package store

import (
	"context"
	"database/sql"
	"errors"
	"fmt"

	"gitea.stevedudenhoeffer.com/steve/pansy/internal/domain"
)

// journalColumns lists journal_entries columns in the order scanJournalEntry
// expects. Used unqualified for direct selects; the list read qualifies with j.
const journalColumns = `id, garden_id, object_id, planting_id, author_id, body,
	observed_at, version, created_at, updated_at`

// journalScanTargets returns the scan destinations for journalColumns, in order.
// The list read appends one more for the joined author name, so the two readers
// share a single definition of the column order rather than each repeating it.
func journalScanTargets(e *domain.JournalEntry) []any {
	return []any{
		&e.ID, &e.GardenID, &e.ObjectID, &e.PlantingID, &e.AuthorID, &e.Body,
		&e.ObservedAt, &e.Version, &e.CreatedAt, &e.UpdatedAt,
	}
}

func scanJournalEntry(s scanner) (*domain.JournalEntry, error) {
	var e domain.JournalEntry
	if err := s.Scan(journalScanTargets(&e)...); err != nil {
		return nil, err
	}
	return &e, nil
}

// JournalFilter narrows a garden's journal. A nil field means "don't filter on
// this". ObjectID/PlantingID select entries about one bed or one plop; the date
// range is inclusive and matches observed_at, not created_at.
type JournalFilter struct {
	ObjectID   *int64
	PlantingID *int64
	From       *string
	To         *string
	Limit      int
	Offset     int
}

// CreateJournalEntry inserts an entry (fields already validated by the service).
func (d *DB) CreateJournalEntry(ctx context.Context, e *domain.JournalEntry) (*domain.JournalEntry, error) {
	created, err := scanJournalEntry(d.sql.QueryRowContext(ctx,
		`INSERT INTO journal_entries (garden_id, object_id, planting_id, author_id, body, observed_at)
		 VALUES (?, ?, ?, ?, ?, ?)
		 RETURNING `+journalColumns,
		e.GardenID, e.ObjectID, e.PlantingID, e.AuthorID, e.Body, e.ObservedAt,
	))
	if err != nil {
		return nil, fmt.Errorf("store: insert journal entry: %w", err)
	}
	return created, nil
}

// GetJournalEntry returns an entry by id, or domain.ErrNotFound. Permission is
// the service's business, via the entry's garden.
func (d *DB) GetJournalEntry(ctx context.Context, id int64) (*domain.JournalEntry, error) {
	e, err := scanJournalEntry(d.sql.QueryRowContext(ctx,
		`SELECT `+journalColumns+` FROM journal_entries WHERE id = ?`, id))
	if errors.Is(err, sql.ErrNoRows) {
		return nil, domain.ErrNotFound
	}
	if err != nil {
		return nil, fmt.Errorf("store: get journal entry: %w", err)
	}
	return e, nil
}

// ListJournalEntries returns a garden's entries, most recently OBSERVED first,
// narrowed by the filter. Each carries its author's display name, so the list
// renders without a lookup per row. Always a non-nil slice.
func (d *DB) ListJournalEntries(ctx context.Context, gardenID int64, f JournalFilter) ([]domain.JournalEntry, error) {
	query := `SELECT ` + qualifyColumns("j", journalColumns) + `, u.display_name
		   FROM journal_entries j
		   JOIN users u ON u.id = j.author_id
		  WHERE j.garden_id = ?`
	args := []any{gardenID}

	if f.ObjectID != nil {
		query += ` AND j.object_id = ?`
		args = append(args, *f.ObjectID)
	}
	if f.PlantingID != nil {
		query += ` AND j.planting_id = ?`
		args = append(args, *f.PlantingID)
	}
	if f.From != nil {
		query += ` AND j.observed_at >= ?`
		args = append(args, *f.From)
	}
	if f.To != nil {
		query += ` AND j.observed_at <= ?`
		args = append(args, *f.To)
	}
	// id DESC breaks ties within a day, so several entries observed on the same
	// date still read newest-first rather than in arbitrary order.
	query += ` ORDER BY j.observed_at DESC, j.id DESC LIMIT ? OFFSET ?`
	args = append(args, f.Limit, f.Offset)

