// Copyright 2018 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 (
	"context"
	"strings"

	"golang.org/x/tools/internal/lsp/protocol"
	"golang.org/x/tools/internal/lsp/source"
	"golang.org/x/tools/internal/lsp/telemetry"
	"golang.org/x/tools/internal/span"
	"golang.org/x/tools/internal/telemetry/log"
	"golang.org/x/tools/internal/telemetry/trace"
	errors "golang.org/x/xerrors"
)

func (s *Server) diagnostics(view source.View, uri span.URI) error {
	ctx := view.BackgroundContext()
	ctx, done := trace.StartSpan(ctx, "lsp:background-worker")
	defer done()

	ctx = telemetry.File.With(ctx, uri)

	f, err := view.GetFile(ctx, uri)
	if err != nil {
		return err
	}
	// For non-Go files, don't return any diagnostics.
	gof, ok := f.(source.GoFile)
	if !ok {
		return errors.Errorf("%s is not a Go file", f.URI())
	}
	reports, warningMsg, err := source.Diagnostics(ctx, view, gof, view.Options().DisabledAnalyses)
	if err != nil {
		return err
	}
	if warningMsg != "" {
		s.client.ShowMessage(ctx, &protocol.ShowMessageParams{
			Type:    protocol.Info,
			Message: warningMsg,
		})
	}

	s.undeliveredMu.Lock()
	defer s.undeliveredMu.Unlock()

	for uri, diagnostics := range reports {
		if err := s.publishDiagnostics(ctx, uri, diagnostics); err != nil {
			if s.undelivered == nil {
				s.undelivered = make(map[span.URI][]source.Diagnostic)
			}
			s.undelivered[uri] = diagnostics

			log.Error(ctx, "failed to deliver diagnostic (will retry)", err, telemetry.File)
			continue
		}
		// In case we had old, undelivered diagnostics.
		delete(s.undelivered, uri)
	}
	// Anytime we compute diagnostics, make sure to also send along any
	// undelivered ones (only for remaining URIs).
	for uri, diagnostics := range s.undelivered {
		if err := s.publishDiagnostics(ctx, uri, diagnostics); err != nil {
			log.Error(ctx, "failed to deliver diagnostic for (will not retry)", err, telemetry.File)
		}

		// If we fail to deliver the same diagnostics twice, just give up.
		delete(s.undelivered, uri)
	}
	return nil
}

func (s *Server) publishDiagnostics(ctx context.Context, uri span.URI, diagnostics []source.Diagnostic) error {
	s.client.PublishDiagnostics(ctx, &protocol.PublishDiagnosticsParams{
		Diagnostics: toProtocolDiagnostics(ctx, diagnostics),
		URI:         protocol.NewURI(uri),
	})
	return nil
}

func toProtocolDiagnostics(ctx context.Context, diagnostics []source.Diagnostic) []protocol.Diagnostic {
	reports := []protocol.Diagnostic{}
	for _, diag := range diagnostics {
		reports = append(reports, toProtocolDiagnostic(ctx, diag))
	}
	return reports
}

func toProtocolDiagnostic(ctx context.Context, diag source.Diagnostic) protocol.Diagnostic {
	var severity protocol.DiagnosticSeverity
	switch diag.Severity {
	case source.SeverityError:
		severity = protocol.SeverityError
	case source.SeverityWarning:
		severity = protocol.SeverityWarning
	}
	return protocol.Diagnostic{
		Message:  strings.TrimSpace(diag.Message), // go list returns errors prefixed by newline
		Range:    diag.Range,
		Severity: severity,
		Source:   diag.Source,
		Tags:     diag.Tags,
	}
}