package sync

import (
	"bufio"
	"database/sql"
	"fmt"
	"os"
	"os/exec"
	"path/filepath"
	"slices"
	"strconv"

	"git.meatbag.se/vlv/shell-history/internal/model"
)

func Run(d *sql.DB, args []string) error {
	if len(args) < 1 {
		fmt.Fprintln(os.Stderr, "usage: shist sync DIR")
		os.Exit(1)
	}
	gitDir := args[0]

	if err := export(d, gitDir); err != nil {
		return fmt.Errorf("export: %w", err)
	}

	if err := gitSync(gitDir); err != nil {
		return fmt.Errorf("git sync: %w", err)
	}

	if err := importAll(d, gitDir); err != nil {
		return fmt.Errorf("import: %w", err)
	}

	fmt.Println("Sync complete.")
	return nil
}

func export(d *sql.DB, gitDir string) error {
	var lastID int64
	err := d.QueryRow(`SELECT COALESCE(value, '0') FROM sync_meta WHERE key = 'last_export_id'`).Scan(&lastID)
	if err == sql.ErrNoRows {
		lastID = 0
	} else if err != nil {
		return err
	}

	rows, err := d.Query(
		`SELECT id, timestamp, hostname, working_dir, command FROM history WHERE id > ? ORDER BY id`,
		lastID,
	)
	if err != nil {
		return err
	}
	defer rows.Close()

	// Group entries by date for file output
	files := make(map[string][]string) // date -> lines
	var maxID int64
	var count int

	for rows.Next() {
		var id int64
		var e model.Entry
		if err := rows.Scan(&id, &e.Timestamp, &e.Hostname, &e.WorkingDir, &e.Command); err != nil {
			return err
		}
		// Extract date from timestamp (first 10 chars of ISO 8601)
		date := e.Timestamp[:10]
		files[date] = append(files[date], e.Format())
		if id > maxID {
			maxID = id
		}
		count++
	}
	if err := rows.Err(); err != nil {
		return err
	}

	if count == 0 {
		fmt.Println("No new entries to export.")
		return nil
	}

	// Write/append to log files, then sort each
	for date, lines := range files {
		path := filepath.Join(gitDir, "zsh-history-"+date+".log")

		// Read existing lines
		existing, _ := readLines(path)
		all := append(existing, lines...)
		slices.Sort(all)
		all = slices.Compact(all)

		if err := writeLines(path, all); err != nil {
			return fmt.Errorf("write %s: %w", path, err)
		}
	}

	// Update last_export_id
	_, err = d.Exec(
		`INSERT OR REPLACE INTO sync_meta (key, value) VALUES ('last_export_id', ?)`,
		strconv.FormatInt(maxID, 10),
	)
	if err != nil {
		return err
	}

	fmt.Printf("Exported %d entries.\n", count)
	return nil
}

func gitSync(gitDir string) error {
	git := func(args ...string) error {
		cmd := exec.Command("git", args...)
		cmd.Dir = gitDir
		cmd.Stdout = os.Stdout
		cmd.Stderr = os.Stderr
		return cmd.Run()
	}

	// Stage log files
	matches, _ := filepath.Glob(filepath.Join(gitDir, "zsh-history-*.log"))
	if len(matches) > 0 {
		addArgs := []string{"add"}
		for _, m := range matches {
			addArgs = append(addArgs, filepath.Base(m))
		}
		// Also add .gitattributes if present
		if _, err := os.Stat(filepath.Join(gitDir, ".gitattributes")); err == nil {
			addArgs = append(addArgs, ".gitattributes")
		}
		git(addArgs...)
	}

	// Commit if there are staged changes
	cmd := exec.Command("git", "diff", "--cached", "--quiet")
	cmd.Dir = gitDir
	if err := cmd.Run(); err != nil {
		// There are staged changes
		hostname, _ := os.Hostname()
		git("commit", "-m", hostname+": update history")
	}

	// Pull
	if err := git("pull", "--no-edit", "--no-rebase"); err != nil {
		return fmt.Errorf("git pull: %w", err)
	}

