// Summary: Minimal LSP server over stdio; manages documents, dispatches requests, and tracks stats.
package lsp

import (
	"bufio"
	"encoding/json"
	"io"
	"log"
	"os"
	"strings"
	"sync"
	"time"

	"codeberg.org/snonux/hexai/internal/appconfig"
	"codeberg.org/snonux/hexai/internal/ignore"
	"codeberg.org/snonux/hexai/internal/llm"
	"codeberg.org/snonux/hexai/internal/logging"
	"codeberg.org/snonux/hexai/internal/runtimeconfig"
)

// Server implements a minimal LSP over stdio.
type Server struct {
	in          *bufio.Reader
	out         io.Writer
	outMu       sync.Mutex
	logger      *log.Logger
	exited      bool
	mu          sync.RWMutex
	docs        map[string]*document
	logContext  bool
	configStore *runtimeconfig.Store
	cfg         appconfig.App
	llmClient   llm.Client
	llmProvider string
	altClients  map[string]llm.Client
	lastInput   time.Time
	// LLM request stats
	llmReqTotal       int64
	llmSentBytesTotal int64
	llmRespTotal      int64
	llmRespBytesTotal int64
	startTime         time.Time
	// Small LRU cache for recent code completion outputs (keyed by context)
	compCache          map[string]string
	compCacheOrder     []string // most-recent at end; cap ~10
	pendingCompletions map[string][]CompletionItem
	configLoadOpts     appconfig.LoadOptions
	// Outgoing JSON-RPC id counter for server-initiated requests
	nextID      int64
	lastLLMCall time.Time

	completionsDisabled bool

	// Gitignore-aware file checker (nil when disabled)
	ignoreChecker *ignore.Checker

	// Dispatch table for JSON-RPC methods → handler functions
	handlers map[string]func(Request)
}

// ServerOptions collects configuration for NewServer to avoid long parameter lists.
type ServerOptions struct {
	LogContext        bool
	ConfigStore       *runtimeconfig.Store
	Config            *appconfig.App
	MaxTokens         int
	ContextMode       string
	WindowLines       int
	MaxContextTokens  int
	ConfigLoadOptions appconfig.LoadOptions

	Client                llm.Client
	TriggerCharacters     []string
	CodingTemperature     *float64
	ManualInvokeMinPrefix int
	CompletionDebounceMs  int
	CompletionThrottleMs  int
	CompletionWaitAll     *bool

	// Inline/chat triggers
	InlineOpen   string
	InlineClose  string
	ChatSuffix   string
	ChatPrefixes []string

	// Prompt templates
	PromptCompSysGeneral    string
	PromptCompSysParams     string
	PromptCompSysInline     string
	PromptCompUserGeneral   string
	PromptCompUserParams    string
	PromptCompExtraHeader   string
	PromptNativeCompletion  string
	PromptChatSystem        string
	PromptRewriteSystem     string
	PromptDiagnosticsSystem string
	PromptDocumentSystem    string
	PromptRewriteUser       string
	PromptDiagnosticsUser   string
	PromptDocumentUser      string
	PromptGoTestSystem      string
	PromptGoTestUser        string
	PromptSimplifySystem    string
	PromptSimplifyUser      string

	// Custom actions
	CustomActions []CustomAction

	// Gitignore-aware file checker (optional)
	IgnoreChecker *ignore.Checker
}

// CustomAction mirrors user-defined code actions passed from config.
type CustomAction struct {
	ID          string
	Title       string
	Kind        string
	Scope       string // "selection" | "diagnostics"
	Instruction string // if set, use rewrite templates
	System      string // optional when User is set
	User        string // if set, use this user template
}

func NewServer(r io.Reader, w io.Writer, logger *log.Logger, opts ServerOptions) *Server {
	s := &Server{in: bufio.NewReader(r), out: w, logger: logger, docs: make(map[string]*document), logContext: opts.LogContext, configStore: opts.ConfigStore}
	s.startTime = time.Now()
	s.compCache = make(map[string]string)
	s.pendingCompletions = make(map[string][]CompletionItem)
	s.applyOptions(opts)
	// Initialize dispatch table
	s.handlers = map[string]func(Request){
		"initialize":               s.handleInitialize,
		"initialized":              func(_ Request) { s.handleInitialized() },
		"shutdown":                 s.handleShutdown,
		"exit":                     func(_ Request) { s.handleExit() },
		"textDocument/didOpen":     s.handleDidOpen,
		"textDocument/didChange":   s.handleDidChange,
		"textDocument/didClose":    s.handleDidClose,
		"textDocument/completion":  s.handleCompletion,
		"textDocument/codeAction":  s.handleCodeAction,
		"codeAction/resolve":       s.handleCodeActionResolve,
		"workspace/executeCommand": s.handleExecuteCommand,
	}
	return s
}

