package store

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

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

// The instance_settings row is seeded by migration 0010 and there is exactly one
// (CHECK id = 1), so reads never branch on existence and writes never insert.

const instanceSettingsColumns = `agent_model, agent_enabled, vision_model, version, updated_at`

// scanInstanceSettings reads the single settings row. agent_enabled is a nullable
// INTEGER (NULL = inherit env), so it is scanned through sql.NullInt64.
func scanInstanceSettings(s scanner) (*domain.InstanceSettings, error) {
	var (
		out     domain.InstanceSettings
		enabled sql.NullInt64
	)
	if err := s.Scan(&out.AgentModel, &enabled, &out.VisionModel, &out.Version, &out.UpdatedAt); err != nil {
		return nil, err
	}
	if enabled.Valid {
		b := enabled.Int64 != 0
		out.AgentEnabled = &b
	}
	return &out, nil
}

// GetInstanceSettings returns the single settings row.
func (d *DB) GetInstanceSettings(ctx context.Context) (*domain.InstanceSettings, error) {
	s, err := scanInstanceSettings(d.sql.QueryRowContext(ctx,
		`SELECT `+instanceSettingsColumns+` FROM instance_settings WHERE id = 1`))
	if errors.Is(err, sql.ErrNoRows) {
		// The migration seeds this row, so its absence is a broken database, not a
		// normal "not found" the caller should paper over.
		return nil, fmt.Errorf("store: instance_settings row missing (migration 0010 not applied?)")
	}
	if err != nil {
		return nil, fmt.Errorf("store: get instance settings: %w", err)
	}
	return s, nil
}

// UpdateInstanceSettings applies a version-guarded update to the single row,
// following the same optimistic-concurrency contract as every mutable resource:
// the updated row on success, (current row, ErrVersionConflict) on a version
// mismatch. There is no ErrNotFound path — the row always exists.
//
// agentEnabled is nil to store SQL NULL (inherit env), or a pointer to store an
// explicit 0/1.
func (d *DB) UpdateInstanceSettings(ctx context.Context, s *domain.InstanceSettings) (*domain.InstanceSettings, error) {
	var enabled any
	if s.AgentEnabled != nil {
		enabled = boolToInt(*s.AgentEnabled)
	}
	updated, err := scanInstanceSettings(d.sql.QueryRowContext(ctx,
		`UPDATE instance_settings
		    SET agent_model = ?, agent_enabled = ?, vision_model = ?,
		        version = version + 1,
		        updated_at = strftime('%Y-%m-%dT%H:%M:%SZ', 'now')
		  WHERE id = 1 AND version = ?
		  RETURNING `+instanceSettingsColumns,
		s.AgentModel, enabled, s.VisionModel, s.Version,
	))
	if errors.Is(err, sql.ErrNoRows) {
		current, gerr := d.GetInstanceSettings(ctx)
		if gerr != nil {
			return nil, gerr
		}
		return current, domain.ErrVersionConflict
	}
	if err != nil {
		return nil, fmt.Errorf("store: update instance settings: %w", err)
	}
	return updated, nil
}