package fileproc

import (
	"bufio"
	"fmt"
	"io"
	"os"
	"path/filepath"
	"strings"

	"github.com/ivuorinen/gibidify/gibidiutils"
)

// YAMLWriter handles YAML format output with streaming support.
type YAMLWriter struct {
	outFile *os.File
}

// NewYAMLWriter creates a new YAML writer.
func NewYAMLWriter(outFile *os.File) *YAMLWriter {
	return &YAMLWriter{outFile: outFile}
}

const (
	maxPathLength     = 4096 // Maximum total path length
	maxFilenameLength = 255  // Maximum individual filename component length
)

// validatePathComponents validates individual path components for security issues.
func validatePathComponents(trimmed, cleaned string, components []string) error {
	for i, component := range components {
		// Reject path components that are exactly ".." (path traversal)
		if component == ".." {
			return gibidiutils.NewStructuredError(
				gibidiutils.ErrorTypeValidation,
				gibidiutils.CodeValidationPath,
				"path traversal not allowed",
				trimmed,
				map[string]any{
					"path":              trimmed,
					"cleaned":           cleaned,
					"invalid_component": component,
					"component_index":   i,
				},
			)
		}

		// Reject empty components (e.g., from "foo//bar")
		if component == "" && i > 0 && i < len(components)-1 {
			return gibidiutils.NewStructuredError(
				gibidiutils.ErrorTypeValidation,
				gibidiutils.CodeValidationPath,
				"path contains empty component",
				trimmed,
				map[string]any{
					"path":            trimmed,
					"cleaned":         cleaned,
					"component_index": i,
				},
			)
		}

		// Enforce maximum filename length for each component
		if len(component) > maxFilenameLength {
			return gibidiutils.NewStructuredError(
				gibidiutils.ErrorTypeValidation,
				gibidiutils.CodeValidationPath,
				"path component exceeds maximum length",
				trimmed,
				map[string]any{
					"component":        component,
					"component_length": len(component),
					"max_length":       maxFilenameLength,
					"component_index":  i,
				},
			)
		}
	}
	return nil
}

// validatePath validates and sanitizes a file path for safe output.
// It rejects absolute paths, path traversal attempts, empty paths, and overly long paths.
func validatePath(path string) error {
	// Reject empty paths
	trimmed := strings.TrimSpace(path)
	if trimmed == "" {
		return gibidiutils.NewStructuredError(
			gibidiutils.ErrorTypeValidation,
			gibidiutils.CodeValidationRequired,
			"file path cannot be empty",
			"",
			nil,
		)
	}

	// Enforce maximum path length to prevent resource abuse
	if len(trimmed) > maxPathLength {
		return gibidiutils.NewStructuredError(
			gibidiutils.ErrorTypeValidation,
			gibidiutils.CodeValidationPath,
			"path exceeds maximum length",
			trimmed,
			map[string]any{
				"path_length": len(trimmed),
				"max_length":  maxPathLength,
			},
		)
	}

	// Reject absolute paths
	if filepath.IsAbs(trimmed) {
		return gibidiutils.NewStructuredError(
			gibidiutils.ErrorTypeValidation,
			gibidiutils.CodeValidationPath,
			"absolute paths are not allowed",
			trimmed,
			map[string]any{"path": trimmed},
		)
	}

	// Validate original trimmed path components before cleaning
	origComponents := strings.Split(filepath.ToSlash(trimmed), "/")
	for _, comp := range origComponents {
		if comp == "" || comp == "." || comp == ".." {
			return gibidiutils.NewStructuredError(
				gibidiutils.ErrorTypeValidation,
				gibidiutils.CodeValidationPath,
				"invalid or traversal path component in original path",
				trimmed,
				map[string]any{"path": trimmed, "component": comp},
			)
		}
	}

	// Clean the path to normalize it
	cleaned := filepath.Clean(trimmed)

	// After cleaning, ensure it's still relative and doesn't start with /
	if filepath.IsAbs(cleaned) || strings.HasPrefix(cleaned, "/") {
		return gibidiutils.NewStructuredError(
			gibidiutils.ErrorTypeValidation,
			gibidiutils.CodeValidationPath,
			"path must be relative",
			trimmed,
			map[string]any{"path": trimmed, "cleaned": cleaned},
		)
	}

	// Split into components and validate each one
	// Use ToSlash to normalize for cross-platform validation
	components := strings.Split(filepath.ToSlash(cleaned), "/")
	return validatePathComponents(trimmed, cleaned, components)
}

