// Copyright 2025 The Gitea Authors. All rights reserved.
// SPDX-License-Identifier: MIT

package sourcegraph

import (
	"bytes"
	"context"
	"crypto/tls"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"time"

	"code.gitea.io/gitea/modules/cache"
	"code.gitea.io/gitea/modules/log"
	"code.gitea.io/gitea/modules/setting"
)

// Client wraps Sourcegraph GraphQL API
type Client struct {
	baseURL     string
	accessToken string
	httpClient  *http.Client
}

// Range represents a range in source code
type Range struct {
	Start Position `json:"start"`
	End   Position `json:"end"`
}

// Position represents a position in source code
type Position struct {
	Line      int `json:"line"`
	Character int `json:"character"`
}

// HoverResult represents hover documentation response
type HoverResult struct {
	Contents string `json:"contents"` // Markdown content
	Range    *Range `json:"range,omitempty"`
}

// Location represents a code location
type Location struct {
	Repo      string `json:"repo"`
	Path      string `json:"path"`
	Line      int    `json:"line"`
	Character int    `json:"character"`
	URL       string `json:"url,omitempty"`
}

var defaultClient *Client

// GetClient returns the singleton Sourcegraph client
func GetClient() *Client {
	return defaultClient
}

// NewClient creates a new Sourcegraph client with current settings
func NewClient() *Client {
	transport := &http.Transport{
		TLSClientConfig: &tls.Config{
			InsecureSkipVerify: setting.Sourcegraph.SkipTLSVerify, //nolint:gosec
		},
	}

	return &Client{
		baseURL:     setting.Sourcegraph.URL,
		accessToken: setting.Sourcegraph.AccessToken,
		httpClient: &http.Client{
			Timeout:   time.Duration(setting.Sourcegraph.Timeout) * time.Second,
			Transport: transport,
		},
	}
}

// graphqlRequest performs a GraphQL request to Sourcegraph
func (c *Client) graphqlRequest(ctx context.Context, query string, variables map[string]any) (json.RawMessage, error) {
	body := map[string]any{
		"query":     query,
		"variables": variables,
	}
	bodyBytes, err := json.Marshal(body)
	if err != nil {
		return nil, fmt.Errorf("failed to marshal request: %w", err)
	}

	log.Debug("Sourcegraph GraphQL request to %s: variables=%v", c.baseURL+"/.api/graphql", variables)

	req, err := http.NewRequestWithContext(ctx, http.MethodPost, c.baseURL+"/.api/graphql", bytes.NewReader(bodyBytes))
	if err != nil {
		return nil, fmt.Errorf("failed to create request: %w", err)
	}

	req.Header.Set("Content-Type", "application/json")
	if c.accessToken != "" {
		req.Header.Set("Authorization", "token "+c.accessToken)
	}

	resp, err := c.httpClient.Do(req)
	if err != nil {
		return nil, fmt.Errorf("request failed: %w", err)
	}
	defer resp.Body.Close()

	respBody, err := io.ReadAll(resp.Body)
	if err != nil {
		return nil, fmt.Errorf("failed to read response: %w", err)
	}

	if resp.StatusCode != http.StatusOK {
		log.Warn("Sourcegraph GraphQL error status %d: %s", resp.StatusCode, string(respBody))
		return nil, fmt.Errorf("unexpected status %d: %s", resp.StatusCode, string(respBody))
	}

	log.Debug("Sourcegraph GraphQL response: %s", string(respBody))

	var result struct {
		Data   json.RawMessage `json:"data"`
		Errors []struct {
			Message string `json:"message"`
		} `json:"errors"`
	}
	if err := json.Unmarshal(respBody, &result); err != nil {
		return nil, fmt.Errorf("failed to unmarshal response: %w", err)
	}

	if len(result.Errors) > 0 {
		log.Warn("Sourcegraph GraphQL errors: %v", result.Errors)
		return nil, fmt.Errorf("graphql error: %s", result.Errors[0].Message)
	}

	return result.Data, nil
}

// cacheKey generates a cache key for code intelligence queries
func cacheKey(queryType, repo, rev, path string, line, char int) string {
	return fmt.Sprintf("sg:%s:%s:%s:%s:%d:%d", queryType, repo, rev, path, line, char)
}

