package main

// REST handlers (read-only) for data_factory.db (issue 0097).
//
// Endpoints:
//   GET /api/datafactory/nodes?kind=<kind>
//   GET /api/datafactory/runs?node_id=<id>&limit=N
//   GET /api/datafactory/databases
//
// All endpoints lazy-open data_factory.db on first request (creating the
// file + applying migrations if missing). If the open fails, returns 503.
// POST trigger is intentionally NOT implemented — sqlite_api is read-only;
// run insertion is done out-of-band by DAG steps / function wrappers.

import (
	"context"
	"database/sql"
	"encoding/json"
	"fmt"
	"net/http"
	"os"
	"os/exec"
	"path/filepath"
	"regexp"
	"strconv"
)

// dataFactoryNode is the JSON row for /api/datafactory/nodes.
type dataFactoryNode struct {
	ID           string `json:"id"`
	Kind         string `json:"kind"`
	Name         string `json:"name"`
	FunctionID   string `json:"function_id"`
	Description  string `json:"description"`
	ConfigJSON   string `json:"config_json"`
	ScheduleCron string `json:"schedule_cron"`
	Enabled      bool   `json:"enabled"`
	TagsCSV      string `json:"tags_csv"`
	CreatedAt    string `json:"created_at"`
	UpdatedAt    string `json:"updated_at"`
}

// dataFactoryRun is the JSON row for /api/datafactory/runs.
type dataFactoryRun struct {
	ID         string `json:"id"`
	NodeID     string `json:"node_id"`
	StartedAt  string `json:"started_at"`
	FinishedAt string `json:"finished_at"`
	Status     string `json:"status"`
	RowsIn     int64  `json:"rows_in"`
	RowsOut    int64  `json:"rows_out"`
	KbIn       int64  `json:"kb_in"`
	KbOut      int64  `json:"kb_out"`
	DurationMS int64  `json:"duration_ms"`
	Trigger    string `json:"trigger"`
	Error      string `json:"error"`
	Notes      string `json:"notes"`
	StorageDBID  string `json:"storage_db_id"`
	StorageTable string `json:"storage_table"`
}

// dataFactoryDatabase is the JSON row for /api/datafactory/databases.
type dataFactoryDatabase struct {
	ID          string `json:"id"`
	Kind        string `json:"kind"`
	Label       string `json:"label"`
	URI         string `json:"uri"`
	Description string `json:"description"`
	TagsCSV     string `json:"tags_csv"`
	LastSeenAt  string `json:"last_seen_at"`
	TableCount  int64  `json:"table_count"`
	SizeBytes   int64  `json:"size_bytes"`
	CreatedAt   string `json:"created_at"`
	UpdatedAt   string `json:"updated_at"`
}

func (s *Server) handleDataFactoryNodes(w http.ResponseWriter, r *http.Request) {
	db, err := s.dataFactoryDB()
	if err != nil {
		writeError(w, http.StatusServiceUnavailable, "data_factory.db unavailable: "+err.Error())
		return
	}

	ctx, cancel := context.WithTimeout(r.Context(), queryTimeout)
	defer cancel()

	kind := r.URL.Query().Get("kind")
	var rows *sql.Rows
	if kind != "" {
		rows, err = db.QueryContext(ctx, `
			SELECT id, kind, name, function_id, description, config_json,
			       schedule_cron, enabled, tags_csv, created_at, updated_at
			FROM nodes
			WHERE kind = ?
			ORDER BY kind, name`, kind)
	} else {
		rows, err = db.QueryContext(ctx, `
			SELECT id, kind, name, function_id, description, config_json,
			       schedule_cron, enabled, tags_csv, created_at, updated_at
			FROM nodes
			ORDER BY kind, name`)
	}
	if err != nil {
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}
	defer rows.Close()

	nodes := make([]dataFactoryNode, 0, 16)
	for rows.Next() {
		var n dataFactoryNode
		var enabled int
		if err := rows.Scan(&n.ID, &n.Kind, &n.Name, &n.FunctionID, &n.Description,
			&n.ConfigJSON, &n.ScheduleCron, &enabled, &n.TagsCSV,
			&n.CreatedAt, &n.UpdatedAt); err != nil {
			writeError(w, http.StatusInternalServerError, err.Error())
			return
		}
		n.Enabled = enabled != 0
		nodes = append(nodes, n)
	}
	writeJSON(w, http.StatusOK, map[string]any{"nodes": nodes, "count": len(nodes)})
}

func (s *Server) handleDataFactoryRuns(w http.ResponseWriter, r *http.Request) {
	db, err := s.dataFactoryDB()
	if err != nil {
		writeError(w, http.StatusServiceUnavailable, "data_factory.db unavailable: "+err.Error())
		return
	}

