// 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"
	"crypto/sha1"
	"fmt"
	"strings"
	"sync"

	"golang.org/x/tools/internal/event"
	"golang.org/x/tools/internal/lsp/debug/tag"
	"golang.org/x/tools/internal/lsp/mod"
	"golang.org/x/tools/internal/lsp/protocol"
	"golang.org/x/tools/internal/lsp/source"
	"golang.org/x/tools/internal/xcontext"
	"golang.org/x/xerrors"
)

// idWithAnalysis is used to track if the diagnostics for a given file were
// computed with analyses.
type idWithAnalysis struct {
	id           source.FileIdentity
	withAnalysis bool
}

func (s *Server) diagnoseDetached(snapshot source.Snapshot) {
	ctx := snapshot.View().BackgroundContext()
	ctx = xcontext.Detach(ctx)
	reports, shows := s.diagnose(ctx, snapshot, false)
	if shows != nil {
		// If a view has been created or the configuration changed, warn the user.
		s.client.ShowMessage(ctx, shows)
	}
	s.publishReports(ctx, snapshot, reports)
}

func (s *Server) diagnoseSnapshot(snapshot source.Snapshot) {
	ctx := snapshot.View().BackgroundContext()

	// Ignore possible workspace configuration warnings in the normal flow.
	reports, _ := s.diagnose(ctx, snapshot, false)
	s.publishReports(ctx, snapshot, reports)
}

// diagnose is a helper function for running diagnostics with a given context.
// Do not call it directly.
func (s *Server) diagnose(ctx context.Context, snapshot source.Snapshot, alwaysAnalyze bool) (map[idWithAnalysis]map[string]*source.Diagnostic, *protocol.ShowMessageParams) {
	ctx, done := event.Start(ctx, "lsp:background-worker")
	defer done()

	// Wait for a free diagnostics slot.
	select {
	case <-ctx.Done():
		return nil, nil
	case s.diagnosticsSema <- struct{}{}:
	}
	defer func() { <-s.diagnosticsSema }()

	var reportsMu sync.Mutex
	reports := map[idWithAnalysis]map[string]*source.Diagnostic{}

	// First, diagnose the go.mod file.
	modReports, modErr := mod.Diagnostics(ctx, snapshot)
	if ctx.Err() != nil {
		return nil, nil
	}
	if modErr != nil {
		event.Error(ctx, "warning: diagnose go.mod", modErr, tag.Directory.Of(snapshot.View().Folder().Filename()))
	}
	for id, diags := range modReports {
		if id.URI == "" {
			event.Error(ctx, "missing URI for module diagnostics", fmt.Errorf("empty URI"), tag.Directory.Of(snapshot.View().Folder().Filename()))
			continue
		}
		key := idWithAnalysis{
			id:           id,
			withAnalysis: true, // treat go.mod diagnostics like analyses
		}
		if _, ok := reports[key]; !ok {
			reports[key] = map[string]*source.Diagnostic{}
		}
		for _, d := range diags {
			reports[key][diagnosticKey(d)] = d
		}
	}

	// Diagnose all of the packages in the workspace.
	wsPackages, err := snapshot.WorkspacePackages(ctx)
	if err != nil {
		// Try constructing a more helpful error message out of this error.
		if s.handleFatalErrors(ctx, snapshot, modErr, err) {
			return nil, nil
		}
		msg := `The code in the workspace failed to compile (see the error message below).
If you believe this is a mistake, please file an issue: https://github.com/golang/go/issues/new.`
		event.Error(ctx, msg, err, tag.Snapshot.Of(snapshot.ID()), tag.Directory.Of(snapshot.View().Folder()))
		if err := s.client.ShowMessage(ctx, &protocol.ShowMessageParams{
			Type:    protocol.Error,
			Message: fmt.Sprintf("%s\n%v", msg, err),
		}); err != nil {
			event.Error(ctx, "ShowMessage failed", err, tag.Directory.Of(snapshot.View().Folder().Filename()))
		}
		return nil, nil
	}
	var (
		showMsg *protocol.ShowMessageParams
		wg      sync.WaitGroup
	)
	for _, ph := range wsPackages {
		wg.Add(1)
		go func(ph source.PackageHandle) {
			defer wg.Done()

