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

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

	"codeberg.org/snonux/hexai/internal/llm"
	"codeberg.org/snonux/hexai/internal/logging"
)

// Server implements a minimal LSP over stdio.
type Server struct {
	in               *bufio.Reader
	out              io.Writer
	logger           *log.Logger
	exited           bool
	mu               sync.RWMutex
	docs             map[string]*document
	logContext       bool
	llmClient        llm.Client
	lastInput        time.Time
	maxTokens        int
	contextMode      string
	windowLines      int
	maxContextTokens int
	triggerChars     []string
	// If set, used as the LSP coding temperature for all LLM calls
	codingTemperature *float64
	// 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
	// Outgoing JSON-RPC id counter for server-initiated requests
	nextID int64
	// Minimum identifier chars required for manual invoke to bypass prefix checks
	manualInvokeMinPrefix int

	// Debounce and throttle settings
	completionDebounce time.Duration
	throttleInterval   time.Duration
	lastLLMCall        time.Time

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

	// Configurable trigger characters
	inlineOpen   string
	inlineClose  string
	chatSuffix   string
	chatPrefixes []string

	// Prompt templates
	// Completion
	promptCompSysGeneral  string
	promptCompSysParams   string
	promptCompSysInline   string
	promptCompUserGeneral string
	promptCompUserParams  string
	promptCompExtraHeader string
	// Provider-native code completion
	promptNativeCompletion string
	// In-editor chat
	promptChatSystem string
	// Code actions
	promptRewriteSystem     string
	promptDiagnosticsSystem string
	promptDocumentSystem    string
	promptRewriteUser       string
	promptDiagnosticsUser   string
    promptDocumentUser      string
    promptGoTestSystem      string
    promptGoTestUser        string
    promptSimplifySystem    string
    promptSimplifyUser      string
}

// ServerOptions collects configuration for NewServer to avoid long parameter lists.
type ServerOptions struct {
	LogContext       bool
	MaxTokens        int
	ContextMode      string
	WindowLines      int
	MaxContextTokens int

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

	// 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
}

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}
	maxTokens := opts.MaxTokens
	if maxTokens <= 0 {
		maxTokens = 500
	}
	s.maxTokens = maxTokens
	contextMode := opts.ContextMode
	if contextMode == "" {
		contextMode = "file-on-new-func"
	}
	windowLines := opts.WindowLines
	if windowLines <= 0 {
		windowLines = 120
	}
	maxContextTokens := opts.MaxContextTokens
	if maxContextTokens <= 0 {
		maxContextTokens = 2000
	}
	s.contextMode = contextMode
	s.windowLines = windowLines
	s.maxContextTokens = maxContextTokens

	s.startTime = time.Now()
	s.llmClient = opts.Client
	if len(opts.TriggerCharacters) == 0 {
		// Defaults (no space to avoid auto-trigger after whitespace)
		s.triggerChars = []string{".", ":", "/", "_", ")", "{"}
	} else {
		s.triggerChars = append([]string{}, opts.TriggerCharacters...)
	}
	s.codingTemperature = opts.CodingTemperature
	s.compCache = make(map[string]string)
	s.manualInvokeMinPrefix = opts.ManualInvokeMinPrefix
	if opts.CompletionDebounceMs > 0 {
		s.completionDebounce = time.Duration(opts.CompletionDebounceMs) * time.Millisecond
	}
	if opts.CompletionThrottleMs > 0 {
		s.throttleInterval = time.Duration(opts.CompletionThrottleMs) * time.Millisecond
	}
	// Trigger character config (with sane defaults if missing)
	if strings.TrimSpace(opts.InlineOpen) == "" {
		s.inlineOpen = ">"
	} else {
		s.inlineOpen = opts.InlineOpen
	}
	if strings.TrimSpace(opts.InlineClose) == "" {
		s.inlineClose = ">"
	} else {
		s.inlineClose = opts.InlineClose
	}
	if strings.TrimSpace(opts.ChatSuffix) == "" {
		s.chatSuffix = ">"
	} else {
		s.chatSuffix = opts.ChatSuffix
	}
	if len(opts.ChatPrefixes) == 0 {
		s.chatPrefixes = []string{"?", "!", ":", ";"}
	} else {
		s.chatPrefixes = append([]string{}, opts.ChatPrefixes...)
	}

	// Prompts
	s.promptCompSysGeneral = opts.PromptCompSysGeneral
	s.promptCompSysParams = opts.PromptCompSysParams
	s.promptCompSysInline = opts.PromptCompSysInline
	s.promptCompUserGeneral = opts.PromptCompUserGeneral
	s.promptCompUserParams = opts.PromptCompUserParams
	s.promptCompExtraHeader = opts.PromptCompExtraHeader
	s.promptNativeCompletion = opts.PromptNativeCompletion
	s.promptChatSystem = opts.PromptChatSystem
	s.promptRewriteSystem = opts.PromptRewriteSystem
	s.promptDiagnosticsSystem = opts.PromptDiagnosticsSystem
	s.promptDocumentSystem = opts.PromptDocumentSystem
	s.promptRewriteUser = opts.PromptRewriteUser
	s.promptDiagnosticsUser = opts.PromptDiagnosticsUser
    s.promptDocumentUser = opts.PromptDocumentUser
    s.promptGoTestSystem = opts.PromptGoTestSystem
    s.promptGoTestUser = opts.PromptGoTestUser
    s.promptSimplifySystem = opts.PromptSimplifySystem
    s.promptSimplifyUser = opts.PromptSimplifyUser

	// Assign package-level inline trigger chars for free helper functions
	if s.inlineOpen != "" {
		inlineOpenChar = s.inlineOpen[0]
	}
	if s.inlineClose != "" {
		inlineCloseChar = s.inlineClose[0]
	}
	if s.chatSuffix != "" {
		chatSuffixChar = s.chatSuffix[0]
	}
	if len(s.chatPrefixes) > 0 {
		chatPrefixSingles = append([]string{}, s.chatPrefixes...)
	}
	// 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) 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
		}
	}
}