	ctx, cancel := context.WithTimeout(r.Context(), queryTimeout)
	defer cancel()

	nodeID := r.URL.Query().Get("node_id")
	limit := 100
	if l := r.URL.Query().Get("limit"); l != "" {
		if n, err := strconv.Atoi(l); err == nil && n > 0 && n <= 1000 {
			limit = n
		}
	}

	var rows *sql.Rows
	if nodeID != "" {
		rows, err = db.QueryContext(ctx, `
			SELECT id, node_id, started_at, COALESCE(finished_at,''), status,
			       rows_in, rows_out, kb_in, kb_out, duration_ms, trigger, error, notes,
			       COALESCE(storage_db_id,''), COALESCE(storage_table,'')
			FROM runs
			WHERE node_id = ?
			ORDER BY started_at DESC
			LIMIT ?`, nodeID, limit)
	} else {
		rows, err = db.QueryContext(ctx, `
			SELECT id, node_id, started_at, COALESCE(finished_at,''), status,
			       rows_in, rows_out, kb_in, kb_out, duration_ms, trigger, error, notes,
			       COALESCE(storage_db_id,''), COALESCE(storage_table,'')
			FROM runs
			ORDER BY started_at DESC
			LIMIT ?`, limit)
	}
	if err != nil {
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}
	defer rows.Close()

	runs := make([]dataFactoryRun, 0, 16)
	for rows.Next() {
		var rr dataFactoryRun
		if err := rows.Scan(&rr.ID, &rr.NodeID, &rr.StartedAt, &rr.FinishedAt,
			&rr.Status, &rr.RowsIn, &rr.RowsOut, &rr.KbIn, &rr.KbOut,
			&rr.DurationMS, &rr.Trigger, &rr.Error, &rr.Notes,
			&rr.StorageDBID, &rr.StorageTable); err != nil {
			writeError(w, http.StatusInternalServerError, err.Error())
			return
		}
		runs = append(runs, rr)
	}
	writeJSON(w, http.StatusOK, map[string]any{"runs": runs, "count": len(runs)})
}

func (s *Server) handleDataFactoryDatabases(w http.ResponseWriter, r *http.Request) {
	db, err := s.dataFactoryDB()
	if err != nil {
		writeError(w, http.StatusServiceUnavailable, "data_factory.db unavailable: "+err.Error())
		return
	}

	ctx, cancel := context.WithTimeout(r.Context(), queryTimeout)
	defer cancel()

	rows, err := db.QueryContext(ctx, `
		SELECT id, kind, label, uri, description, tags_csv, last_seen_at,
		       table_count, size_bytes, created_at, updated_at
		FROM databases
		ORDER BY kind, label`)
	if err != nil {
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}
	defer rows.Close()

	out := make([]dataFactoryDatabase, 0, 16)
	for rows.Next() {
		var d dataFactoryDatabase
		if err := rows.Scan(&d.ID, &d.Kind, &d.Label, &d.URI, &d.Description,
			&d.TagsCSV, &d.LastSeenAt, &d.TableCount, &d.SizeBytes,
			&d.CreatedAt, &d.UpdatedAt); err != nil {
			writeError(w, http.StatusInternalServerError, err.Error())
			return
		}
		out = append(out, d)
	}
	writeJSON(w, http.StatusOK, map[string]any{"databases": out, "count": len(out)})
}

// dataFactoryTable is the JSON row for /api/datafactory/tables.
type dataFactoryTable struct {
	DatabaseID    string `json:"database_id"`
	DatabaseLabel string `json:"database_label"`
	DatabaseKind  string `json:"database_kind"`
	TableName     string `json:"table_name"`
	RowCount      int64  `json:"row_count"`
	Error         string `json:"error,omitempty"`
}

// tableNameRE restricts table names to alphanumeric + underscore + dot.
// This prevents SQL injection in the preview queries.
var tableNameRE = regexp.MustCompile(`^[A-Za-z0-9_.]+$`)

// previewColumn is a JSON column descriptor for the preview response.
type previewColumn struct {
	Name string `json:"name"`
	Type string `json:"type"`
}

// previewResponse is the JSON shape of /api/datafactory/preview.
type previewResponse struct {
	DatabaseID string          `json:"database_id"`
	TableName  string          `json:"table_name"`
	Columns    []previewColumn `json:"columns"`
	Rows       [][]string      `json:"rows"`
	TotalRows  int64           `json:"total_rows"`
	Limit      int             `json:"limit"`
	Offset     int             `json:"offset"`
}

