package api

import (
	"encoding/csv"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"sort"
	"strconv"
	"strings"
	"time"

	"github.com/kindredsystems/silo/internal/db"
	"github.com/kindredsystems/silo/internal/partnum"
)

// CSV Export/Import handlers for bulk data management

// CSVExportOptions controls what fields to include in export.
type CSVExportOptions struct {
	IncludeProperties bool
	IncludeRevisions  bool
}

// CSVImportResult represents the result of an import operation.
type CSVImportResult struct {
	TotalRows    int            `json:"total_rows"`
	SuccessCount int            `json:"success_count"`
	ErrorCount   int            `json:"error_count"`
	Errors       []CSVImportErr `json:"errors,omitempty"`
	CreatedItems []string       `json:"created_items,omitempty"`
}

// CSVImportErr represents an error on a specific row.
type CSVImportErr struct {
	Row     int    `json:"row"`
	Field   string `json:"field,omitempty"`
	Message string `json:"message"`
}

// Standard CSV columns for export/import
var csvColumns = []string{
	"part_number",
	"item_type",
	"description",
	"current_revision",
	"created_at",
	"updated_at",
	"project",
	"category",
}

// HandleExportCSV exports items to CSV format.
func (s *Server) HandleExportCSV(w http.ResponseWriter, r *http.Request) {
	ctx := r.Context()

	// Parse query options
	opts := db.ListOptions{
		ItemType: r.URL.Query().Get("type"),
		Search:   r.URL.Query().Get("search"),
		Project:  r.URL.Query().Get("project"),
		Limit:    10000, // Max export limit
	}

	includeProps := r.URL.Query().Get("include_properties") == "true"

	// Fetch items
	items, err := s.items.List(ctx, opts)
	if err != nil {
		s.logger.Error().Err(err).Msg("failed to list items for export")
		writeError(w, http.StatusInternalServerError, "export_failed", err.Error())
		return
	}

	// Collect all property keys if including properties
	propKeys := make(map[string]bool)
	itemProps := make(map[string]map[string]any) // part_number -> properties

	if includeProps {
		for _, item := range items {
			revisions, err := s.items.GetRevisions(ctx, item.ID)
			if err != nil {
				continue
			}
			for _, rev := range revisions {
				if rev.RevisionNumber == item.CurrentRevision && rev.Properties != nil {
					itemProps[item.PartNumber] = rev.Properties
					for k := range rev.Properties {
						propKeys[k] = true
					}
					break
				}
			}
		}
	}

	// Build header row
	headers := make([]string, len(csvColumns))
	copy(headers, csvColumns)

	// Add property columns (sorted for consistency)
	sortedPropKeys := make([]string, 0, len(propKeys))
	for k := range propKeys {
		// Skip internal/system properties
		if !strings.HasPrefix(k, "_") {
			sortedPropKeys = append(sortedPropKeys, k)
		}
	}
	sort.Strings(sortedPropKeys)
	headers = append(headers, sortedPropKeys...)

	// Set response headers for CSV download
	filename := fmt.Sprintf("silo-export-%s.csv", time.Now().Format("2006-01-02"))
	w.Header().Set("Content-Type", "text/csv")
	w.Header().Set("Content-Disposition", fmt.Sprintf("attachment; filename=\"%s\"", filename))

	// Write CSV
	writer := csv.NewWriter(w)
	defer writer.Flush()

	// Write header
	if err := writer.Write(headers); err != nil {
		s.logger.Error().Err(err).Msg("failed to write CSV header")
		return
	}

	// Write data rows
	for _, item := range items {
		row := make([]string, len(headers))

		// Parse part number to extract project and category
		project, category := parsePartNumber(item.PartNumber)

		// Standard columns
		row[0] = item.PartNumber
		row[1] = item.ItemType
		row[2] = item.Description
		row[3] = strconv.Itoa(item.CurrentRevision)
		row[4] = item.CreatedAt.Format(time.RFC3339)
		row[5] = item.UpdatedAt.Format(time.RFC3339)
		row[6] = project
		row[7] = category

		// Property columns
		if includeProps {
			props := itemProps[item.PartNumber]
			for i, key := range sortedPropKeys {
				colIdx := len(csvColumns) + i
				if props != nil {
					if val, ok := props[key]; ok {
						row[colIdx] = formatPropertyValue(val)
					}
				}
			}
		}

		if err := writer.Write(row); err != nil {
			s.logger.Error().Err(err).Str("part_number", item.PartNumber).Msg("failed to write CSV row")
			continue
		}
	}

	s.logger.Info().Int("count", len(items)).Msg("exported items to CSV")
}

// HandleImportCSV imports items from a CSV file.
func (s *Server) HandleImportCSV(w http.ResponseWriter, r *http.Request) {
	ctx := r.Context()