func (s *Server) applyOptions(opts ServerOptions) {
	s.mu.Lock()
	defer s.mu.Unlock()
	s.logContext = opts.LogContext
	s.configLoadOpts = opts.ConfigLoadOptions
	if opts.ConfigStore != nil {
		s.configStore = opts.ConfigStore
	}
	if opts.Config != nil {
		s.cfg = *opts.Config
	} else if opts.ConfigStore != nil {
		s.cfg = opts.ConfigStore.Snapshot()
	} else {
		s.cfg = appconfig.App{}
		// populate from legacy ServerOptions fields
		s.cfg.MaxTokens = opts.MaxTokens
		s.cfg.ContextMode = opts.ContextMode
		s.cfg.ContextWindowLines = opts.WindowLines
		s.cfg.MaxContextTokens = opts.MaxContextTokens
		s.cfg.TriggerCharacters = append([]string{}, opts.TriggerCharacters...)
		s.cfg.CodingTemperature = opts.CodingTemperature
		s.cfg.ManualInvokeMinPrefix = opts.ManualInvokeMinPrefix
		s.cfg.CompletionDebounceMs = opts.CompletionDebounceMs
		s.cfg.CompletionThrottleMs = opts.CompletionThrottleMs
		s.cfg.CompletionWaitAll = opts.CompletionWaitAll
		s.cfg.InlineOpen = opts.InlineOpen
		s.cfg.InlineClose = opts.InlineClose
		s.cfg.ChatSuffix = opts.ChatSuffix
		s.cfg.ChatPrefixes = append([]string{}, opts.ChatPrefixes...)
		s.cfg.PromptCompletionSystemGeneral = opts.PromptCompSysGeneral
		s.cfg.PromptCompletionSystemParams = opts.PromptCompSysParams
		s.cfg.PromptCompletionSystemInline = opts.PromptCompSysInline
		s.cfg.PromptCompletionUserGeneral = opts.PromptCompUserGeneral
		s.cfg.PromptCompletionUserParams = opts.PromptCompUserParams
		s.cfg.PromptCompletionExtraHeader = opts.PromptCompExtraHeader
		s.cfg.PromptNativeCompletion = opts.PromptNativeCompletion
		s.cfg.PromptChatSystem = opts.PromptChatSystem
		s.cfg.PromptCodeActionRewriteSystem = opts.PromptRewriteSystem
		s.cfg.PromptCodeActionDiagnosticsSystem = opts.PromptDiagnosticsSystem
		s.cfg.PromptCodeActionDocumentSystem = opts.PromptDocumentSystem
		s.cfg.PromptCodeActionRewriteUser = opts.PromptRewriteUser
		s.cfg.PromptCodeActionDiagnosticsUser = opts.PromptDiagnosticsUser
		s.cfg.PromptCodeActionDocumentUser = opts.PromptDocumentUser
		s.cfg.PromptCodeActionGoTestSystem = opts.PromptGoTestSystem
		s.cfg.PromptCodeActionGoTestUser = opts.PromptGoTestUser
		s.cfg.PromptCodeActionSimplifySystem = opts.PromptSimplifySystem
		s.cfg.PromptCodeActionSimplifyUser = opts.PromptSimplifyUser
		s.cfg.CustomActions = make([]appconfig.CustomAction, len(opts.CustomActions))
		for i, ca := range opts.CustomActions {
			s.cfg.CustomActions[i] = appconfig.CustomAction{
				ID:          ca.ID,
				Title:       ca.Title,
				Kind:        ca.Kind,
				Scope:       ca.Scope,
				Instruction: ca.Instruction,
				System:      ca.System,
				User:        ca.User,
			}
		}
	}
	s.llmClient = opts.Client
	if opts.Client != nil {
		s.llmProvider = canonicalProvider(opts.Client.Name())
	} else {
		s.llmProvider = canonicalProvider(s.cfg.Provider)
	}
	s.altClients = make(map[string]llm.Client)
	if opts.IgnoreChecker != nil {
		s.ignoreChecker = opts.IgnoreChecker
	}
}

// ApplyOptions updates the server's configuration at runtime.
func (s *Server) ApplyOptions(opts ServerOptions) {
	s.applyOptions(opts)
}

func (s *Server) currentLLMClient() llm.Client {
	s.mu.RLock()
	defer s.mu.RUnlock()
	return s.llmClient
}