	// Re-sort log files after merge
	needsCommit := false
	logFiles, _ := filepath.Glob(filepath.Join(gitDir, "zsh-history-*.log"))
	for _, f := range logFiles {
		if sortFile(f) {
			needsCommit = true
		}
	}

	if needsCommit {
		addArgs := []string{"add"}
		for _, f := range logFiles {
			addArgs = append(addArgs, filepath.Base(f))
		}
		git(addArgs...)
		hostname, _ := os.Hostname()
		git("commit", "-m", hostname+": sort after merge")
	}

	// Push
	return git("push")
}

func importAll(d *sql.DB, gitDir string) error {
	files, err := filepath.Glob(filepath.Join(gitDir, "zsh-history-*.log"))
	if err != nil {
		return err
	}

	var totalInserted int

	for _, f := range files {
		inserted, err := importFile(d, f)
		if err != nil {
			return fmt.Errorf("import %s: %w", f, err)
		}
		totalInserted += inserted
	}

	// Update last_export_id to current max
	var maxID int64
	d.QueryRow("SELECT COALESCE(MAX(id), 0) FROM history").Scan(&maxID)
	d.Exec(
		`INSERT OR REPLACE INTO sync_meta (key, value) VALUES ('last_export_id', ?)`,
		strconv.FormatInt(maxID, 10),
	)

	if totalInserted > 0 {
		fmt.Printf("Imported %d new entries from git.\n", totalInserted)
	}
	return nil
}

func importFile(d *sql.DB, path string) (int, error) {
	f, err := os.Open(path)
	if err != nil {
		return 0, err
	}
	defer f.Close()

	tx, err := d.Begin()
	if err != nil {
		return 0, err
	}
	defer tx.Rollback()

	stmt, err := tx.Prepare(
		`INSERT OR IGNORE INTO history (timestamp, hostname, working_dir, command) VALUES (?, ?, ?, ?)`,
	)
	if err != nil {
		return 0, err
	}
	defer stmt.Close()

	scanner := bufio.NewScanner(f)
	scanner.Buffer(make([]byte, 0, 1024*1024), 1024*1024)

	var inserted, batch int
	for scanner.Scan() {
		entry, err := model.ParseLine(scanner.Text())
		if err != nil {
			continue
		}
		res, err := stmt.Exec(entry.Timestamp, entry.Hostname, entry.WorkingDir, entry.Command)
		if err != nil {
			return inserted, err
		}
		n, _ := res.RowsAffected()
		inserted += int(n)

		batch++
		if batch >= 1000 {
			if err := tx.Commit(); err != nil {
				return inserted, err
			}
			tx, err = d.Begin()
			if err != nil {
				return inserted, err
			}
			stmt, err = tx.Prepare(
				`INSERT OR IGNORE INTO history (timestamp, hostname, working_dir, command) VALUES (?, ?, ?, ?)`,
			)
			if err != nil {
				return inserted, err
			}
			batch = 0
		}
	}

	if err := scanner.Err(); err != nil {
		return inserted, err
	}

	return inserted, tx.Commit()
}

func readLines(path string) ([]string, error) {
	f, err := os.Open(path)
	if err != nil {
		return nil, err
	}
	defer f.Close()

	var lines []string
	scanner := bufio.NewScanner(f)
	scanner.Buffer(make([]byte, 0, 1024*1024), 1024*1024)
	for scanner.Scan() {
		if line := scanner.Text(); line != "" {
			lines = append(lines, line)
		}
	}
	return lines, scanner.Err()
}

func writeLines(path string, lines []string) error {
	f, err := os.Create(path)
	if err != nil {
		return err
	}
	defer f.Close()

	w := bufio.NewWriter(f)
	for _, line := range lines {
		w.WriteString(line)
		w.WriteByte('\n')
	}
	return w.Flush()
}

func sortFile(path string) bool {
	lines, err := readLines(path)
	if err != nil || len(lines) == 0 {
		return false
	}

	if slices.IsSorted(lines) {
		return false
	}

	slices.Sort(lines)
	lines = slices.Compact(lines)

	writeLines(path, lines)
	return true
}