	// Parse multipart form (max 10MB)
	if err := r.ParseMultipartForm(10 << 20); err != nil {
		writeError(w, http.StatusBadRequest, "invalid_form", err.Error())
		return
	}

	// Get file
	file, _, err := r.FormFile("file")
	if err != nil {
		writeError(w, http.StatusBadRequest, "missing_file", "CSV file is required")
		return
	}
	defer file.Close()

	// Get options
	dryRun := r.FormValue("dry_run") == "true"
	schemaName := r.FormValue("schema")
	if schemaName == "" {
		schemaName = "kindred-rd"
	}

	// Parse CSV
	reader := csv.NewReader(file)
	reader.TrimLeadingSpace = true

	// Read header
	headers, err := reader.Read()
	if err != nil {
		writeError(w, http.StatusBadRequest, "invalid_csv", "Failed to read CSV header")
		return
	}

	// Build column index map
	colIndex := make(map[string]int)
	for i, h := range headers {
		colIndex[strings.ToLower(strings.TrimSpace(h))] = i
	}

	// Validate required columns
	requiredCols := []string{"project", "category"}
	for _, col := range requiredCols {
		if _, ok := colIndex[col]; !ok {
			writeError(w, http.StatusBadRequest, "missing_column", fmt.Sprintf("Required column '%s' not found", col))
			return
		}
	}

	result := CSVImportResult{
		Errors:       make([]CSVImportErr, 0),
		CreatedItems: make([]string, 0),
	}

	// Process rows
	rowNum := 1 // Start at 1 (header is row 0)
	for {
		record, err := reader.Read()
		if err == io.EOF {
			break
		}
		if err != nil {
			result.Errors = append(result.Errors, CSVImportErr{
				Row:     rowNum,
				Message: fmt.Sprintf("Failed to parse row: %v", err),
			})
			result.ErrorCount++
			rowNum++
			continue
		}

		result.TotalRows++
		rowNum++

		// Extract values
		project := getCSVValue(record, colIndex, "project")
		category := getCSVValue(record, colIndex, "category")
		description := getCSVValue(record, colIndex, "description")
		partNumber := getCSVValue(record, colIndex, "part_number")

		// Validate project
		if project == "" {
			result.Errors = append(result.Errors, CSVImportErr{
				Row:     rowNum,
				Field:   "project",
				Message: "Project code is required",
			})
			result.ErrorCount++
			continue
		}

		// Validate category
		if category == "" {
			result.Errors = append(result.Errors, CSVImportErr{
				Row:     rowNum,
				Field:   "category",
				Message: "Category code is required",
			})
			result.ErrorCount++
			continue
		}

		// Build properties from extra columns
		properties := make(map[string]any)
		properties["project"] = strings.ToUpper(project)
		properties["category"] = strings.ToUpper(category)

		for col, idx := range colIndex {
			// Skip standard columns
			if isStandardColumn(col) {
				continue
			}
			if idx < len(record) && record[idx] != "" {
				properties[col] = parsePropertyValue(record[idx])
			}
		}

		// If part_number is provided, check if it exists
		if partNumber != "" {
			existing, _ := s.items.GetByPartNumber(ctx, partNumber)
			if existing != nil {
				result.Errors = append(result.Errors, CSVImportErr{
					Row:     rowNum,
					Field:   "part_number",
					Message: fmt.Sprintf("Part number '%s' already exists", partNumber),
				})
				result.ErrorCount++
				continue
			}
		}

		if dryRun {
			// In dry-run mode, just validate
			result.SuccessCount++
			continue
		}

		// Generate part number if not provided
		if partNumber == "" {
			input := partnum.Input{
				SchemaName: schemaName,
				Values: map[string]string{
					"project":  strings.ToUpper(project),
					"category": strings.ToUpper(category),
				},
			}

			partNumber, err = s.partgen.Generate(ctx, input)
			if err != nil {
				result.Errors = append(result.Errors, CSVImportErr{
					Row:     rowNum,
					Message: fmt.Sprintf("Failed to generate part number: %v", err),
				})
				result.ErrorCount++
				continue
			}
		}

		// Determine item type from category
		itemType := "part"
		if len(category) > 0 {
			switch category[0] {
			case 'A':
				itemType = "assembly"
			case 'T':
				itemType = "tooling"
			}
		}

