package workflow

import (
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"io"
	"maps"
	"net/http"
	neturl "net/url"
	"strings"
	"sync"
	"time"
)

// ServiceAdapter defines the interface for calling project services
type ServiceAdapter interface {
	// Call invokes a service with the given parameters and returns the result
	Call(ctx context.Context, serviceName string, params map[string]any) (*ServiceResult, error)
}

// ComponentAdapter defines the interface for calling system components
type ComponentAdapter interface {
	// Call invokes a component with the given parameters and returns the result
	Call(ctx context.Context, componentID string, params map[string]any) (map[string]any, error)
}

// LLMAdapter defines the interface for calling LLM services
type LLMAdapter interface {
	// Call invokes an LLM with the given parameters
	// For streaming responses, the stream channel will receive chunks
	Call(ctx context.Context, params map[string]any, stream chan<- string) (map[string]any, error)
}

// FileAdapter defines the interface for file operations
type FileAdapter interface {
	// Read reads a file from the input path
	Read(ctx context.Context, path string) ([]byte, error)

	// Write writes content to an artifact path with the specified mode
	Write(ctx context.Context, path string, content []byte, mode WriteMode) error

	// Exists checks if a file exists
	Exists(ctx context.Context, path string) (bool, error)

	// List lists files matching a pattern
	List(ctx context.Context, pattern string) ([]string, error)
}

// APIAdapter defines the interface for calling third-party HTTP APIs
type APIAdapter interface {
	// Call invokes an HTTP API with the given definition and parameters
	// Returns the parsed response body (typically JSON)
	Call(ctx context.Context, apiDef *APIDefinition, params map[string]any) (map[string]any, error)
}

// DocAdapter defines the interface for resolving semantic document references
type DocAdapter interface {
	// Get retrieves the content of a document by its ID
	Get(ctx context.Context, docID string) (string, error)
}

// LLMAdapterRegistry holds multiple named LLM adapters and resolves the
// correct adapter for a given model spec string (v3.16+).
//
// Model spec formats:
//   - "" (empty): use default adapter with its configured model
//   - "openai" (no /): use the "openai" adapter with its configured default model
//   - "openai/gpt-4.1" (has /): use the "openai" adapter with model override "gpt-4.1"
type LLMAdapterRegistry struct {
	adapters        map[string]LLMAdapter // keyed by provider name
	defaultAdapter  LLMAdapter
	defaultProvider string
}

// NewLLMAdapterRegistry creates a new multi-provider adapter registry.
func NewLLMAdapterRegistry(defaultAdapter LLMAdapter, defaultProvider string) *LLMAdapterRegistry {
	return &LLMAdapterRegistry{
		adapters:        make(map[string]LLMAdapter),
		defaultAdapter:  defaultAdapter,
		defaultProvider: defaultProvider,
	}
}

// Register adds a provider adapter to the registry.
func (r *LLMAdapterRegistry) Register(provider string, adapter LLMAdapter) {
	r.adapters[provider] = adapter
}

// Resolve returns the adapter and optional model override for the given model spec.
// If modelSpec is empty, returns the default adapter with no override.
// If modelSpec has no "/", it is treated as a pure provider name (adapter's default model is used).
// If modelSpec has "/", it is split into provider + modelId.
func (r *LLMAdapterRegistry) Resolve(modelSpec string) (adapter LLMAdapter, modelOverride string, err error) {
	if modelSpec == "" {
		return r.defaultAdapter, "", nil
	}
	if strings.Contains(modelSpec, "/") {
		parts := strings.SplitN(modelSpec, "/", 2)
		provider, modelId := parts[0], parts[1]
		a, ok := r.adapters[provider]
		if !ok {
			return nil, "", fmt.Errorf("unsupported LLM provider: %q", provider)
		}
		return a, modelId, nil
	}
	// Provider-only: use that adapter's configured default model
	a, ok := r.adapters[modelSpec]
	if !ok {
		return nil, "", fmt.Errorf("unsupported LLM provider: %q", modelSpec)
	}
	return a, "", nil
}

