package lsp

import (
	"bufio"
	"encoding/json"
	"fmt"
	"io"
	"os"
	"strings"

	"github.com/marte-dev/marte-dev-tools/internal/index"
	"github.com/marte-dev/marte-dev-tools/internal/parser"
)

type JsonRpcMessage struct {
	Jsonrpc string          `json:"jsonrpc"`
	Method  string          `json:"method,omitempty"`
	Params  json.RawMessage `json:"params,omitempty"`
	ID      interface{}     `json:"id,omitempty"`
	Result  interface{}     `json:"result,omitempty"`
	Error   *JsonRpcError   `json:"error,omitempty"`
}

type JsonRpcError struct {
	Code    int    `json:"code"`
	Message string `json:"message"`
}

type DidOpenTextDocumentParams struct {
	TextDocument TextDocumentItem `json:"textDocument"`
}

type DidChangeTextDocumentParams struct {
	TextDocument   VersionedTextDocumentIdentifier `json:"textDocument"`
	ContentChanges []TextDocumentContentChangeEvent `json:"contentChanges"`
}

type TextDocumentItem struct {
	URI        string `json:"uri"`
	LanguageID string `json:"languageId"`
	Version    int    `json:"version"`
	Text       string `json:"text"`
}

type VersionedTextDocumentIdentifier struct {
	URI     string `json:"uri"`
	Version int    `json:"version"`
}

type TextDocumentContentChangeEvent struct {
	Text string `json:"text"`
}

type HoverParams struct {
	TextDocument TextDocumentIdentifier `json:"textDocument"`
	Position     Position               `json:"position"`
}

type TextDocumentIdentifier struct {
	URI string `json:"uri"`
}

type Position struct {
	Line      int `json:"line"`
	Character int `json:"character"`
}

type Hover struct {
	Contents interface{} `json:"contents"`
}

type MarkupContent struct {
	Kind  string `json:"kind"`
	Value string `json:"value"`
}

var tree = index.NewProjectTree()

func RunServer() {
	reader := bufio.NewReader(os.Stdin)
	for {
		msg, err := readMessage(reader)
		if err != nil {
			if err == io.EOF {
				break
			}
			fmt.Fprintf(os.Stderr, "Error reading message: %v\n", err)
			continue
		}

		handleMessage(msg)
	}
}

func readMessage(reader *bufio.Reader) (*JsonRpcMessage, error) {
	var contentLength int
	for {
		line, err := reader.ReadString('\n')
		if err != nil {
			return nil, err
		}
		if line == "\r\n" {
			break
		}
		if _, err := fmt.Sscanf(line, "Content-Length: %d", &contentLength); err == nil {
			continue
		}
	}

	body := make([]byte, contentLength)
	_, err := io.ReadFull(reader, body)
	if err != nil {
		return nil, err
	}

	var msg JsonRpcMessage
	err = json.Unmarshal(body, &msg)
	return &msg, err
}

func handleMessage(msg *JsonRpcMessage) {
	switch msg.Method {
	case "initialize":
		respond(msg.ID, map[string]interface{}{
			"capabilities": map[string]interface{}{
				"textDocumentSync": 1, // Full sync
				"hoverProvider":    true,
				"definitionProvider": true,
				"referencesProvider": true,
			},
		})
	case "initialized":
		// Do nothing
	case "shutdown":
		respond(msg.ID, nil)
	case "exit":
		os.Exit(0)
	case "textDocument/didOpen":
		var params DidOpenTextDocumentParams
		if err := json.Unmarshal(msg.Params, &params); err == nil {
			handleDidOpen(params)
		}
	case "textDocument/didChange":
		var params DidChangeTextDocumentParams
		if err := json.Unmarshal(msg.Params, &params); err == nil {
			handleDidChange(params)
		}
	case "textDocument/hover":
		var params HoverParams
		if err := json.Unmarshal(msg.Params, &params); err == nil {
			res := handleHover(params)
			respond(msg.ID, res)
		} else {
			respond(msg.ID, nil)
		}
	}
}

func uriToPath(uri string) string {
	return strings.TrimPrefix(uri, "file://")
}

func handleDidOpen(params DidOpenTextDocumentParams) {
	path := uriToPath(params.TextDocument.URI)
	p := parser.NewParser(params.TextDocument.Text)
	config, err := p.Parse()
	if err == nil {
		tree.AddFile(path, config)
		tree.ResolveReferences()
	}
}

func handleDidChange(params DidChangeTextDocumentParams) {
	if len(params.ContentChanges) == 0 {
		return
	}
	// Full sync: text is in ContentChanges[0].Text
	text := params.ContentChanges[0].Text
	path := uriToPath(params.TextDocument.URI)
	p := parser.NewParser(text)
	config, err := p.Parse()
	if err == nil {
		tree.AddFile(path, config)
		tree.ResolveReferences()
	}
}

func handleHover(params HoverParams) *Hover {
	path := uriToPath(params.TextDocument.URI)
	// LSP 0-based to Parser 1-based
	line := params.Position.Line + 1
	col := params.Position.Character + 1
	
	res := tree.Query(path, line, col)
	if res == nil {
		return nil
	}
	
	var content string
	
	if res.Node != nil {
		// Try to find Class field
		class := "Unknown"
		for _, frag := range res.Node.Fragments {
			for _, def := range frag.Definitions {
				if f, ok := def.(*parser.Field); ok && f.Name == "Class" {
					if s, ok := f.Value.(*parser.StringValue); ok {
						class = s.Value
					} else if r, ok := f.Value.(*parser.ReferenceValue); ok {
						class = r.Value
					}
				}
			}
		}
		content = fmt.Sprintf("**Object**: `%s`\n\n**Class**: `%s`", res.Node.RealName, class)
	} else if res.Field != nil {
		content = fmt.Sprintf("**Field**: `%s`", res.Field.Name)
	} else if res.Reference != nil {
		targetName := "Unresolved"
		if res.Reference.Target != nil {
			targetName = res.Reference.Target.RealName
		}
		content = fmt.Sprintf("**Reference**: `%s` -> `%s`", res.Reference.Name, targetName)
	}
	
	if content == "" {
		return nil
	}
	
	return &Hover{
		Contents: MarkupContent{
			Kind:  "markdown",
			Value: content,
		},
	}
}

func respond(id interface{}, result interface{}) {
	msg := JsonRpcMessage{
		Jsonrpc: "2.0",
		ID:      id,
		Result:  result,
	}
	send(msg)
}

func send(msg interface{}) {
	body, _ := json.Marshal(msg)
	fmt.Printf("Content-Length: %d\r\n\r\n%s", len(body), body)
}