// queryd is the SQL execution layer. DuckDB engine (via cgo), reads
// Parquet directly from S3 via httpfs, registers catalog datasets as
// views, exposes POST /sql. The interesting glue is in
// internal/queryd/{db,registrar}.go; main.go wires the lifecycle.
package main

import (
	"context"
	"database/sql"
	"encoding/json"
	"errors"
	"flag"
	"log/slog"
	"net/http"
	"os"
	"strings"
	"time"

	"github.com/go-chi/chi/v5"

	"git.agentview.dev/profit/golangLAKEHOUSE/internal/catalogclient"
	"git.agentview.dev/profit/golangLAKEHOUSE/internal/queryd"
	"git.agentview.dev/profit/golangLAKEHOUSE/internal/secrets"
	"git.agentview.dev/profit/golangLAKEHOUSE/internal/shared"
)

const (
	primaryBucket   = "primary"
	maxSQLBodyBytes = 64 << 10 // 64 KiB cap on POST /sql body — SQL strings are not large
	defaultRefresh  = 30 * time.Second
)

func main() {
	configPath := flag.String("config", "lakehouse.toml", "path to TOML config")
	flag.Parse()

	cfg, err := shared.LoadConfig(*configPath)
	if err != nil {
		slog.Error("config", "err", err)
		os.Exit(1)
	}
	if cfg.Queryd.CatalogdURL == "" {
		slog.Error("config", "err", "queryd.catalogd_url is required")
		os.Exit(1)
	}
	if cfg.S3.Bucket == "" {
		slog.Error("config", "err", "s3.bucket is required")
		os.Exit(1)
	}

	refreshEvery := defaultRefresh
	if cfg.Queryd.RefreshEvery != "" {
		d, err := time.ParseDuration(cfg.Queryd.RefreshEvery)
		if err != nil {
			slog.Error("config", "err", "queryd.refresh_every is not a valid duration: "+err.Error())
			os.Exit(1)
		}
		refreshEvery = d
	}

	// Long-running ctx tied to lifetime of the process for the
	// background refresh goroutine. Cancelled when shared.Run returns.
	procCtx, procCancel := context.WithCancel(context.Background())
	defer procCancel()

	prov, err := secrets.NewFileProvider(cfg.Queryd.SecretsPath, secrets.S3Credentials{
		AccessKeyID:     cfg.S3.AccessKeyID,
		SecretAccessKey: cfg.S3.SecretAccessKey,
	})
	if err != nil {
		slog.Error("secrets", "err", err)
		os.Exit(1)
	}

	db, err := queryd.OpenDB(procCtx, cfg.S3, prov, primaryBucket)
	if err != nil {
		slog.Error("duckdb open", "err", err)
		os.Exit(1)
	}
	defer db.Close()

	catalog := catalogclient.New(cfg.Queryd.CatalogdURL)
	registrar := queryd.NewRegistrar(db, catalog, cfg.S3.Bucket)

	// Initial refresh — log if non-empty so the operator sees what
	// got loaded. A failure here is non-fatal: catalogd may be coming
	// up later in the boot order, the TTL goroutine will retry.
	refreshCtx, refreshCancel := context.WithTimeout(procCtx, 10*time.Second)
	stats, err := registrar.Refresh(refreshCtx)
	refreshCancel()
	if err != nil {
		slog.Warn("initial refresh failed (will retry)", "err", err)
	} else {
		slog.Info("initial refresh", "created", stats.Created, "skipped", stats.Skipped)
	}

	// Background ticker — drives Refresh on the configured interval.
	go runRefreshLoop(procCtx, registrar, refreshEvery)

	h := &handlers{db: db}

	if err := shared.Run("queryd", cfg.Queryd.Bind, h.register); err != nil {
		slog.Error("server", "err", err)
		os.Exit(1)
	}
}

