package main

// The reader's own index (novox/hq ADR 0459 §4): mail entries, mail groups and reading lessons for the verbs
// (1521, 1428), the waiting mails heard but not yet read (1518) and the reader's own health state (1519), each
// over postgres (pgstore.go) or in memory for the tests. Nothing here keeps a mail body or text taken from one.

import (
	"context"
	"time"
)

// Person is a sender, as mesh-mail's own event names one (name and address, never a body).
type Person struct {
	Name    string `json:"name,omitempty"`
	Address string `json:"address"`
}

// Mark is an entry's mark (novox/hq ADR 0459 §7).
type Mark string

const (
	MarkMatters     Mark = "matters"
	MarkScamWarning Mark = "scam warning"
	MarkNeither     Mark = "neither"
)

// Entry is one mail entry (ADR 0459 §4): the mail's own headers (never its body), the mail group it was
// batched into, a one-line summary, a mark and why, a due date, and whether it was told on the mail signal.
type Entry struct {
	ID            int64
	Account       string
	MessageID     string
	Folder        string
	Date          time.Time
	SenderName    string
	SenderAddress string
	Subject       string
	Group         int64 // the mail group's id, 0 when ungrouped
	Summary       string
	Mark          Mark // "" until a batch judges it
	Why           string
	DueDate       time.Time // zero when none
	Told          bool
	// Judged is when a batch judged this mail (issue 1520) — the week the weekly measure (1521/AC3) counts it
	// in, which is never the mail's own Date: a mail that arrived long before it was judged is read this week.
	Judged time.Time
}

// Group is one mail group (ADR 0459 §4). Count, how many entries hold it, is answered by Store.Groups
// (1521/AC2) and is never itself kept.
type Group struct {
	ID      int64
	Label   string
	Created time.Time
	Count   int
}

// Lesson is one reading lesson (ADR 0459 §8, §9): the corrected mail's own headers (sender name and address,
// subject, account and folder — never its body), the change made, when, and whether it was undone (1428/AC3).
// SenderAddress is the lesson's own matching key for the next batch's question (1427/AC1: "sender ... meets a
// mail of the batch"); Group, when not zero, is a second matching key for a mail already known to be of that
// group (the same clause's "or mail group") — no issue yet looks up a mail's group before it is judged, so in
// practice only SenderAddress matching fires today (1427's own tests); the field and the comparison both exist
// so that lookup can be added later without reshaping this type.
type Lesson struct {
	ID            int64
	Account       string
	Folder        string
	SenderName    string
	SenderAddress string
	Subject       string
	Group         int64 // 0 when the correction did not carry a mail group
	Change        string
	Made          time.Time
	Undone        bool
}

// WaitingMail is one mail heard (an added event) but not yet handed to reading (ADR 0459 §3, §12, issue 1518):
// headers only, never a body. Seq is the order it was heard in — a monotonic sequence, independent of Date —
// so catch-up after an outage reads in arrival order (1518/AC4), including mail heard while reading was
// unhealthy.
type WaitingMail struct {
	Seq         int64
	Account     string
	Folder      string
	MessageID   string
	UIDValidity uint32
	UID         uint32
	Date        time.Time
	From        []Person
	Subject     string
	Flags       []string
	Size        int64
	Heard       time.Time
}

// Key is the waiting mail's own identity: its message id wherever it has one (stable across a UIDVALIDITY
// reset), else its account, folder, UIDVALIDITY and UID (novox/hq ADR 0459 §3; the same fallback mesh-mail's
// own event dedupe, mesh-mail-notifier's EventBody.Handle, uses).
func (w WaitingMail) Key() string {
	if w.MessageID != "" {
		return w.Account + "\x1f" + w.MessageID
	}
	return w.Account + "\x1f" + w.Folder
}

// HealthOutcome names why a batch's judgement did not succeed (novox/hq ADR 0459 §12); the empty outcome means
// it succeeded.
type HealthOutcome string

const (
	OutcomeOK         HealthOutcome = ""
	OutcomeRefused    HealthOutcome = "refused"
	OutcomeTimedOut   HealthOutcome = "timed out"
	OutcomeOutOfShape HealthOutcome = "out of shape"
)

// ReaderHealth is the kept health state (1519): unhealthy once a judgement is refused, times out or answers out
// of shape, naming the cause, the judgement's own words, and since when; healthy again once one succeeds. Kept
// in the module's own database, so a restart answers the same (1519/AC4).
type ReaderHealth struct {
	Healthy bool
	Cause   HealthOutcome // "" while healthy
	Why     string        // the judgement's own words
	Since   time.Time     // the first failure's own time; zero while healthy
}

// Store is everything mesh-mail-reader keeps of its own. A PgStore (pgstore.go) backs it in the running
// module; the tests use an in-memory double (kit_test.go).
type Store interface {
	// AddWaiting records an added event as a waiting mail before the event is acknowledged (1518/AC2): a mail
	// heard is never lost, even if the module crashes before it is read. The same mail heard twice (1518/AC3,
	// matched by WaitingMail.Key) is recorded once; AddWaiting itself never errors on a duplicate.
	AddWaiting(ctx context.Context, w WaitingMail) error
	// Waiting answers every waiting mail in arrival order, oldest first (1518/AC4).
	Waiting(ctx context.Context) ([]WaitingMail, error)
	// TakeWaiting removes a waiting mail once it has been handed to reading (1520).
	TakeWaiting(ctx context.Context, seq int64) error

	// ReaderHealth answers the kept health state (1519/AC4); healthy with a zero Since on a fresh database.
	ReaderHealth(ctx context.Context) (ReaderHealth, error)
	// SetReaderHealth replaces the kept health state.
	SetReaderHealth(ctx context.Context, h ReaderHealth) error

	// AddEntry records a new mail entry (1520/AC3) and answers its own id.
	AddEntry(ctx context.Context, e Entry) (int64, error)
	// UpdateEntry replaces an entry's fields by its id (1428/AC1, correct). ErrNotFound when unknown.
	UpdateEntry(ctx context.Context, e Entry) error
	// Entry answers one entry by id, and whether it was found (1428/AC1, AC5: an unknown id is refused).
	Entry(ctx context.Context, id int64) (Entry, bool, error)
	// Entries answers every mail entry; ordering and filtering for the verb are 1521's own pure functions, not
	// the store's.
	Entries(ctx context.Context) ([]Entry, error)

	// FindOrCreateGroup answers the mail group of this label, making one if none yet carries it (1520/AC3): the
	// judge names groups by their label, never by id.
	FindOrCreateGroup(ctx context.Context, label string) (Group, error)
	// Groups answers every mail group, each with how many entries hold it (1521/AC2).
	Groups(ctx context.Context) ([]Group, error)

	// AddLesson keeps one reading lesson at once (1428/AC1) and answers its own id.
	AddLesson(ctx context.Context, l Lesson) (int64, error)
	// Lessons answers every reading lesson, undone ones included (1427's own selection, and 1428's lessons
	// verb, each decide for themselves what to do with Undone).
	Lessons(ctx context.Context) ([]Lesson, error)
	// UndoLesson marks one reading lesson undone (1428/AC3). ErrNotFound when unknown.
	UndoLesson(ctx context.Context, id int64) error
}

// ErrNotFound is answered by a Store method asked for something it does not hold.
var ErrNotFound = notFoundError{}

type notFoundError struct{}

func (notFoundError) Error() string { return "not found" }