// Call implements LLMAdapter by delegating to the default adapter.
// This makes LLMAdapterRegistry usable as a drop-in LLMAdapter for backward compatibility.
func (r *LLMAdapterRegistry) Call(ctx context.Context, params map[string]any, stream chan<- string) (map[string]any, error) {
	return r.defaultAdapter.Call(ctx, params, stream)
}

// DefaultDocAdapter is a simple in-memory doc adapter for testing
type DefaultDocAdapter struct {
	docs map[string]string
	mu   sync.RWMutex
}

// NewDefaultDocAdapter creates a new default doc adapter
func NewDefaultDocAdapter() *DefaultDocAdapter {
	return &DefaultDocAdapter{
		docs: make(map[string]string),
	}
}

// SetDoc stores a document by ID
func (d *DefaultDocAdapter) SetDoc(id, content string) {
	d.mu.Lock()
	defer d.mu.Unlock()
	d.docs[id] = content
}

// Get implements DocAdapter
func (d *DefaultDocAdapter) Get(ctx context.Context, docID string) (string, error) {
	d.mu.RLock()
	defer d.mu.RUnlock()
	content, ok := d.docs[docID]
	if !ok {
		return "", fmt.Errorf("document not found: %s", docID)
	}
	return content, nil
}

// DefaultServiceAdapter is a simple in-memory service adapter for testing
type DefaultServiceAdapter struct {
	handlers map[string]ServiceHandler
	mu       sync.RWMutex
}

// ServiceHandler is a function that handles service calls
type ServiceHandler func(ctx context.Context, params map[string]any) (*ServiceResult, error)

// NewDefaultServiceAdapter creates a new default service adapter
func NewDefaultServiceAdapter() *DefaultServiceAdapter {
	return &DefaultServiceAdapter{
		handlers: make(map[string]ServiceHandler),
	}
}

// RegisterHandler registers a service handler
func (a *DefaultServiceAdapter) RegisterHandler(serviceName string, handler ServiceHandler) {
	a.mu.Lock()
	defer a.mu.Unlock()
	a.handlers[serviceName] = handler
}

// Call implements ServiceAdapter
func (a *DefaultServiceAdapter) Call(ctx context.Context, serviceName string, params map[string]any) (*ServiceResult, error) {
	a.mu.RLock()
	handler, ok := a.handlers[serviceName]
	a.mu.RUnlock()

	if !ok {
		// Return empty result if no handler
		return &ServiceResult{
			Data: make(map[string]any),
		}, nil
	}
	return handler(ctx, params)
}

// DefaultComponentAdapter is a simple in-memory component adapter for testing
type DefaultComponentAdapter struct {
	handlers map[string]ComponentHandler
	mu       sync.RWMutex
}

// ComponentHandler is a function that handles component calls
type ComponentHandler func(ctx context.Context, params map[string]any) (map[string]any, error)

// NewDefaultComponentAdapter creates a new default component adapter
func NewDefaultComponentAdapter() *DefaultComponentAdapter {
	return &DefaultComponentAdapter{
		handlers: make(map[string]ComponentHandler),
	}
}

// RegisterHandler registers a component handler
func (a *DefaultComponentAdapter) RegisterHandler(componentID string, handler ComponentHandler) {
	a.mu.Lock()
	defer a.mu.Unlock()
	a.handlers[componentID] = handler
}

// Call implements ComponentAdapter
func (a *DefaultComponentAdapter) Call(ctx context.Context, componentID string, params map[string]any) (map[string]any, error) {
	a.mu.RLock()
	handler, ok := a.handlers[componentID]
	a.mu.RUnlock()

	if !ok {
		return make(map[string]any), nil
	}
	return handler(ctx, params)
}

// DefaultLLMAdapter is a simple in-memory LLM adapter for testing
type DefaultLLMAdapter struct {
	handler LLMHandler
	mu      sync.RWMutex
}

// LLMHandler is a function that handles LLM calls
type LLMHandler func(ctx context.Context, params map[string]any, stream chan<- string) (map[string]any, error)

// NewDefaultLLMAdapter creates a new default LLM adapter
func NewDefaultLLMAdapter() *DefaultLLMAdapter {
	return &DefaultLLMAdapter{}
}