// runRefreshLoop drives Registrar.Refresh on a ticker. Cancellable
// via ctx. Logs every refresh; in a quiet run that's chatty but
// useful for tracking when datasets land.
func runRefreshLoop(ctx context.Context, r *queryd.Registrar, every time.Duration) {
	ticker := time.NewTicker(every)
	defer ticker.Stop()
	for {
		select {
		case <-ctx.Done():
			return
		case <-ticker.C:
			rctx, cancel := context.WithTimeout(ctx, 10*time.Second)
			stats, err := r.Refresh(rctx)
			cancel()
			if err != nil {
				slog.Warn("refresh failed", "err", err)
				continue
			}
			if stats.Created+stats.Updated+stats.Dropped > 0 {
				slog.Info("refresh",
					"created", stats.Created,
					"updated", stats.Updated,
					"dropped", stats.Dropped,
					"skipped", stats.Skipped)
			}
		}
	}
}

type handlers struct {
	db *sql.DB
}

func (h *handlers) register(r chi.Router) {
	r.Post("/sql", h.handleSQL)
}

// sqlRequest is the POST /sql body shape.
type sqlRequest struct {
	SQL string `json:"sql"`
}

// sqlResponse is the result envelope. Columns + rows is the compact
// form; verbose row-as-object form is post-G0 if anyone needs it.
type sqlResponse struct {
	Columns  []sqlColumn `json:"columns"`
	Rows     [][]any     `json:"rows"`
	RowCount int         `json:"row_count"`
}

type sqlColumn struct {
	Name string `json:"name"`
	Type string `json:"type"`
}

func (h *handlers) handleSQL(w http.ResponseWriter, r *http.Request) {
	defer r.Body.Close()
	r.Body = http.MaxBytesReader(w, r.Body, maxSQLBodyBytes)
	var req sqlRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		var maxErr *http.MaxBytesError
		if errors.As(err, &maxErr) || strings.Contains(err.Error(), "http: request body too large") {
			http.Error(w, "sql body too large", http.StatusRequestEntityTooLarge)
			return
		}
		http.Error(w, "decode body: "+err.Error(), http.StatusBadRequest)
		return
	}
	if strings.TrimSpace(req.SQL) == "" {
		http.Error(w, "sql is empty", http.StatusBadRequest)
		return
	}

	rows, err := h.db.QueryContext(r.Context(), req.SQL)
	if err != nil {
		// DuckDB errors are user-facing for ad-hoc SQL — expose them
		// at 400 so callers can see what went wrong (table not found,
		// syntax error, etc.). Internal infra issues would surface as
		// 500 once we distinguish them later.
		http.Error(w, "query: "+err.Error(), http.StatusBadRequest)
		return
	}
	defer rows.Close()

	cols, err := rows.Columns()
	if err != nil {
		http.Error(w, "columns: "+err.Error(), http.StatusInternalServerError)
		return
	}
	colTypes, err := rows.ColumnTypes()
	if err != nil {
		http.Error(w, "column types: "+err.Error(), http.StatusInternalServerError)
		return
	}

	resp := sqlResponse{
		Columns: make([]sqlColumn, len(cols)),
		Rows:    [][]any{},
	}
	for i, name := range cols {
		resp.Columns[i] = sqlColumn{Name: name, Type: colTypes[i].DatabaseTypeName()}
	}

	for rows.Next() {
		dest := make([]any, len(cols))
		ptrs := make([]any, len(cols))
		for i := range dest {
			ptrs[i] = &dest[i]
		}
		if err := rows.Scan(ptrs...); err != nil {
			http.Error(w, "scan: "+err.Error(), http.StatusInternalServerError)
			return
		}
		// JSON can't encode []byte as text by default — DuckDB returns
		// VARCHAR as []byte through database/sql. Convert here.
		for i, v := range dest {
			if b, ok := v.([]byte); ok {
				dest[i] = string(b)
			}
		}
		resp.Rows = append(resp.Rows, dest)
	}
	if err := rows.Err(); err != nil {
		http.Error(w, "rows err: "+err.Error(), http.StatusInternalServerError)
		return
	}
	resp.RowCount = len(resp.Rows)

	w.Header().Set("Content-Type", "application/json")
	if err := json.NewEncoder(w).Encode(resp); err != nil {
		// Headers already sent — can't change the status code, but log
		// so an unsupported DuckDB column type (Decimal, INTERVAL, etc.)
		// surfaces in the operator log. Per scrum JSON-ERR (Opus).
		slog.Warn("sql encode response", "err", err)
	}
}