// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
// SPDX-License-Identifier: BSD-3-Clause

// Package lsp implements a Language Server Protocol server for GAsm.  It
// speaks JSON-RPC 2.0 over any io.Reader/io.Writer pair (normally standard
// input/output) and provides completion, hover documentation, document
// symbols, diagnostics and semantic-token highlighting — all backed by the
// pure-Go lexer, parser, arch and lint packages.  It is the vendor-neutral
// integration point: any LSP-capable editor can use it with no editor-specific
// plugin code.
package lsp

import "encoding/json"

// --- JSON-RPC 2.0 -----------------------------------------------------------

// rpcMessage is the common envelope for every JSON-RPC message.
type rpcMessage struct {
	JSONRPC string           `json:"jsonrpc"`
	ID      *json.RawMessage `json:"id,omitempty"`
	Method  string           `json:"method,omitempty"`
	Params  json.RawMessage  `json:"params,omitempty"`
	Result  any              `json:"result,omitempty"`
	Error   *rpcError        `json:"error,omitempty"`
}

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

// JSON-RPC error codes used by LSP.
const (
	errParse          = -32700
	errInvalidRequest = -32600
	errMethodNotFound = -32601
	errInvalidParams  = -32602
	errInternal       = -32603
)

// --- LSP positions and ranges ----------------------------------------------

// Position is a zero-based line/character position, as LSP requires.
type Position struct {
	Line      int `json:"line"`
	Character int `json:"character"`
}

// Range is a pair of positions.
type Range struct {
	Start Position `json:"start"`
	End   Position `json:"end"`
}

// Location is a range within a document URI.
type Location struct {
	URI   string `json:"uri"`
	Range Range  `json:"range"`
}

// --- diagnostics ------------------------------------------------------------

// Diagnostic severities (LSP ordering: 1 = error).
const (
	sevError       = 1
	sevWarning     = 2
	sevInformation = 3
	sevHint        = 4
)

// Diagnostic is one published finding.
type Diagnostic struct {
	Range    Range  `json:"range"`
	Severity int    `json:"severity"`
	Code     string `json:"code,omitempty"`
	Source   string `json:"source,omitempty"`
	Message  string `json:"message"`
}

type publishDiagnosticsParams struct {
	URI         string       `json:"uri"`
	Diagnostics []Diagnostic `json:"diagnostics"`
}

// --- text document synchronisation -----------------------------------------

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

type didOpenParams struct {
	TextDocument textDocumentItem `json:"textDocument"`
}

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

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

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

type didChangeParams struct {
	TextDocument   versionedTextDocumentIdentifier `json:"textDocument"`
	ContentChanges []contentChangeEvent            `json:"contentChanges"`
}

type didCloseParams struct {
	TextDocument textDocumentIdentifier `json:"textDocument"`
}

// --- completion -------------------------------------------------------------

// Completion item kinds (a useful subset).
const (
	ciFunction = 3
	ciField    = 5
	ciVariable = 6
	ciClass    = 7
	ciModule   = 9
	ciKeyword  = 14
	ciConstant = 21
	ciStruct   = 22
)

// CompletionItem is one completion suggestion.
type CompletionItem struct {
	Label         string `json:"label"`
	Kind          int    `json:"kind,omitempty"`
	Detail        string `json:"detail,omitempty"`
	Documentation string `json:"documentation,omitempty"`
	InsertText    string `json:"insertText,omitempty"`
}

type completionParams struct {
	TextDocument textDocumentIdentifier `json:"textDocument"`
	Position     Position               `json:"position"`
}

// --- hover ------------------------------------------------------------------

type hoverParams struct {
	TextDocument textDocumentIdentifier `json:"textDocument"`
	Position     Position               `json:"position"`
}

type definitionParams struct {
	TextDocument textDocumentIdentifier `json:"textDocument"`
	Position     Position               `json:"position"`
}

// Hover is the hover response.
type Hover struct {
	Contents markupContent `json:"contents"`
	Range    Range         `json:"range,omitempty"`
}

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

// --- document symbols -------------------------------------------------------

// Symbol kinds (a useful subset).
const (
	symFunction = 12
	symConstant = 14
	symVariable = 13
)

// DocumentSymbol is a hierarchical symbol.
type DocumentSymbol struct {
	Name           string           `json:"name"`
	Detail         string           `json:"detail,omitempty"`
	Kind           int              `json:"kind"`
	Range          Range            `json:"range"`
	SelectionRange Range            `json:"selectionRange"`
	Children       []DocumentSymbol `json:"children,omitempty"`
}

type documentSymbolParams struct {
	TextDocument textDocumentIdentifier `json:"textDocument"`
}

// --- semantic tokens --------------------------------------------------------

// semanticTokenTypes is the legend of token type names, in index order.  The
// indices are referenced by the encoder below.
var semanticTokenTypes = []string{
	"comment",   // 0
	"keyword",   // 1
	"function",  // 2
	"variable",  // 3
	"type",      // 4
	"number",    // 5
	"string",    // 6
	"operator",  // 7
	"property",  // 8
	"namespace", // 9
	"macro",     // 10
}

const (
	stComment   = 0
	stKeyword   = 1
	stFunction  = 2
	stVariable  = 3
	stType      = 4
	stNumber    = 5
	stString    = 6
	stOperator  = 7
	stProperty  = 8
	stNamespace = 9
	stMacro     = 10
)

// SemanticTokensLegend advertises the token classification.
type SemanticTokensLegend struct {
	TokenTypes     []string `json:"tokenTypes"`
	TokenModifiers []string `json:"tokenModifiers"`
}

// SemanticTokens is the encoded token payload.
type SemanticTokens struct {
	Data []int `json:"data"`
}

type semanticTokensParams struct {
	TextDocument textDocumentIdentifier `json:"textDocument"`
}

// --- initialize -------------------------------------------------------------

type initializeParams struct {
	RootURI string `json:"rootUri"`
}

// ServerCapabilities advertises what this server provides.
type ServerCapabilities struct {
	TextDocumentSync       int            `json:"textDocumentSync"`
	CompletionProvider     map[string]any `json:"completionProvider,omitempty"`
	HoverProvider          bool           `json:"hoverProvider,omitempty"`
	DocumentSymbolProvider bool           `json:"documentSymbolProvider,omitempty"`
	SemanticTokensProvider map[string]any `json:"semanticTokensProvider,omitempty"`
	DiagnosticProvider     map[string]any `json:"diagnosticProvider,omitempty"`
}

type initializeResult struct {
	Capabilities ServerCapabilities `json:"capabilities"`
	ServerInfo   map[string]string  `json:"serverInfo,omitempty"`
}