// SetHandler sets the LLM handler
func (a *DefaultLLMAdapter) SetHandler(handler LLMHandler) {
	a.mu.Lock()
	defer a.mu.Unlock()
	a.handler = handler
}

// Call implements LLMAdapter
func (a *DefaultLLMAdapter) Call(ctx context.Context, params map[string]any, stream chan<- string) (map[string]any, error) {
	a.mu.RLock()
	handler := a.handler
	a.mu.RUnlock()

	if handler == nil {
		return map[string]any{
			"content": "Mock LLM response",
		}, nil
	}
	return handler(ctx, params, stream)
}

// DefaultFileAdapter is a simple in-memory file adapter for testing
type DefaultFileAdapter struct {
	files map[string][]byte
	mu    sync.RWMutex
}

// NewDefaultFileAdapter creates a new default file adapter
func NewDefaultFileAdapter() *DefaultFileAdapter {
	return &DefaultFileAdapter{
		files: make(map[string][]byte),
	}
}

// Read implements FileAdapter
func (a *DefaultFileAdapter) Read(ctx context.Context, path string) ([]byte, error) {
	a.mu.RLock()
	content, ok := a.files[path]
	a.mu.RUnlock()

	if !ok {
		return nil, &FileNotFoundError{Path: path}
	}
	return content, nil
}

// Write implements FileAdapter
func (a *DefaultFileAdapter) Write(ctx context.Context, path string, content []byte, mode WriteMode) error {
	a.mu.Lock()
	defer a.mu.Unlock()

	switch mode {
	case WriteModeFailIfExists:
		if _, exists := a.files[path]; exists {
			return &FileExistsError{Path: path}
		}
		a.files[path] = content
	case WriteModeAppend:
		existing := a.files[path]
		a.files[path] = append(existing, content...)
	case WriteModePrepend:
		existing := a.files[path]
		a.files[path] = append(content, existing...)
	case WriteModeOverwrite:
		fallthrough
	default:
		a.files[path] = content
	}
	return nil
}

// Exists implements FileAdapter
func (a *DefaultFileAdapter) Exists(ctx context.Context, path string) (bool, error) {
	a.mu.RLock()
	_, exists := a.files[path]
	a.mu.RUnlock()

	return exists, nil
}

// List implements FileAdapter
func (a *DefaultFileAdapter) List(ctx context.Context, pattern string) ([]string, error) {
	a.mu.RLock()
	defer a.mu.RUnlock()

	var matches []string
	for path := range a.files {
		if matchPattern(path, pattern) {
			matches = append(matches, path)
		}
	}
	return matches, nil
}

// SetFile sets a file in the in-memory store (for testing)
func (a *DefaultFileAdapter) SetFile(path string, content []byte) {
	a.mu.Lock()
	defer a.mu.Unlock()
	a.files[path] = content
}

// GetFile gets a file from the in-memory store (for testing)
func (a *DefaultFileAdapter) GetFile(path string) []byte {
	a.mu.RLock()
	defer a.mu.RUnlock()
	return a.files[path]
}

// Errors

// FileNotFoundError is returned when a file is not found
type FileNotFoundError struct {
	Path string
}

func (e *FileNotFoundError) Error() string {
	return "file not found: " + e.Path
}

// FileExistsError is returned when a file already exists
type FileExistsError struct {
	Path string
}

func (e *FileExistsError) Error() string {
	return "file already exists: " + e.Path
}

// StreamWriter wraps an io.Writer for streaming output
type StreamWriter struct {
	writer io.Writer
}

// NewStreamWriter creates a new stream writer
func NewStreamWriter(w io.Writer) *StreamWriter {
	return &StreamWriter{writer: w}
}

// Write writes a chunk to the stream
func (sw *StreamWriter) Write(chunk string) error {
	_, err := sw.writer.Write([]byte(chunk))
	return err
}

// DefaultAPIAdapter is an HTTP client-based API adapter.
// Params accepted by Call (all optional):
//   - pathParams (object): values substituted into {placeholder} segments of the URL
//   - query      (object): appended as URL query string
//   - body       (any):    JSON-encoded request body; sets Content-Type: application/json
//   - headers    (object): per-request headers that override apiDef.Headers
//   - authToken  (string): resolved by the executor from apiDef.Auth; sent as Bearer token
//
// Result keys returned on success:
//   - _status (number): HTTP status code
//   - All top-level keys from the JSON response body, or "body" (string) for non-JSON responses
type DefaultAPIAdapter struct {
	client *http.Client
}