// handleDataFactoryPreview serves:
//
//	GET /api/datafactory/preview?database_id=<id>&table=<name>&limit=N&offset=N
//
// Supports kind="sqlite" and kind="duckdb" databases registered in
// data_factory.databases. Returns up to 1000 rows (default 100).
func (s *Server) handleDataFactoryPreview(w http.ResponseWriter, r *http.Request) {
	q := r.URL.Query()

	databaseID := q.Get("database_id")
	tableName := q.Get("table")
	if databaseID == "" || tableName == "" {
		writeError(w, http.StatusBadRequest, "database_id and table are required")
		return
	}
	if !tableNameRE.MatchString(tableName) {
		writeError(w, http.StatusBadRequest,
			fmt.Sprintf("invalid table name %q: only [A-Za-z0-9_.] allowed", tableName))
		return
	}

	limit := 100
	if l := q.Get("limit"); l != "" {
		if n, err := strconv.Atoi(l); err == nil {
			switch {
			case n < 1:
				limit = 1
			case n > 1000:
				limit = 1000
			default:
				limit = n
			}
		}
	}
	offset := 0
	if o := q.Get("offset"); o != "" {
		if n, err := strconv.Atoi(o); err == nil && n >= 0 {
			offset = n
		}
	}

	// Look up the database in data_factory.db.
	dfDB, err := s.dataFactoryDB()
	if err != nil {
		writeError(w, http.StatusServiceUnavailable, "data_factory.db unavailable: "+err.Error())
		return
	}

	ctx, cancel := context.WithTimeout(r.Context(), 30*queryTimeout)
	defer cancel()

	var dbKind, dbURI string
	row := dfDB.QueryRowContext(ctx, `SELECT kind, uri FROM databases WHERE id = ?`, databaseID)
	if err := row.Scan(&dbKind, &dbURI); err != nil {
		if err == sql.ErrNoRows {
			writeError(w, http.StatusNotFound, fmt.Sprintf("database_id %q not found", databaseID))
		} else {
			writeError(w, http.StatusInternalServerError, err.Error())
		}
		return
	}

	// Resolve absolute path.
	root := os.Getenv("FN_REGISTRY_ROOT")
	if root == "" {
		root = "/home/lucas/fn_registry"
	}
	dbPath := dbURI
	if !filepath.IsAbs(dbPath) {
		dbPath = filepath.Join(root, dbURI)
	}

	var resp previewResponse
	resp.DatabaseID = databaseID
	resp.TableName = tableName
	resp.Limit = limit
	resp.Offset = offset

	switch dbKind {
	case "sqlite":
		if err := previewSQLite(dbPath, tableName, limit, offset, &resp); err != nil {
			writeError(w, http.StatusInternalServerError, "sqlite preview: "+err.Error())
			return
		}
	case "duckdb":
		if err := previewDuckDB(dbPath, tableName, limit, offset, &resp); err != nil {
			writeError(w, http.StatusInternalServerError, "duckdb preview: "+err.Error())
			return
		}
	default:
		writeError(w, http.StatusBadRequest, fmt.Sprintf("unsupported database kind: %q", dbKind))
		return
	}

	writeJSON(w, http.StatusOK, resp)
}

// previewSQLite fetches schema + rows from a SQLite database.
func previewSQLite(path, table string, limit, offset int, out *previewResponse) error {
	db, err := sql.Open("sqlite3", "file:"+path+"?mode=ro")
	if err != nil {
		return err
	}
	defer db.Close()

	// Schema via PRAGMA table_info.
	rows, err := db.Query(fmt.Sprintf(`PRAGMA table_info("%s")`, table))
	if err != nil {
		return fmt.Errorf("PRAGMA table_info: %w", err)
	}
	defer rows.Close()
	for rows.Next() {
		var cid int
		var name, typ, dflt string
		var notNull, pk int
		if err := rows.Scan(&cid, &name, &typ, &notNull, &dflt, &pk); err != nil {
			return err
		}
		out.Columns = append(out.Columns, previewColumn{Name: name, Type: typ})
	}
	_ = rows.Close()
	if len(out.Columns) == 0 {
		return fmt.Errorf("table %q not found or has no columns", table)
	}

	// Total row count.
	cntRow := db.QueryRow(fmt.Sprintf(`SELECT count(*) FROM "%s"`, table))
	_ = cntRow.Scan(&out.TotalRows)

