package main

import (
	"context"
	"database/sql"
	"encoding/csv"
	"fmt"
	"io"
	"log"
	"os"
	"os/signal"
	"path/filepath"
	"regexp"
	"strings"

	_ "github.com/mattn/go-sqlite3"

	"golang.org/x/term"
)

var MaxRecords = 1_000_000_000

func main() {
	if len(os.Args) != 2 {
		log.Printf("usage: %s <csv_path>", os.Args[0])
		os.Exit(1)
	}
	csvPath, err := filepath.Abs(os.Args[1])
	if err != nil {
		log.Fatal(fmt.Sprintf("resolve absolute path for '%s': %v", os.Args[1], err))
	}
	ctx, cancel := context.WithCancel(context.Background())

	go func() {
		_, stop := signal.NotifyContext(
			ctx,
			os.Interrupt,
			os.Kill,
		)
		sig := make(chan os.Signal, 1)
		<-sig
		stop()
		log.Print("caught signal; shutting down")
		cancel()
	}()

	// open csv for read
	f, err := os.Open(os.Args[1])
	if err != nil {
		log.Fatal(fmt.Sprintf("open csv: %v", err))
	}
	defer func() {
		if err := f.Close(); err != nil {
			log.Printf("close csv '%s': %v", csvPath, err)
		}
	}()
	r := csv.NewReader(f)
	r.ReuseRecord = true

	// open db
	tmp := strings.TrimSuffix(csvPath, ".csv")
	dbPath := tmp + ".db"
	name := scrubName(filepath.Base(tmp))
	// no need to rollback or be crash resistant
	params := "?_synchronous=0&_journal_mode=OFF&_temp_store=2"
	db, err := sql.Open("sqlite3", dbPath+params)
	if err != nil {
		log.Fatal(fmt.Sprintf("open db '%s': %v", dbPath, err))
	}
	defer func() {
		if err := db.Close(); err != nil {
			log.Printf("close db '%s': %v", dbPath, err)
		}
	}()

	// create table, prepare insert
	var insert *sql.Stmt
	headers := make([]string, 0, 32)

	rec, err := r.Read()
	if err != nil && err != io.EOF {
		log.Fatal(fmt.Sprintf("read csv '%s': %v", csvPath, err))
	}
	for _, f := range rec {
		f = scrubName(f)
		headers = append(headers, f)
	}
	_, err = createTable(ctx, db, name, headers)
	if err != nil {
		log.Fatal(fmt.Sprintf("create table '%s': %v", name, err))
	}
	insert, err = genInsert(ctx, db, name, headers)
	if err != nil {
		log.Fatal(fmt.Sprintf("prepare insert: %v", err))
	}
	defer func() {
		if err := insert.Close(); err != nil {
			log.Printf("close prepared insert: %v", err)
		}
	}()

	// insert records
	tx, err := db.BeginTx(ctx, nil)
	if err != nil {
		log.Fatal(fmt.Sprintf("begin transaction: %v", err))
	}
	i := 0
	for {
		i++
		if i >= MaxRecords {
			panic(fmt.Sprintf("BUG: max record limit reached: %d", MaxRecords))
		}
		if ctx.Err() != nil {
			break
		}
		// Print count for every thousand-ish records
		if i&4095 == 0 {
			printStatus(i)
		}
		if i&65535 == 0 {
			if err := tx.Commit(); err != nil {
				log.Fatal(fmt.Printf("commit transaction: %v", err))
			}
			tx, err = db.BeginTx(ctx, nil)
			if err != nil {
				log.Fatal(fmt.Sprintf("begin transaction: %v", err))
			}
		}

		rec, err := r.Read()
		if err != nil {
			fmt.Println()

			if err == io.EOF {
				log.Printf("read %d records", i)
			} else {
				log.Printf("read csv '%s': %v", csvPath, err)
			}
			break
		}
		// Rather slow, doing this for every record, but since
		// we cannot know how many fields will exist ahead of
		// time (we compile *now*, not after we've read the
		// headers), we cannot simply enter, say, 27 arguments,
		// each converted to `any`, by hand. It may be faster to
		// simply print the SQL statements and pipe them to
		// sqlite. Should check this.
		args := make([]any, len(rec))
		for j := 0; j < len(rec); j++ {
			args[j] = any(rec[j])
		}
		_, err = insert.ExecContext(ctx, args...)
		if err != nil {
			log.Fatal(fmt.Sprintf("insert record '%#v': %v", rec, err))
		}
	}
	if err := tx.Commit(); err != nil {
		log.Fatal(fmt.Sprintf("commit transaction: %v", err))
	}
}

func printStatus(n int) {
	if term.IsTerminal(int(os.Stdout.Fd())) {
		fmt.Printf("\x1b[%dG", 1)
		fmt.Printf("%d", n)
	}
}

func genInsert(
	ctx context.Context,
	db *sql.DB,
	name string,
	headers []string,
) (*sql.Stmt, error) {
	var b strings.Builder

	b.WriteString(fmt.Sprintf("INSERT INTO %s (", name))
	for i, h := range headers {
		if i != 0 {
			b.WriteString(", ")
		}
		b.WriteString(h)
	}
	b.WriteString(") VALUES (")
	for i := 0; i < len(headers); i++ {
		if i != 0 {
			b.WriteString(", ")
		}
		b.WriteString(fmt.Sprintf("$%d", i+1))
	}
	b.WriteString(");")
	log.Printf("debug: prepare insert: %s\n", b.String())

	return db.PrepareContext(ctx, b.String())
}

func createTable(
	ctx context.Context,
	db *sql.DB,
	name string,
	headers []string,
) (sql.Result, error) {
	var b strings.Builder

	b.WriteString(
		fmt.Sprintf("CREATE TABLE IF NOT EXISTS %s (", name),
	)

	for i, h := range headers {
		if i != 0 {
			b.WriteString(", ")
		}
		b.WriteString(fmt.Sprintf("%s text", h))
	}
	b.WriteString(");")

	return db.ExecContext(ctx, b.String())
}

var badRunes = regexp.MustCompile(`[^a-zA-Z0-9_\-\.]+`)
var badFirst = regexp.MustCompile(`^[^a-zA-Z]+`)
var parens = regexp.MustCompile(`\([^\)]*\)`)
var spaces = regexp.MustCompile(`\s+`)
var hyphens = regexp.MustCompile(`\-+`)
var unders = regexp.MustCompile(`_+`)

func scrubName(s string) string {
	s = strings.ToLower(s)
	s = badFirst.ReplaceAllLiteralString(s, "")
	s = parens.ReplaceAllLiteralString(s, "")
	s = strings.TrimSpace(s)
	s = spaces.ReplaceAllLiteralString(s, "_")
	s = badRunes.ReplaceAllLiteralString(s, "_")
	s = hyphens.ReplaceAllLiteralString(s, "_")
	s = unders.ReplaceAllLiteralString(s, "_")
	s = strings.TrimSuffix(s, "_")

	return s
}