			// Only run analyses for packages with open files.
			withAnalysis := alwaysAnalyze
			for _, pgh := range ph.CompiledGoFiles() {
				if snapshot.IsOpen(pgh.File().URI()) {
					withAnalysis = true
					break
				}
			}

			pkgReports, warn, err := source.Diagnostics(ctx, snapshot, ph, withAnalysis)

			// Check if might want to warn the user about their build configuration.
			// Our caller decides whether to send the message.
			if warn && !snapshot.View().ValidBuildConfiguration() {
				showMsg = &protocol.ShowMessageParams{
					Type:    protocol.Warning,
					Message: `You are neither in a module nor in your GOPATH. If you are using modules, please open your editor to a directory in your module. If you believe this warning is incorrect, please file an issue: https://github.com/golang/go/issues/new.`,
				}
			}
			if err != nil {
				event.Error(ctx, "warning: diagnose package", err, tag.Snapshot.Of(snapshot.ID()), tag.Package.Of(ph.ID()))
				return
			}

			// Add all reports to the global map, checking for duplciates.
			reportsMu.Lock()
			for id, diags := range pkgReports {
				key := idWithAnalysis{
					id:           id,
					withAnalysis: withAnalysis,
				}
				if _, ok := reports[key]; !ok {
					reports[key] = map[string]*source.Diagnostic{}
				}
				for _, d := range diags {
					reports[key][diagnosticKey(d)] = d
				}
			}
			reportsMu.Unlock()
		}(ph)
	}
	wg.Wait()
	return reports, showMsg
}

// diagnosticKey creates a unique identifier for a given diagnostic, since we
// cannot use source.Diagnostics as map keys. This is used to de-duplicate
// diagnostics.
func diagnosticKey(d *source.Diagnostic) string {
	var tags, related string
	for _, t := range d.Tags {
		tags += fmt.Sprintf("%s", t)
	}
	for _, r := range d.Related {
		related += fmt.Sprintf("%s%s%s", r.URI, r.Message, r.Range)
	}
	key := fmt.Sprintf("%s%s%s%s%s%s", d.Message, d.Range, d.Severity, d.Source, tags, related)
	return fmt.Sprintf("%x", sha1.Sum([]byte(key)))
}

func (s *Server) publishReports(ctx context.Context, snapshot source.Snapshot, reports map[idWithAnalysis]map[string]*source.Diagnostic) {
	// Check for context cancellation before publishing diagnostics.
	if ctx.Err() != nil {
		return
	}

	s.deliveredMu.Lock()
	defer s.deliveredMu.Unlock()

	for key, diagnosticsMap := range reports {
		// Don't deliver diagnostics if the context has already been canceled.
		if ctx.Err() != nil {
			break
		}
		// Pre-sort diagnostics to avoid extra work when we compare them.
		var diagnostics []*source.Diagnostic
		for _, d := range diagnosticsMap {
			diagnostics = append(diagnostics, d)
		}
		source.SortDiagnostics(diagnostics)
		toSend := sentDiagnostics{
			version:      key.id.Version,
			identifier:   key.id.Identifier,
			sorted:       diagnostics,
			withAnalysis: key.withAnalysis,
			snapshotID:   snapshot.ID(),
		}

		// We use the zero values if this is an unknown file.
		delivered := s.delivered[key.id.URI]

		// Snapshot IDs are always increasing, so we use them instead of file
		// versions to create the correct order for diagnostics.

		// If we've already delivered diagnostics for a future snapshot for this file,
		// do not deliver them.
		if delivered.snapshotID > toSend.snapshotID {
			// Do not update the delivered map since it already contains newer diagnostics.
			continue
		}

		// Check if we should reuse the cached diagnostics.
		if equalDiagnostics(delivered.sorted, diagnostics) {
			// Make sure to update the delivered map.
			s.delivered[key.id.URI] = toSend
			continue
		}