	// Data rows.
	dataRows, err := db.Query(
		fmt.Sprintf(`SELECT * FROM "%s" LIMIT ? OFFSET ?`, table),
		limit, offset,
	)
	if err != nil {
		return fmt.Errorf("SELECT: %w", err)
	}
	defer dataRows.Close()

	nCols := len(out.Columns)
	for dataRows.Next() {
		vals := make([]interface{}, nCols)
		ptrs := make([]interface{}, nCols)
		for i := range vals {
			ptrs[i] = &vals[i]
		}
		if err := dataRows.Scan(ptrs...); err != nil {
			return err
		}
		row := make([]string, nCols)
		for i, v := range vals {
			switch t := v.(type) {
			case nil:
				row[i] = ""
			case []byte:
				row[i] = string(t)
			default:
				row[i] = fmt.Sprintf("%v", t)
			}
		}
		out.Rows = append(out.Rows, row)
	}
	if out.Rows == nil {
		out.Rows = [][]string{}
	}
	return nil
}

// duckPreviewResult is used to unmarshal the Python subprocess output.
type duckPreviewResult struct {
	Columns  []previewColumn `json:"columns"`
	Rows     [][]string      `json:"rows"`
	TotalRows int64          `json:"total_rows"`
}

// previewDuckDB fetches schema + rows from a DuckDB database via Python subprocess.
func previewDuckDB(path, table string, limit, offset int, out *previewResponse) error {
	pyBin := "/home/lucas/fn_registry/python/.venv/bin/python3"
	script := fmt.Sprintf(
		`import duckdb, json, sys
path, table, lim, off = %q, %q, %d, %d
c = duckdb.connect(path, read_only=True)
cols = c.execute(f"DESCRIBE \"{table}\"").fetchall()
cols_json = [{"name": r[0], "type": r[1]} for r in cols]
rows = c.execute(f"SELECT * FROM \"{table}\" LIMIT {lim} OFFSET {off}").fetchall()
rows_str = [[str(v) if v is not None else "" for v in r] for r in rows]
total = c.execute(f"SELECT count(*) FROM \"{table}\"").fetchone()[0]
print(json.dumps({"columns": cols_json, "rows": rows_str, "total_rows": total}))
`, path, table, limit, offset)

	cmd := exec.Command(pyBin, "-c", script)
	rawOut, err := cmd.Output()
	if err != nil {
		// Capture stderr for better error messages.
		if ee, ok := err.(*exec.ExitError); ok {
			return fmt.Errorf("python subprocess: %w: %s", err, string(ee.Stderr))
		}
		return fmt.Errorf("python subprocess: %w", err)
	}

	var result duckPreviewResult
	if err := json.Unmarshal(rawOut, &result); err != nil {
		return fmt.Errorf("parse subprocess output: %w", err)
	}
	out.Columns = result.Columns
	out.TotalRows = result.TotalRows
	out.Rows = result.Rows
	if out.Rows == nil {
		out.Rows = [][]string{}
	}
	return nil
}

func (s *Server) handleDataFactoryTables(w http.ResponseWriter, r *http.Request) {
	db, err := s.dataFactoryDB()
	if err != nil {
		writeError(w, http.StatusServiceUnavailable, "data_factory.db unavailable: "+err.Error())
		return
	}

	ctx, cancel := context.WithTimeout(r.Context(), queryTimeout)
	defer cancel()

	rows, err := db.QueryContext(ctx, `
		SELECT id, kind, label, uri FROM databases ORDER BY kind, label`)
	if err != nil {
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}
	defer rows.Close()

	// Resolve registry root for relative URIs.
	root := os.Getenv("FN_REGISTRY_ROOT")
	if root == "" {
		root = "/home/lucas/fn_registry"
	}

	out := make([]dataFactoryTable, 0, 16)
	for rows.Next() {
		var id, kind, label, uri string
		if err := rows.Scan(&id, &kind, &label, &uri); err != nil {
			continue
		}
		path := uri
		if !filepath.IsAbs(path) {
			path = filepath.Join(root, uri)
		}
		// Existence check.
		if _, errStat := os.Stat(path); errStat != nil {
			out = append(out, dataFactoryTable{
				DatabaseID: id, DatabaseLabel: label, DatabaseKind: kind,
				TableName: "(file not found)", Error: errStat.Error(),
			})
			continue
		}
		tables, errTables := listTablesForDatabase(kind, path)
		if errTables != nil {
			out = append(out, dataFactoryTable{
				DatabaseID: id, DatabaseLabel: label, DatabaseKind: kind,
				TableName: "(error)", Error: errTables.Error(),
			})
			continue
		}
		for _, t := range tables {
			out = append(out, dataFactoryTable{
				DatabaseID: id, DatabaseLabel: label, DatabaseKind: kind,
				TableName: t.Name, RowCount: t.RowCount,
			})
		}
	}
	writeJSON(w, http.StatusOK, map[string]any{"tables": out, "count": len(out)})
}