package command

import (
	"bufio"
	"fmt"
	"os"

	"git.gophernest.net/azpect/TextEditor/internal/action"
	"git.gophernest.net/azpect/TextEditor/internal/core"
	tea "github.com/charmbracelet/bubbletea"
)

func writeBuffer(m action.Model, buf *core.Buffer, args []string, force bool) (tea.Cmd, error) {
	// Key Steps:
	// - Backup Creation (if backup is set): Copy original to .bak file
	// - Line Ending Application: Apply fileformat setting (unix=\n, dos=\r\n, mac=\r)
	// - Character Encoding: Convert from internal representation to fileencoding
	// - Atomic Write: Write to temporary file first (.swp or similar)
	// - Atomic Rename: Rename temp file to target filename (atomic operation)
	// - Metadata Update: Clear modified flag, update timestamp
	// Safety Mechanisms:
	// " Vim's write safety
	// 1. Check file permissions
	// 2. If file exists and 'writebackup' set:
	//    - Create backup (.bak)
	// 3. Write to temporary file (.swp~)
	// 4. Verify write succeeded
	// 5. Rename temp to target (atomic)
	// 6. Remove backup if 'backup' not set
	// 7. Update buffer metadata

	// TODO: Implement atomic and safe writes

	// Check readonly flag ONLY if not forced with !
	if !force && buf.ReadOnly {
		return nil, fmt.Errorf("cannot write to 'readonly' buffer")
	}

	if !force && buf.Type == core.ScatchBuffer {
		return nil, fmt.Errorf("cannot write to buffer of type 'ScratchBuffer'")
	}

	// Get the filename; differs by the type
	var filename string
	if len(args) > 0 {
		filename = args[0]
	} else {
		if buf.Filename == "" {
			return nil, fmt.Errorf("cannot write: no file name provided")
		}
		filename = buf.Filename
	}

	file, err := os.OpenFile(filename, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0664)
	if err != nil {
		return nil, err
	}
	defer file.Close()

	// Same write operation regardless of where the file came from
	var bytes int

	// Using a bufio.Writer because its more efficient
	writer := bufio.NewWriter(file)
	for _, line := range buf.Lines {
		n, err := writer.WriteString(line.String() + "\n")
		if err != nil {
			return nil, err
		}

		bytes += n
	}

	if err := writer.Flush(); err != nil {
		return nil, err
	}

	m.SetCommandOutput(&core.CommandOutput{
		Lines:  []string{fmt.Sprintf("'%s', %dL %db written", filename, buf.LineCount(), bytes)},
		Inline: true,
	})
	buf.SetModified(false)

	return nil, nil
}