package backthink

import (
	"context"
	"database/sql"
	"fmt"
	"log/slog"
	"time"

	"git.yeij.top/AskaEth/Cyrene_v2/internal/logger"
)

// defaultListLimit is the number of most-recent records returned by List when the
// caller passes a non-positive limit.
const defaultListLimit = 50

// DDL for the thinking record store. at/created_at follow the project timestamp
// convention (RFC3339 with a timezone); trigger and conclusion are the free-text
// fields the panel renders; the push_* columns carry a decomposed PushResult so
// List need not parse a blob. The primary key is the project-standard auto id.
const createRecordsSQL = `
CREATE TABLE IF NOT EXISTS backthink_records (
    id           INTEGER PRIMARY KEY AUTOINCREMENT,
    trigger      TEXT NOT NULL,
    at           TEXT NOT NULL,
    conclusion   TEXT NOT NULL,
    should_push  INTEGER NOT NULL,
    push_pushed  INTEGER NOT NULL DEFAULT 0,
    push_route   TEXT NOT NULL,
    push_detail  TEXT NOT NULL DEFAULT '',
    push_error   TEXT NOT NULL DEFAULT '',
    created_at   TEXT NOT NULL DEFAULT (strftime('%Y-%m-%dT%H:%M:%fZ','now'))
)`

const createRecordsIndexSQL = `
CREATE INDEX IF NOT EXISTS idx_backthink_records_at ON backthink_records(at)`

const insertRecordSQL = `
INSERT INTO backthink_records
    (trigger, at, conclusion, should_push, push_pushed, push_route, push_detail, push_error)
VALUES (?, ?, ?, ?, ?, ?, ?, ?)`

const selectRecordsSQL = `
SELECT id, trigger, at, conclusion, should_push, push_pushed, push_route, push_detail, push_error
FROM backthink_records
ORDER BY id DESC
LIMIT ?`

// Record is one persisted thinking pass (design/12 §4), returned by Store.List
// and the service's List. Trigger is the source subsystem label, At the decision
// timestamp, Conclusion the runtime's output, ShouldPush the interrupt decision
// and PushResult how (or whether) the push went out.
type Record struct {
	ID         int64
	Trigger    string
	At         time.Time
	Conclusion string
	ShouldPush bool
	PushResult PushResult
}

// Store persists thinking records in SQLite. It creates its table and index in
// NewStore so the module is self-contained (no migration bookkeeping), mirrors
// how channel/session creates its own table. It is concurrency-safe by virtue of
// the underlying *sql.DB.
type Store struct {
	db  *sql.DB
	log *slog.Logger
}

// NewStore builds a Store, ensuring the backthink_records table and index exist.
// It returns ErrNilDB when db is nil. ctx is used for the DDL.
func NewStore(ctx context.Context, db *sql.DB, log *slog.Logger) (*Store, error) {
	if db == nil {
		return nil, ErrNilDB
	}
	log = logger.WithSource(baseLog(log), "services/backthink")
	if _, err := db.ExecContext(ctx, createRecordsSQL); err != nil {
		return nil, fmt.Errorf("backthink: ensure backthink_records: %w", err)
	}
	if _, err := db.ExecContext(ctx, createRecordsIndexSQL); err != nil {
		return nil, fmt.Errorf("backthink: ensure backthink_records index: %w", err)
	}
	return &Store{db: db, log: log}, nil
}

// Append persists r and returns the new record id.
func (s *Store) Append(ctx context.Context, r Record) (int64, error) {
	res, err := s.db.ExecContext(ctx, insertRecordSQL,
		r.Trigger,
		r.At.UTC().Format(time.RFC3339Nano),
		r.Conclusion,
		boolInt(r.ShouldPush),
		boolInt(r.PushResult.Pushed),
		string(r.PushResult.Route),
		r.PushResult.Detail,
		r.PushResult.Err,
	)
	if err != nil {
		return 0, fmt.Errorf("backthink: insert record: %w", err)
	}
	id, err := res.LastInsertId()
	if err != nil {
		return 0, fmt.Errorf("backthink: record id: %w", err)
	}
	if s.log != nil {
		s.log.Debug("backthink record appended", "id", id, "trigger", r.Trigger, "should_push", r.ShouldPush, "route", r.PushResult.Route)
	}
	return id, nil
}

// List returns the most recent records newest-first. A non-positive limit selects
// defaultListLimit.
func (s *Store) List(ctx context.Context, limit int) ([]Record, error) {
	if limit <= 0 {
		limit = defaultListLimit
	}
	if err := ctx.Err(); err != nil {
		return nil, err
	}
	rows, err := s.db.QueryContext(ctx, selectRecordsSQL, limit)
	if err != nil {
		return nil, fmt.Errorf("backthink: list records: %w", err)
	}
	defer rows.Close()

	records := make([]Record, 0, limit)
	for rows.Next() {
		var (
			r          Record
			at         string
			route      string
			pushed     int
			shouldPush int
		)
		if err := rows.Scan(
			&r.ID,
			&r.Trigger,
			&at,
			&r.Conclusion,
			&shouldPush,
			&pushed,
			&route,
			&r.PushResult.Detail,
			&r.PushResult.Err,
		); err != nil {
			return nil, fmt.Errorf("backthink: scan record: %w", err)
		}
		r.ShouldPush = intBool(shouldPush)
		r.PushResult.Pushed = intBool(pushed)
		r.PushResult.Route = Route(route)
		r.At = parseTime(at)
		records = append(records, r)
	}
	if err := rows.Err(); err != nil {
		return nil, fmt.Errorf("backthink: iterate records: %w", err)
	}
	return records, nil
}

// boolInt maps a bool to the SQLite INTEGER 1/0 representation.
func boolInt(b bool) int {
	if b {
		return 1
	}
	return 0
}

// intBool maps a SQLite INTEGER to a bool.
func intBool(n int) bool { return n != 0 }

// parseTime parses a stored RFC3339(nano/with-zone) timestamp, falling back to
// the zero time so a malformed row never breaks a listing.
func parseTime(s string) time.Time {
	for _, layout := range []string{time.RFC3339Nano, time.RFC3339} {
		if t, err := time.Parse(layout, s); err == nil {
			return t
		}
	}
	return time.Time{}
}