so both agree.
func OrderChildren(children []store.Child) []store.Child {
	out := append([]store.Child(nil), children...)
	sort.SliceStable(out, func(i, j int) bool { return out[i].Name < out[j].Name })
	return out
}

func combinedNames(children []store.Child) string {
	names := make([]string, 0, len(children))
	for _, c := range children {
		names = append(names, c.Name)
	}
	switch len(names) {
	case 0:
		return "school"
	case 1:
		return names[0]
	case 2:
		return names[0] + " and " + names[1]
	default:
		return strings.Join(names[:len(names)-1], ", ") + " and " + names[len(names)-1]
	}
}

// CombinedNames is the exported form of the display label for the combined
// brief, used by the Send panel.
func CombinedNames(children []store.Child) string { return combinedNames(children) }