		// Create item
		item := &db.Item{
			PartNumber:  partNumber,
			ItemType:    itemType,
			Description: description,
		}

		if err := s.items.Create(ctx, item, properties); err != nil {
			result.Errors = append(result.Errors, CSVImportErr{
				Row:     rowNum,
				Message: fmt.Sprintf("Failed to create item: %v", err),
			})
			result.ErrorCount++
			continue
		}

		result.SuccessCount++
		result.CreatedItems = append(result.CreatedItems, partNumber)
	}

	s.logger.Info().
		Int("total", result.TotalRows).
		Int("success", result.SuccessCount).
		Int("errors", result.ErrorCount).
		Bool("dry_run", dryRun).
		Msg("CSV import completed")

	writeJSON(w, http.StatusOK, result)
}

// HandleCSVTemplate returns an empty CSV template with headers.
func (s *Server) HandleCSVTemplate(w http.ResponseWriter, r *http.Request) {
	schemaName := r.URL.Query().Get("schema")
	if schemaName == "" {
		schemaName = "kindred-rd"
	}

	sch, ok := s.schemas[schemaName]
	if !ok {
		writeError(w, http.StatusNotFound, "not_found", "Schema not found")
		return
	}

	// Build headers: standard columns + default property columns from schema
	headers := []string{
		"project",
		"category",
		"description",
	}

	// Add default property columns from schema
	if sch.PropertySchemas != nil && sch.PropertySchemas.Defaults != nil {
		propNames := make([]string, 0, len(sch.PropertySchemas.Defaults))
		for name := range sch.PropertySchemas.Defaults {
			propNames = append(propNames, name)
		}
		sort.Strings(propNames)
		headers = append(headers, propNames...)
	}

	// Set response headers
	filename := fmt.Sprintf("silo-import-template-%s.csv", schemaName)
	w.Header().Set("Content-Type", "text/csv")
	w.Header().Set("Content-Disposition", fmt.Sprintf("attachment; filename=\"%s\"", filename))

	writer := csv.NewWriter(w)
	defer writer.Flush()

	// Write header row
	if err := writer.Write(headers); err != nil {
		s.logger.Error().Err(err).Msg("failed to write CSV template header")
		return
	}

	// Write example row
	exampleRow := make([]string, len(headers))
	exampleRow[0] = "PROJ1" // project
	exampleRow[1] = "F01"   // category
	exampleRow[2] = "Example Item Description"
	// Leave property columns empty

	if err := writer.Write(exampleRow); err != nil {
		s.logger.Error().Err(err).Msg("failed to write CSV template example")
		return
	}
}

// Helper functions

func parsePartNumber(pn string) (project, category string) {
	parts := strings.Split(pn, "-")
	if len(parts) >= 2 {
		project = parts[0]
		category = parts[1]
	}
	return
}

func formatPropertyValue(v any) string {
	switch val := v.(type) {
	case string:
		return val
	case float64:
		if val == float64(int64(val)) {
			return strconv.FormatInt(int64(val), 10)
		}
		return strconv.FormatFloat(val, 'f', -1, 64)
	case int:
		return strconv.Itoa(val)
	case int64:
		return strconv.FormatInt(val, 10)
	case bool:
		return strconv.FormatBool(val)
	case nil:
		return ""
	default:
		// For complex types, use JSON
		b, _ := json.Marshal(val)
		return string(b)
	}
}

func parsePropertyValue(s string) any {
	s = strings.TrimSpace(s)
	if s == "" {
		return nil
	}

	// Try boolean
	if s == "true" {
		return true
	}
	if s == "false" {
		return false
	}

	// Try integer
	if i, err := strconv.ParseInt(s, 10, 64); err == nil {
		return i
	}

	// Try float
	if f, err := strconv.ParseFloat(s, 64); err == nil {
		return f
	}

	// Try JSON (for arrays/objects)
	if (strings.HasPrefix(s, "[") && strings.HasSuffix(s, "]")) ||
		(strings.HasPrefix(s, "{") && strings.HasSuffix(s, "}")) {
		var v any
		if err := json.Unmarshal([]byte(s), &v); err == nil {
			return v
		}
	}

	// Default to string
	return s
}

func getCSVValue(record []string, colIndex map[string]int, column string) string {
	if idx, ok := colIndex[column]; ok && idx < len(record) {
		return strings.TrimSpace(record[idx])
	}
	return ""
}

func isStandardColumn(col string) bool {
	standardCols := map[string]bool{
		"part_number":      true,
		"item_type":        true,
		"description":      true,
		"current_revision": true,
		"created_at":       true,
		"updated_at":       true,
		"project":          true,
		"category":         true,
	}
	return standardCols[col]
}