package main

import (
	"context"
	"encoding/json"
	"fmt"
	"log/slog"
	"net/http"
	"time"

	"github.com/jackc/pgx/v5"
	"github.com/jackc/pgx/v5/pgxpool"
)

// newPool creates a pgx pool. When readOnly (the default in parallel mode), every
// connection is forced into read-only transactions so the Go service can never
// mutate the production inventory_db it shares with the Python service.
func newPool(ctx context.Context, dsn string, readOnly bool) (*pgxpool.Pool, error) {
	cfg, err := pgxpool.ParseConfig(dsn)
	if err != nil {
		return nil, fmt.Errorf("parse DATABASE_URL: %w", err)
	}
	cfg.MaxConns = 10
	cfg.MaxConnIdleTime = 5 * time.Minute
	if readOnly {
		cfg.AfterConnect = func(ctx context.Context, conn *pgx.Conn) error {
			_, err := conn.Exec(ctx, "SET default_transaction_read_only = on")
			return err
		}
	}
	return pgxpool.NewWithConfig(ctx, cfg)
}

func queryRowsAsMaps(ctx context.Context, pool *pgxpool.Pool, sql string, args ...any) ([]map[string]any, error) {
	rows, err := pool.Query(ctx, sql, args...)
	if err != nil {
		return nil, err
	}
	out, err := pgx.CollectRows(rows, pgx.RowToMap)
	if err != nil {
		return nil, err
	}
	if out == nil {
		out = []map[string]any{}
	}
	return out, nil
}

// pyISO mirrors Python datetime.isoformat() for a UTC value (matches FastAPI's
// jsonable_encoder). Note the inventory-service stores naive datetimes (no tz),
// so isoformat has no offset — we format without one.
func pyISO(t time.Time) string {
	t = t.UTC()
	if t.Nanosecond() == 0 {
		return t.Format("2006-01-02T15:04:05")
	}
	return t.Format("2006-01-02T15:04:05") + fmt.Sprintf(".%06d", t.Nanosecond()/1000)
}

func formatTimes(rows []map[string]any, keys ...string) {
	for _, m := range rows {
		for _, k := range keys {
			if t, ok := m[k].(time.Time); ok {
				m[k] = pyISO(t)
			}
		}
	}
}

func toStr(v any) string {
	if s, ok := v.(string); ok {
		return s
	}
	return ""
}

func writeJSON(w http.ResponseWriter, status int, v any) {
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(status)
	if err := json.NewEncoder(w).Encode(v); err != nil {
		slog.Error("json encode failed", "err", err)
	}
}