func newClientForProvider(cfg appconfig.App, provider string) (llm.Client, error) {
	llmCfg := llm.Config{
		Provider:              provider,
		RequestTimeout:        cfg.RequestTimeout,
		OpenAIBaseURL:         cfg.OpenAIBaseURL,
		OpenAIModel:           cfg.OpenAIModel,
		OpenAITemperature:     cfg.OpenAITemperature,
		OpenRouterBaseURL:     cfg.OpenRouterBaseURL,
		OpenRouterModel:       cfg.OpenRouterModel,
		OpenRouterTemperature: cfg.OpenRouterTemperature,
		OllamaBaseURL:         cfg.OllamaBaseURL,
		OllamaModel:           cfg.OllamaModel,
		OllamaTemperature:     cfg.OllamaTemperature,
		AnthropicBaseURL:      cfg.AnthropicBaseURL,
		AnthropicModel:        cfg.AnthropicModel,
		AnthropicTemperature:  cfg.AnthropicTemperature,
	}
	oaKey := strings.TrimSpace(os.Getenv("HEXAI_OPENAI_API_KEY"))
	if oaKey == "" {
		oaKey = strings.TrimSpace(os.Getenv("OPENAI_API_KEY"))
	}
	orKey := strings.TrimSpace(os.Getenv("HEXAI_OPENROUTER_API_KEY"))
	if orKey == "" {
		orKey = strings.TrimSpace(os.Getenv("OPENROUTER_API_KEY"))
	}
	anKey := strings.TrimSpace(os.Getenv("HEXAI_ANTHROPIC_API_KEY"))
	if anKey == "" {
		anKey = strings.TrimSpace(os.Getenv("ANTHROPIC_API_KEY"))
	}
	return llm.NewFromConfig(llmCfg, oaKey, orKey, anKey)
}

func (s *Server) clientFor(spec requestSpec) llm.Client {
	provider := canonicalProvider(spec.provider)
	s.mu.RLock()
	baseProvider := s.llmProvider
	baseClient := s.llmClient
	if baseClient != nil && strings.TrimSpace(baseProvider) == "" {
		baseProvider = canonicalProvider(baseClient.Name())
	}
	if provider == "" {
		provider = baseProvider
	}
	if provider == baseProvider && baseClient != nil {
		s.mu.RUnlock()
		return baseClient
	}
	if c, ok := s.altClients[provider]; ok {
		s.mu.RUnlock()
		return c
	}
	cfg := s.cfg
	store := s.configStore
	s.mu.RUnlock()
	if store != nil {
		cfg = store.Snapshot()
	}
	cfg.Provider = provider
	modelOverride := strings.TrimSpace(spec.entry.Model)
	switch provider {
	case "openai":
		if modelOverride != "" {
			cfg.OpenAIModel = modelOverride
		} else if spec.fallbackModel != "" {
			cfg.OpenAIModel = spec.fallbackModel
		}
	case "openrouter":
		if modelOverride != "" {
			cfg.OpenRouterModel = modelOverride
		} else if spec.fallbackModel != "" {
			cfg.OpenRouterModel = spec.fallbackModel
		}
	case "ollama":
		if modelOverride != "" {
			cfg.OllamaModel = modelOverride
		} else if spec.fallbackModel != "" {
			cfg.OllamaModel = spec.fallbackModel
		}
	case "anthropic":
		if modelOverride != "" {
			cfg.AnthropicModel = modelOverride
		} else if spec.fallbackModel != "" {
			cfg.AnthropicModel = spec.fallbackModel
		}
	}
	client, err := newClientForProvider(cfg, provider)
	if err != nil {
		logging.Logf("lsp ", "failed to build client for provider=%s: %v", provider, err)
		if baseClient != nil {
			return baseClient
		}
		return nil
	}
	s.mu.Lock()
	defer s.mu.Unlock()
	if provider == s.llmProvider {
		if s.llmClient == nil {
			s.llmClient = client
			s.llmProvider = provider
		}
		return s.llmClient
	}
	if existing, ok := s.altClients[provider]; ok {
		return existing
	}
	if s.altClients == nil {
		s.altClients = make(map[string]llm.Client)
	}
	s.altClients[provider] = client
	return client
}

func (s *Server) currentConfig() appconfig.App {
	if s.configStore != nil {
		return s.configStore.Snapshot()
	}
	s.mu.RLock()
	defer s.mu.RUnlock()
	return s.cfg
}

func (s *Server) storePendingCompletion(key string, items []CompletionItem) {
	if len(items) == 0 {
		return
	}
	cpy := make([]CompletionItem, len(items))
	copy(cpy, items)
	s.mu.Lock()
	if s.pendingCompletions == nil {
		s.pendingCompletions = make(map[string][]CompletionItem)
	}
	s.pendingCompletions[key] = cpy
	s.mu.Unlock()
}

func (s *Server) setCompletionsDisabled(disabled bool) bool {
	s.mu.Lock()
	prev := s.completionsDisabled
	s.completionsDisabled = disabled
	s.mu.Unlock()
	return prev
}

func (s *Server) completionDisabled() bool {
	s.mu.RLock()
	defer s.mu.RUnlock()
	return s.completionsDisabled
}

