// 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/telemetry/log"
	"golang.org/x/tools/internal/telemetry/trace"
)

func (s *Server) diagnose(snapshot source.Snapshot, fh source.FileHandle) error {
	switch fh.Identity().Kind {
	case source.Go:
		go s.diagnoseFile(snapshot, fh)
	case source.Mod:
		go s.diagnoseSnapshot(snapshot)
	}
	return nil
}

func (s *Server) diagnoseSnapshot(snapshot source.Snapshot) {
	ctx := snapshot.View().BackgroundContext()
	ctx, done := trace.StartSpan(ctx, "lsp:background-worker")
	defer done()

	for _, id := range snapshot.WorkspacePackageIDs(ctx) {
		ph, err := snapshot.PackageHandle(ctx, id)
		if err != nil {
			log.Error(ctx, "diagnoseSnapshot: no PackageHandle for workspace package", err, telemetry.Package.Of(id))
			continue
		}
		if len(ph.CompiledGoFiles()) == 0 {
			continue
		}
		// Find a file on which to call diagnostics.
		uri := ph.CompiledGoFiles()[0].File().Identity().URI
		fh, err := snapshot.GetFile(ctx, uri)
		if err != nil {
			continue
		}
		// Run diagnostics on the workspace package.
		go func(snapshot source.Snapshot, fh source.FileHandle) {
			reports, _, err := source.Diagnostics(ctx, snapshot, fh, false, snapshot.View().Options().DisabledAnalyses)
			if err != nil {
				log.Error(ctx, "no diagnostics", err, telemetry.URI.Of(fh.Identity().URI))
				return
			}
			// Don't publish empty diagnostics.
			s.publishReports(ctx, reports, false)
		}(snapshot, fh)
	}
}

func (s *Server) diagnoseFile(snapshot source.Snapshot, fh source.FileHandle) {
	ctx := snapshot.View().BackgroundContext()
	ctx, done := trace.StartSpan(ctx, "lsp:background-worker")
	defer done()

	ctx = telemetry.File.With(ctx, fh.Identity().URI)

	reports, warningMsg, err := source.Diagnostics(ctx, snapshot, fh, true, snapshot.View().Options().DisabledAnalyses)
	// Check the warning message first.
	if warningMsg != "" {
		s.client.ShowMessage(ctx, &protocol.ShowMessageParams{
			Type:    protocol.Info,
			Message: warningMsg,
		})
	}
	if err != nil {
		if err != context.Canceled {
			log.Error(ctx, "diagnoseFile: could not generate diagnostics", err)
		}
		return
	}
	// Publish empty diagnostics for files.
	s.publishReports(ctx, reports, true)
}

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

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

	for fileID, diagnostics := range reports {
		// Don't deliver diagnostics if the context has already been canceled.
		if ctx.Err() != nil {
			break
		}
		// Don't publish empty diagnostics unless specified.
		if len(diagnostics) == 0 && !publishEmpty {
			continue
		}
		// Pre-sort diagnostics to avoid extra work when we compare them.
		source.SortDiagnostics(diagnostics)
		toSend := sentDiagnostics{
			version:    fileID.Version,
			identifier: fileID.Identifier,
			sorted:     diagnostics,
		}

		if delivered, ok := s.delivered[fileID.URI]; ok {
			// We only reuse cached diagnostics in two cases:
			//   1. This file is at a greater version than that of the previously sent diagnostics.
			//   2. There are no known versions for the file.
			greaterVersion := fileID.Version > delivered.version && delivered.version > 0
			noVersions := (fileID.Version == 0 && delivered.version == 0) && delivered.identifier == fileID.Identifier
			if (greaterVersion || noVersions) && equalDiagnostics(delivered.sorted, diagnostics) {
				// Update the delivered map even if we reuse cached diagnostics.
				s.delivered[fileID.URI] = toSend
				continue
			}
		}
		if err := s.client.PublishDiagnostics(ctx, &protocol.PublishDiagnosticsParams{
			Diagnostics: toProtocolDiagnostics(ctx, diagnostics),
			URI:         protocol.NewURI(fileID.URI),
			Version:     fileID.Version,
		}); err != nil {
			log.Error(ctx, "failed to deliver diagnostic", err, telemetry.File)
			continue
		}
		// Update the delivered map.
		s.delivered[fileID.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(ctx context.Context, 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.NewURI(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
}