	rows, err := d.sql.QueryContext(ctx, query, args...)
	if err != nil {
		return nil, fmt.Errorf("store: list journal entries: %w", err)
	}
	defer rows.Close()

	entries := []domain.JournalEntry{}
	for rows.Next() {
		var e domain.JournalEntry
		if err := rows.Scan(append(journalScanTargets(&e), &e.AuthorName)...); err != nil {
			return nil, fmt.Errorf("store: scan journal entry: %w", err)
		}
		entries = append(entries, e)
	}
	if err := rows.Err(); err != nil {
		return nil, fmt.Errorf("store: iterate journal entries: %w", err)
	}
	return entries, nil
}

// JournalCounts returns how many entries a garden holds, keyed by the object
// they are about — key 0 for entries about the garden itself.
//
// A count per object rather than a flag, and one query rather than one per bed:
// the indicator has to be available when the journal panel is closed, which is
// exactly when nothing else has loaded the entries.
func (d *DB) JournalCounts(ctx context.Context, gardenID int64) (map[int64]int, error) {
	rows, err := d.sql.QueryContext(ctx,
		`SELECT COALESCE(object_id, 0), COUNT(*)
		   FROM journal_entries WHERE garden_id = ?
		  GROUP BY COALESCE(object_id, 0)`,
		gardenID)
	if err != nil {
		return nil, fmt.Errorf("store: journal counts: %w", err)
	}
	defer rows.Close()

	counts := map[int64]int{}
	for rows.Next() {
		var objectID int64
		var n int
		if err := rows.Scan(&objectID, &n); err != nil {
			return nil, fmt.Errorf("store: scan journal count: %w", err)
		}
		counts[objectID] = n
	}
	if err := rows.Err(); err != nil {
		return nil, fmt.Errorf("store: iterate journal counts: %w", err)
	}
	return counts, nil
}

// UpdateJournalEntry applies a version-guarded update of the mutable columns.
// Same contract as every other mutable resource. The target (garden/object/
// planting) and the author are immutable: an entry is a record of an observation,
// so re-pointing it at a different bed would be rewriting the observation rather
// than correcting the text.
func (d *DB) UpdateJournalEntry(ctx context.Context, e *domain.JournalEntry) (*domain.JournalEntry, error) {
	updated, err := scanJournalEntry(d.sql.QueryRowContext(ctx,
		`UPDATE journal_entries
		    SET body = ?, observed_at = ?,
		        version = version + 1,
		        updated_at = strftime('%Y-%m-%dT%H:%M:%SZ', 'now')
		  WHERE id = ? AND version = ?
		  RETURNING `+journalColumns,
		e.Body, e.ObservedAt, e.ID, e.Version,
	))
	if errors.Is(err, sql.ErrNoRows) {
		current, gerr := d.GetJournalEntry(ctx, e.ID)
		if gerr != nil {
			return nil, gerr
		}
		return current, domain.ErrVersionConflict
	}
	if err != nil {
		return nil, fmt.Errorf("store: update journal entry: %w", err)
	}
	return updated, nil
}

// DeleteJournalEntry removes an entry. Returns domain.ErrNotFound if none was.
func (d *DB) DeleteJournalEntry(ctx context.Context, id int64) error {
	res, err := d.sql.ExecContext(ctx, `DELETE FROM journal_entries WHERE id = ?`, id)
	if err != nil {
		return fmt.Errorf("store: delete journal entry: %w", err)
	}
	n, err := res.RowsAffected()
	if err != nil {
		return fmt.Errorf("store: journal delete rows: %w", err)
	}
	if n == 0 {
		return domain.ErrNotFound
	}
	return nil
}