// Start writes the YAML header.
func (w *YAMLWriter) Start(prefix, suffix string) error {
	// Write YAML header
	if _, err := fmt.Fprintf(
		w.outFile, "prefix: %s\nsuffix: %s\nfiles:\n",
		gibidiutils.EscapeForYAML(prefix), gibidiutils.EscapeForYAML(suffix),
	); err != nil {
		return gibidiutils.WrapError(
			err,
			gibidiutils.ErrorTypeIO,
			gibidiutils.CodeIOWrite,
			"failed to write YAML header",
		)
	}
	return nil
}

// WriteFile writes a file entry in YAML format.
func (w *YAMLWriter) WriteFile(req WriteRequest) error {
	if req.IsStream {
		return w.writeStreaming(req)
	}
	return w.writeInline(req)
}

// Close writes the YAML footer (no footer needed for YAML).
func (w *YAMLWriter) Close() error {
	return nil
}

// writeStreaming writes a large file as YAML in streaming chunks.
func (w *YAMLWriter) writeStreaming(req WriteRequest) error {
	// Validate path before using it
	if err := validatePath(req.Path); err != nil {
		return err
	}

	// Check for nil reader
	if req.Reader == nil {
		return gibidiutils.WrapError(
			nil, gibidiutils.ErrorTypeValidation, gibidiutils.CodeValidationRequired,
			"nil reader in write request",
		).WithFilePath(req.Path)
	}

	defer gibidiutils.SafeCloseReader(req.Reader, req.Path)

	language := detectLanguage(req.Path)

	// Write YAML file entry start
	if _, err := fmt.Fprintf(
		w.outFile, "  - path: %s\n    language: %s\n    content: |\n",
		gibidiutils.EscapeForYAML(req.Path), language,
	); err != nil {
		return gibidiutils.WrapError(
			err, gibidiutils.ErrorTypeIO, gibidiutils.CodeIOWrite,
			"failed to write YAML file start",
		).WithFilePath(req.Path)
	}

	// Stream content with YAML indentation
	return w.streamYAMLContent(req.Reader, req.Path)
}

// writeInline writes a small file directly as YAML.
func (w *YAMLWriter) writeInline(req WriteRequest) error {
	// Validate path before using it
	if err := validatePath(req.Path); err != nil {
		return err
	}

	language := detectLanguage(req.Path)
	fileData := FileData{
		Path:     req.Path,
		Content:  req.Content,
		Language: language,
	}

	// Write YAML entry
	if _, err := fmt.Fprintf(
		w.outFile, "  - path: %s\n    language: %s\n    content: |\n",
		gibidiutils.EscapeForYAML(fileData.Path), fileData.Language,
	); err != nil {
		return gibidiutils.WrapError(
			err, gibidiutils.ErrorTypeIO, gibidiutils.CodeIOWrite,
			"failed to write YAML entry start",
		).WithFilePath(req.Path)
	}

	// Write indented content
	lines := strings.Split(fileData.Content, "\n")
	for _, line := range lines {
		if _, err := fmt.Fprintf(w.outFile, "      %s\n", line); err != nil {
			return gibidiutils.WrapError(
				err, gibidiutils.ErrorTypeIO, gibidiutils.CodeIOWrite,
				"failed to write YAML content line",
			).WithFilePath(req.Path)
		}
	}

	return nil
}

// streamYAMLContent streams content with YAML indentation.
func (w *YAMLWriter) streamYAMLContent(reader io.Reader, path string) error {
	scanner := bufio.NewScanner(reader)
	// Increase buffer size to handle long lines (up to 10MB per line)
	buf := make([]byte, 0, 64*1024)
	scanner.Buffer(buf, 10*1024*1024)

	for scanner.Scan() {
		line := scanner.Text()
		if _, err := fmt.Fprintf(w.outFile, "      %s\n", line); err != nil {
			return gibidiutils.WrapError(
				err, gibidiutils.ErrorTypeIO, gibidiutils.CodeIOWrite,
				"failed to write YAML line",
			).WithFilePath(path)
		}
	}

	if err := scanner.Err(); err != nil {
		return gibidiutils.WrapError(
			err, gibidiutils.ErrorTypeIO, gibidiutils.CodeIOFileRead,
			"failed to scan YAML content",
		).WithFilePath(path)
	}
	return nil
}

// startYAMLWriter handles YAML format output with streaming support.
func startYAMLWriter(outFile *os.File, writeCh <-chan WriteRequest, done chan<- struct{}, prefix, suffix string) {
	defer close(done)

	writer := NewYAMLWriter(outFile)

	// Start writing
	if err := writer.Start(prefix, suffix); err != nil {
		gibidiutils.LogError("Failed to write YAML header", err)
		return
	}

	// Process files
	for req := range writeCh {
		if err := writer.WriteFile(req); err != nil {
			gibidiutils.LogError("Failed to write YAML file", err)
		}
	}

	// Close writer
	if err := writer.Close(); err != nil {
		gibidiutils.LogError("Failed to write YAML end", err)
	}
}