// NewDefaultAPIAdapter creates an adapter with a 30-second request timeout.
func NewDefaultAPIAdapter() *DefaultAPIAdapter {
	return &DefaultAPIAdapter{
		client: &http.Client{
			Timeout: 30 * time.Second,
		},
	}
}

// NewDefaultAPIAdapterWithTimeout creates an adapter with a custom timeout.
func NewDefaultAPIAdapterWithTimeout(timeout time.Duration) *DefaultAPIAdapter {
	return &DefaultAPIAdapter{
		client: &http.Client{Timeout: timeout},
	}
}

// Call implements APIAdapter.
func (a *DefaultAPIAdapter) Call(ctx context.Context, apiDef *APIDefinition, params map[string]any) (map[string]any, error) {
	// 1. Substitute {placeholder} path segments — values are URL-path-encoded.
	rawURL := apiDef.URL
	if pathParams, ok := params["pathParams"].(map[string]any); ok {
		for key, val := range pathParams {
			rawURL = strings.ReplaceAll(rawURL, "{"+key+"}", neturl.PathEscape(fmt.Sprintf("%v", val)))
		}
	}

	// 2. Append query string.
	if queryParams, ok := params["query"].(map[string]any); ok {
		q := neturl.Values{}
		for key, val := range queryParams {
			q.Set(key, fmt.Sprintf("%v", val))
		}
		if len(q) > 0 {
			rawURL += "?" + q.Encode()
		}
	}

	// 3. Marshal request body.
	var bodyReader io.Reader
	var hasBody bool
	if body, ok := params["body"]; ok && body != nil {
		bodyBytes, err := json.Marshal(body)
		if err != nil {
			return nil, fmt.Errorf("failed to marshal request body: %w", err)
		}
		bodyReader = bytes.NewReader(bodyBytes)
		hasBody = true
	}

	// 4. Build request bound to the workflow context so cancellation propagates.
	req, err := http.NewRequestWithContext(ctx, strings.ToUpper(apiDef.Method), rawURL, bodyReader)
	if err != nil {
		return nil, fmt.Errorf("failed to create HTTP request: %w", err)
	}

	// 5. Apply static headers from the API definition first.
	for key, val := range apiDef.Headers {
		req.Header.Set(key, val)
	}

	// 6. Per-call headers override static ones.
	if headers, ok := params["headers"].(map[string]any); ok {
		for key, val := range headers {
			req.Header.Set(key, fmt.Sprintf("%v", val))
		}
	}

	// 7. Set Content-Type when a body is present (unless caller already set it).
	if hasBody && req.Header.Get("Content-Type") == "" {
		req.Header.Set("Content-Type", "application/json")
	}

	// 8. Authorization header — token resolved by the executor from apiDef.Auth.
	if authToken, ok := params["authToken"].(string); ok && authToken != "" {
		req.Header.Set("Authorization", "Bearer "+authToken)
	}

	// 9. Execute request.
	resp, err := a.client.Do(req)
	if err != nil {
		return nil, fmt.Errorf("HTTP request failed: %w", err)
	}
	defer resp.Body.Close()

	// 10. Read full response body.
	respBody, err := io.ReadAll(resp.Body)
	if err != nil {
		return nil, fmt.Errorf("failed to read response body: %w", err)
	}

	// 11. Non-2xx → error with status and body for caller inspection.
	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
		return nil, fmt.Errorf("API returned status %d: %s", resp.StatusCode, string(respBody))
	}

	// 12. Build result: start with _status so callers can read it from _result._status.
	result := map[string]any{
		"_status": resp.StatusCode,
	}

	if len(respBody) == 0 {
		return result, nil
	}

	// 13. Merge JSON fields into result; fall back to raw "body" string for non-JSON.
	var parsed map[string]any
	if err := json.Unmarshal(respBody, &parsed); err != nil {
		result["body"] = string(respBody)
	} else {
		maps.Copy(result, parsed)
	}

	return result, nil
}