// Copyright 2019 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package lsp

import (
	"bytes"
	"context"

	"golang.org/x/tools/internal/jsonrpc2"
	"golang.org/x/tools/internal/lsp/protocol"
	"golang.org/x/tools/internal/span"
)

func (s *Server) didChange(ctx context.Context, params *protocol.DidChangeTextDocumentParams) error {
	if len(params.ContentChanges) < 1 {
		return jsonrpc2.NewErrorf(jsonrpc2.CodeInternalError, "no content changes provided")
	}

	var text string
	switch s.textDocumentSyncKind {
	case protocol.Incremental:
		var err error
		text, err = s.applyChanges(ctx, params)
		if err != nil {
			return err
		}
	case protocol.Full:
		// We expect the full content of file, i.e. a single change with no range.
		change := params.ContentChanges[0]
		if change.RangeLength != 0 {
			return jsonrpc2.NewErrorf(jsonrpc2.CodeInternalError, "unexpected change range provided")
		}
		text = change.Text
	}
	return s.cacheAndDiagnose(ctx, span.NewURI(params.TextDocument.URI), text)
}

func (s *Server) applyChanges(ctx context.Context, params *protocol.DidChangeTextDocumentParams) (string, error) {
	if len(params.ContentChanges) == 1 && params.ContentChanges[0].Range == nil {
		// If range is empty, we expect the full content of file, i.e. a single change with no range.
		change := params.ContentChanges[0]
		if change.RangeLength != 0 {
			return "", jsonrpc2.NewErrorf(jsonrpc2.CodeInternalError, "unexpected change range provided")
		}
		return change.Text, nil
	}

	uri := span.NewURI(params.TextDocument.URI)
	view := s.findView(ctx, uri)
	file, m, err := newColumnMap(ctx, view, uri)
	if err != nil {
		return "", jsonrpc2.NewErrorf(jsonrpc2.CodeInternalError, "file not found")
	}
	content := file.GetContent(ctx)
	for _, change := range params.ContentChanges {
		spn, err := m.RangeSpan(*change.Range)
		if err != nil {
			return "", err
		}
		if !spn.HasOffset() {
			return "", jsonrpc2.NewErrorf(jsonrpc2.CodeInternalError, "invalid range for content change")
		}
		start, end := spn.Start().Offset(), spn.End().Offset()
		if end < start {
			return "", jsonrpc2.NewErrorf(jsonrpc2.CodeInternalError, "invalid range for content change")
		}
		var buf bytes.Buffer
		buf.Write(content[:start])
		buf.WriteString(change.Text)
		buf.Write(content[end:])
		content = buf.Bytes()
	}
	return string(content), nil
}

func (s *Server) didSave(ctx context.Context, params *protocol.DidSaveTextDocumentParams) error {
	return nil // ignore
}

func (s *Server) didClose(ctx context.Context, params *protocol.DidCloseTextDocumentParams) error {
	uri := span.NewURI(params.TextDocument.URI)
	view := s.findView(ctx, uri)
	return view.SetContent(ctx, uri, nil)
}