func (s *Server) takePendingCompletion(key string) []CompletionItem {
	s.mu.Lock()
	defer s.mu.Unlock()
	if len(s.pendingCompletions) == 0 {
		return nil
	}
	items, ok := s.pendingCompletions[key]
	if !ok {
		return nil
	}
	delete(s.pendingCompletions, key)
	cpy := make([]CompletionItem, len(items))
	copy(cpy, items)
	return cpy
}

func (s *Server) maxTokens() int {
	cfg := s.currentConfig()
	if cfg.MaxTokens <= 0 {
		return 500
	}
	return cfg.MaxTokens
}

func (s *Server) contextMode() string {
	mode := strings.TrimSpace(s.currentConfig().ContextMode)
	if mode == "" {
		return "file-on-new-func"
	}
	return mode
}

func (s *Server) windowLines() int {
	cfg := s.currentConfig()
	if cfg.ContextWindowLines <= 0 {
		return 120
	}
	return cfg.ContextWindowLines
}

func (s *Server) maxContextTokens() int {
	cfg := s.currentConfig()
	if cfg.MaxContextTokens <= 0 {
		return 2000
	}
	return cfg.MaxContextTokens
}

func (s *Server) triggerCharacters() []string {
	cfg := s.currentConfig()
	if len(cfg.TriggerCharacters) == 0 {
		return []string{".", ":", "/", "_", ")", "{"}
	}
	return append([]string{}, cfg.TriggerCharacters...)
}

func (s *Server) codingTemperature() *float64 {
	cfg := s.currentConfig()
	return cfg.CodingTemperature
}

func (s *Server) manualInvokeMinPrefix() int {
	return s.currentConfig().ManualInvokeMinPrefix
}

func (s *Server) completionDebounce() time.Duration {
	cfg := s.currentConfig()
	if cfg.CompletionDebounceMs <= 0 {
		return 0
	}
	return time.Duration(cfg.CompletionDebounceMs) * time.Millisecond
}

func (s *Server) completionThrottle() time.Duration {
	cfg := s.currentConfig()
	if cfg.CompletionThrottleMs <= 0 {
		return 0
	}
	return time.Duration(cfg.CompletionThrottleMs) * time.Millisecond
}

func (s *Server) completionWaitAll() bool {
	cfg := s.currentConfig()
	if cfg.CompletionWaitAll == nil {
		return true // default: wait for all backends
	}
	return *cfg.CompletionWaitAll
}

func (s *Server) inlineMarkers() (open string, close string, openChar byte, closeChar byte) {
	cfg := s.currentConfig()
	open = strings.TrimSpace(cfg.InlineOpen)
	if open == "" {
		open = ">!"
	}
	close = strings.TrimSpace(cfg.InlineClose)
	if close == "" {
		close = ">"
	}
	openChar = '>'
	if len(open) > 0 {
		openChar = open[0]
	}
	closeChar = '>'
	if len(close) > 0 {
		closeChar = close[0]
	}
	return open, close, openChar, closeChar
}

func (s *Server) chatConfig() (suffix string, prefixes []string, suffixChar byte) {
	cfg := s.currentConfig()
	suffix = cfg.ChatSuffix
	if suffix != "" {
		suffix = strings.TrimSpace(suffix)
		if suffix == "" {
			suffix = ">"
		}
	} else {
		suffix = ""
	}
	if len(cfg.ChatPrefixes) == 0 {
		prefixes = []string{"?", "!", ":", ";"}
	} else {
		prefixes = append([]string{}, cfg.ChatPrefixes...)
	}
	suffixChar = '>'
	if len(suffix) > 0 {
		suffixChar = suffix[0]
	}
	return suffix, prefixes, suffixChar
}

func (s *Server) promptSet() appconfig.App {
	return s.currentConfig()
}

func (s *Server) customActions() []CustomAction {
	cfg := s.currentConfig()
	if len(cfg.CustomActions) == 0 {
		return nil
	}
	customs := make([]CustomAction, 0, len(cfg.CustomActions))
	for _, ca := range cfg.CustomActions {
		customs = append(customs, CustomAction{
			ID:          ca.ID,
			Title:       ca.Title,
			Kind:        ca.Kind,
			Scope:       ca.Scope,
			Instruction: ca.Instruction,
			System:      ca.System,
			User:        ca.User,
		})
	}
	return customs
}

func (s *Server) Run() error {
	for {
		body, err := s.readMessage()
		if err == io.EOF {
			return nil
		}
		if err != nil {
			return err
		}
		var req Request
		if err := json.Unmarshal(body, &req); err != nil {
			logging.Logf("lsp ", "invalid JSON: %v", err)
			continue
		}
		if req.Method == "" {
			// A response from client; ignore
			continue
		}
		go s.handle(req)
		if s.exited {
			return nil
		}
	}
}