// Hover queries documentation at a position
func (c *Client) Hover(ctx context.Context, repo, rev, path string, line, char int) (*HoverResult, error) {
	key := cacheKey("hover", repo, rev, path, line, char)

	log.Debug("Sourcegraph Hover request: repo=%s rev=%s path=%s line=%d char=%d", repo, rev, path, line, char)

	// Try cache first
	if cached, hit := cache.GetCache().Get(key); hit {
		var result HoverResult
		if err := json.Unmarshal([]byte(cached), &result); err == nil {
			log.Debug("Sourcegraph Hover cache hit")
			return &result, nil
		}
	}

	data, err := c.graphqlRequest(ctx, hoverQuery, map[string]any{
		"repo": repo,
		"rev":  rev,
		"path": path,
		"line": line,
		"char": char,
	})
	if err != nil {
		return nil, err
	}

	result, err := parseHoverResponse(data)
	if err != nil {
		return nil, err
	}

	// Cache the result
	if result != nil {
		if resultBytes, err := json.Marshal(result); err == nil {
			_ = cache.GetCache().Put(key, string(resultBytes), int64(setting.Sourcegraph.CacheTTL))
		}
	}

	return result, nil
}

// Definition queries for symbol definition
func (c *Client) Definition(ctx context.Context, repo, rev, path string, line, char int) ([]Location, error) {
	key := cacheKey("def", repo, rev, path, line, char)

	// Try cache first
	if cached, hit := cache.GetCache().Get(key); hit {
		var result []Location
		if err := json.Unmarshal([]byte(cached), &result); err == nil {
			return result, nil
		}
	}

	data, err := c.graphqlRequest(ctx, definitionQuery, map[string]any{
		"repo": repo,
		"rev":  rev,
		"path": path,
		"line": line,
		"char": char,
	})
	if err != nil {
		return nil, err
	}

	result, err := parseLocationsResponse(data, "definitions")
	if err != nil {
		return nil, err
	}

	// Cache the result
	if resultBytes, err := json.Marshal(result); err == nil {
		_ = cache.GetCache().Put(key, string(resultBytes), int64(setting.Sourcegraph.CacheTTL))
	}

	return result, nil
}

// References queries for all references to a symbol
func (c *Client) References(ctx context.Context, repo, rev, path string, line, char int) ([]Location, error) {
	key := cacheKey("refs", repo, rev, path, line, char)

	// Try cache first
	if cached, hit := cache.GetCache().Get(key); hit {
		var result []Location
		if err := json.Unmarshal([]byte(cached), &result); err == nil {
			return result, nil
		}
	}

	data, err := c.graphqlRequest(ctx, referencesQuery, map[string]any{
		"repo": repo,
		"rev":  rev,
		"path": path,
		"line": line,
		"char": char,
	})
	if err != nil {
		return nil, err
	}

	result, err := parseLocationsResponse(data, "references")
	if err != nil {
		return nil, err
	}

	// Cache the result
	if resultBytes, err := json.Marshal(result); err == nil {
		_ = cache.GetCache().Put(key, string(resultBytes), int64(setting.Sourcegraph.CacheTTL))
	}

	return result, nil
}

// SyncRepository notifies Sourcegraph to re-sync a repository
func (c *Client) SyncRepository(ctx context.Context, repoName string) error {
	// Use the repository sync mutation
	_, err := c.graphqlRequest(ctx, syncRepoMutation, map[string]any{
		"repo": repoName,
	})
	if err != nil {
		log.Warn("Sourcegraph sync failed for %s: %v", repoName, err)
		return err
	}
	log.Debug("Sourcegraph sync triggered for %s", repoName)
	return nil
}