		// If we've already delivered diagnostics for this file, at this
		// snapshot, with analyses, do not send diagnostics without analyses.
		if delivered.snapshotID == toSend.snapshotID && delivered.version == toSend.version &&
			delivered.withAnalysis && !toSend.withAnalysis {
			// Do not update the delivered map since it already contains better diagnostics.
			continue
		}
		if err := s.client.PublishDiagnostics(ctx, &protocol.PublishDiagnosticsParams{
			Diagnostics: toProtocolDiagnostics(diagnostics),
			URI:         protocol.URIFromSpanURI(key.id.URI),
			Version:     key.id.Version,
		}); err != nil {
			event.Error(ctx, "publishReports: failed to deliver diagnostic", err, tag.URI.Of(key.id.URI))
			continue
		}
		// Update the delivered map.
		s.delivered[key.id.URI] = toSend
	}
}

// equalDiagnostics returns true if the 2 lists of diagnostics are equal.
// It assumes that both a and b are already sorted.
func equalDiagnostics(a, b []*source.Diagnostic) bool {
	if len(a) != len(b) {
		return false
	}
	for i := 0; i < len(a); i++ {
		if source.CompareDiagnostic(a[i], b[i]) != 0 {
			return false
		}
	}
	return true
}

func toProtocolDiagnostics(diagnostics []*source.Diagnostic) []protocol.Diagnostic {
	reports := []protocol.Diagnostic{}
	for _, diag := range diagnostics {
		related := make([]protocol.DiagnosticRelatedInformation, 0, len(diag.Related))
		for _, rel := range diag.Related {
			related = append(related, protocol.DiagnosticRelatedInformation{
				Location: protocol.Location{
					URI:   protocol.URIFromSpanURI(rel.URI),
					Range: rel.Range,
				},
				Message: rel.Message,
			})
		}
		reports = append(reports, protocol.Diagnostic{
			Message:            strings.TrimSpace(diag.Message), // go list returns errors prefixed by newline
			Range:              diag.Range,
			Severity:           diag.Severity,
			Source:             diag.Source,
			Tags:               diag.Tags,
			RelatedInformation: related,
		})
	}
	return reports
}

func (s *Server) handleFatalErrors(ctx context.Context, snapshot source.Snapshot, modErr, loadErr error) bool {
	modURI := snapshot.View().ModFile()

	// We currently only have workarounds for errors associated with modules.
	if modURI == "" {
		return false
	}

	switch loadErr {
	case source.InconsistentVendoring:
		item, err := s.client.ShowMessageRequest(ctx, &protocol.ShowMessageRequestParams{
			Type: protocol.Error,
			Message: `Inconsistent vendoring detected. Please re-run "go mod vendor".
See https://github.com/golang/go/issues/39164 for more detail on this issue.`,
			Actions: []protocol.MessageActionItem{
				{Title: "go mod vendor"},
			},
		})
		// If the user closes the pop-up, don't show them further errors.
		if item == nil {
			return true
		}
		if err != nil {
			event.Error(ctx, "go mod vendor ShowMessageRequest failed", err, tag.Directory.Of(snapshot.View().Folder().Filename()))
			return true
		}
		if err := s.directGoModCommand(ctx, protocol.URIFromSpanURI(modURI), "mod", []string{"vendor"}...); err != nil {
			if err := s.client.ShowMessage(ctx, &protocol.ShowMessageParams{
				Type:    protocol.Error,
				Message: fmt.Sprintf(`"go mod vendor" failed with %v`, err),
			}); err != nil {
				if err != nil {
					event.Error(ctx, "go mod vendor ShowMessage failed", err, tag.Directory.Of(snapshot.View().Folder().Filename()))
				}
			}
		}
		return true
	}
	// If there is a go.mod-related error, as well as a workspace load error,
	// there is likely an issue with the go.mod file. Try to parse the error
	// message and create a diagnostic.
	if modErr == nil {
		return false
	}
	if xerrors.Is(loadErr, source.PackagesLoadError) {
		fh, err := snapshot.GetFile(ctx, modURI)
		if err != nil {
			return false
		}
		diag, err := mod.ExtractGoCommandError(ctx, snapshot, fh, loadErr)
		if err != nil {
			return false
		}
		s.publishReports(ctx, snapshot, map[idWithAnalysis]map[string]*source.Diagnostic{
			{id: fh.Identity()}: {diagnosticKey(diag): diag},
		})
		return true
	}
	return false
}