// Package index provides index-level operations for OpenSearch.
package index

import (
	"bytes"
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"os"

	"es-demo/client"

	"github.com/opensearch-project/opensearch-go/v2/opensearchapi"
)

var (
	// ErrIndexNotFound is returned when the specified index does not exist.
	ErrIndexNotFound = errors.New("index not found")

	// ErrIndexAlreadyExists is returned when trying to create an index that already exists.
	ErrIndexAlreadyExists = errors.New("index already exists")

	// ErrInvalidIndexName is returned when the index name is invalid.
	ErrInvalidIndexName = errors.New("invalid index name")
)

// IndexSettings represents the settings for an index.
type IndexSettings struct {
	NumberOfShards   int `json:"number_of_shards,omitempty"`
	NumberOfReplicas int `json:"number_of_replicas,omitempty"`
}

// IndexConfig represents the complete configuration for creating an index.
type IndexConfig struct {
	Settings *IndexSettings `json:"settings,omitempty"`
	Mappings map[string]any `json:"mappings,omitempty"`
	Aliases  map[string]any `json:"aliases,omitempty"`
}

// IndexInfo represents information about an index.
type IndexInfo struct {
	Name     string
	Settings *IndexSettings
	Mappings map[string]any
	Aliases  map[string]any
}

// CreateIndex creates a new index with the specified configuration.
func CreateIndex(ctx context.Context, c *client.Client, name string, config *IndexConfig) error {
	if name == "" {
		return ErrInvalidIndexName
	}

	// Build request body
	var body io.Reader
	if config != nil {
		data, err := json.Marshal(config)
		if err != nil {
			return fmt.Errorf("failed to marshal index config: %w", err)
		}
		body = bytes.NewReader(data)
	}

	req := opensearchapi.IndicesCreateRequest{
		Index: name,
		Body:  body,
	}

	res, err := req.Do(ctx, c.GetClient())
	if err != nil {
		return fmt.Errorf("failed to execute create index request: %w", err)
	}
	defer func() {
		if closeErr := res.Body.Close(); closeErr != nil {
			fmt.Fprintf(os.Stderr, "warning: failed to close response body: %v\n", closeErr)
		}
	}()

	if res.IsError() {
		bodyBytes, _ := io.ReadAll(res.Body)
		if res.StatusCode == 400 {
			return fmt.Errorf("%w: %s", ErrIndexAlreadyExists, string(bodyBytes))
		}
		return fmt.Errorf("create index failed with status %s: %s", res.Status(), string(bodyBytes))
	}

	return nil
}

// GetIndex retrieves information about an index.
func GetIndex(ctx context.Context, c *client.Client, name string) (*IndexInfo, error) {
	if name == "" {
		return nil, ErrInvalidIndexName
	}

	req := opensearchapi.IndicesGetRequest{
		Index: []string{name},
	}

	res, err := req.Do(ctx, c.GetClient())
	if err != nil {
		return nil, fmt.Errorf("failed to execute get index request: %w", err)
	}
	defer func() {
		if closeErr := res.Body.Close(); closeErr != nil {
			fmt.Fprintf(os.Stderr, "warning: failed to close response body: %v\n", closeErr)
		}
	}()

	if res.StatusCode == 404 {
		return nil, ErrIndexNotFound
	}

	if res.IsError() {
		bodyBytes, _ := io.ReadAll(res.Body)
		return nil, fmt.Errorf("get index failed with status %s: %s", res.Status(), string(bodyBytes))
	}

	// Parse response
	var response map[string]struct {
		Settings struct {
			Index struct {
				NumberOfShards   string `json:"number_of_shards"`
				NumberOfReplicas string `json:"number_of_replicas"`
			} `json:"index"`
		} `json:"settings"`
		Mappings map[string]any `json:"mappings"`
		Aliases  map[string]any `json:"aliases"`
	}

	if err := json.NewDecoder(res.Body).Decode(&response); err != nil {
		return nil, fmt.Errorf("failed to decode index info: %w", err)
	}

	indexData, exists := response[name]
	if !exists {
		return nil, ErrIndexNotFound
	}

	info := &IndexInfo{
		Name:     name,
		Mappings: indexData.Mappings,
		Aliases:  indexData.Aliases,
	}

	return info, nil
}

// DeleteIndex deletes an index.
func DeleteIndex(ctx context.Context, c *client.Client, name string) error {
	if name == "" {
		return ErrInvalidIndexName
	}

	req := opensearchapi.IndicesDeleteRequest{
		Index: []string{name},
	}

	res, err := req.Do(ctx, c.GetClient())
	if err != nil {
		return fmt.Errorf("failed to execute delete index request: %w", err)
	}
	defer func() {
		if closeErr := res.Body.Close(); closeErr != nil {
			fmt.Fprintf(os.Stderr, "warning: failed to close response body: %v\n", closeErr)
		}
	}()

	if res.StatusCode == 404 {
		return ErrIndexNotFound
	}

	if res.IsError() {
		bodyBytes, _ := io.ReadAll(res.Body)
		return fmt.Errorf("delete index failed with status %s: %s", res.Status(), string(bodyBytes))
	}

	return nil
}

// IndexExists checks if an index exists.
func IndexExists(ctx context.Context, c *client.Client, name string) (bool, error) {
	if name == "" {
		return false, ErrInvalidIndexName
	}

	req := opensearchapi.IndicesExistsRequest{
		Index: []string{name},
	}

	res, err := req.Do(ctx, c.GetClient())
	if err != nil {
		return false, fmt.Errorf("failed to execute exists request: %w", err)
	}
	defer func() {
		if closeErr := res.Body.Close(); closeErr != nil {
			fmt.Fprintf(os.Stderr, "warning: failed to close response body: %v\n", closeErr)
		}
	}()

	return res.StatusCode == 200, nil
}

// ListIndices lists all indices matching a pattern (use "*" for all).
func ListIndices(ctx context.Context, c *client.Client, pattern string) ([]string, error) {
	if pattern == "" {
		pattern = "*"
	}

	req := opensearchapi.CatIndicesRequest{
		Index:  []string{pattern},
		Format: "json",
	}

	res, err := req.Do(ctx, c.GetClient())
	if err != nil {
		return nil, fmt.Errorf("failed to execute list indices request: %w", err)
	}
	defer func() {
		if closeErr := res.Body.Close(); closeErr != nil {
			fmt.Fprintf(os.Stderr, "warning: failed to close response body: %v\n", closeErr)
		}
	}()

	if res.IsError() {
		bodyBytes, _ := io.ReadAll(res.Body)
		return nil, fmt.Errorf("list indices failed with status %s: %s", res.Status(), string(bodyBytes))
	}

	var indices []struct {
		Index string `json:"index"`
	}

	if err := json.NewDecoder(res.Body).Decode(&indices); err != nil {
		return nil, fmt.Errorf("failed to decode indices list: %w", err)
	}

	result := make([]string, len(indices))
	for i, idx := range indices {
		result[i] = idx.Index
	}

	return result, nil
}