package json

import (
	"context"
	stdjson "encoding/json"
	"fmt"
	"regexp"
	"sort"
	"strings"

	"gitea.maximumdirect.net/eric/notarius/internal/core/artifacts"
	"gitea.maximumdirect.net/eric/notarius/internal/core/source"
	"gitea.maximumdirect.net/eric/notarius/internal/framework/contracts"
	"gitea.maximumdirect.net/eric/notarius/internal/framework/pipeline"
)

const Key = "json"

const contentTypeJSON = "application/json"

var safeArtifactFileChar = regexp.MustCompile(`[^A-Za-z0-9._-]`)

var _ contracts.OutputEncoder = (*Encoder)(nil)

type Encoder struct{}

func New() *Encoder {
	return &Encoder{}
}

func (e *Encoder) Key() string {
	return Key
}

func (e *Encoder) Encode(ctx context.Context, req contracts.OutputRequest) (contracts.OutputResult, error) {
	if e == nil {
		return contracts.OutputResult{}, encoderErrorf("encoder must not be nil")
	}
	if ctx == nil {
		return contracts.OutputResult{}, encoderErrorf("context must not be nil")
	}
	if err := ctx.Err(); err != nil {
		return contracts.OutputResult{}, encoderErrorf("context error before encoding: %w", err)
	}

	files, err := logicalFiles(req)
	if err != nil {
		return contracts.OutputResult{}, err
	}
	return contracts.OutputResult{Files: files}, nil
}

func ModuleSpec() pipeline.ModuleSpec {
	return pipeline.ModuleSpec{
		Key:      Key,
		Stage:    pipeline.StageOutput,
		Requires: []string{"normalized"},
		Provides: []string{"encoded"},
	}
}

func Register(registry *pipeline.OutputEncoderRegistry) error {
	return registry.RegisterWithSpec(ModuleSpec(), func() (contracts.OutputEncoder, error) {
		return New(), nil
	})
}

type indexFile struct {
	ManifestFile  string              `json:"manifest_file"`
	ArtifactFiles []artifactFileIndex `json:"artifact_files"`
	RejectedFile  string              `json:"rejected_file"`
	WarningsFile  string              `json:"warnings_file"`
}

type artifactFileIndex struct {
	ArtifactType string `json:"artifact_type"`
	File         string `json:"file"`
}

type artifactFile struct {
	ArtifactType string               `json:"artifact_type"`
	Artifacts    []artifacts.Artifact `json:"artifacts"`
}

type rejectedFile struct {
	Rejected []artifacts.RejectedArtifact `json:"rejected"`
}

type warningsFile struct {
	Warnings []contracts.Warning `json:"warnings"`
}

func logicalFiles(req contracts.OutputRequest) ([]contracts.OutputFile, error) {
	artifactsByType := make(map[string][]artifacts.Artifact)
	for _, artifact := range req.Approved {
		artifactsByType[artifact.ArtifactType] = append(artifactsByType[artifact.ArtifactType], cloneArtifact(artifact))
	}

	artifactTypes := make([]string, 0, len(artifactsByType))
	for artifactType := range artifactsByType {
		artifactTypes = append(artifactTypes, artifactType)
	}
	sort.Strings(artifactTypes)

	artifactIndexes := make([]artifactFileIndex, 0, len(artifactTypes))
	files := make([]contracts.OutputFile, 0, len(artifactTypes)+4)
	manifestFile, err := jsonFile("manifest.json", req.Manifest)
	if err != nil {
		return nil, err
	}
	files = append(files, manifestFile)

	usedArtifactFiles := make(map[string]string, len(artifactTypes))
	for _, artifactType := range artifactTypes {
		name, err := artifactFileName(artifactType)
		if err != nil {
			return nil, err
		}
		if existingType, ok := usedArtifactFiles[name]; ok {
			return nil, encoderErrorf("artifact types %q and %q produce duplicate output file %q", existingType, artifactType, name)
		}
		usedArtifactFiles[name] = artifactType
		artifactIndexes = append(artifactIndexes, artifactFileIndex{
			ArtifactType: artifactType,
			File:         name,
		})
		file, err := jsonFile(name, artifactFile{
			ArtifactType: artifactType,
			Artifacts:    artifactsByType[artifactType],
		})
		if err != nil {
			return nil, err
		}
		files = append(files, file)
	}

	index := indexFile{
		ManifestFile:  "manifest.json",
		ArtifactFiles: artifactIndexes,
		RejectedFile:  "rejected.json",
		WarningsFile:  "warnings.json",
	}
	indexOutput, err := jsonFile("index.json", index)
	if err != nil {
		return nil, err
	}
	rejectedOutput, err := jsonFile("rejected.json", rejectedFile{Rejected: cloneRejected(req.Rejected)})
	if err != nil {
		return nil, err
	}
	warningsOutput, err := jsonFile("warnings.json", warningsFile{Warnings: cloneWarnings(req.Warnings)})
	if err != nil {
		return nil, err
	}
	files = append(files, indexOutput, rejectedOutput, warningsOutput)
	sort.Slice(files, func(i, j int) bool {
		return files[i].Name < files[j].Name
	})
	return files, nil
}

func jsonFile(name string, value any) (contracts.OutputFile, error) {
	data, err := marshalPretty(value)
	if err != nil {
		return contracts.OutputFile{}, encoderErrorf("encode %s: %w", name, err)
	}
	return contracts.OutputFile{
		Name:        name,
		ContentType: contentTypeJSON,
		Bytes:       data,
	}, nil
}

func marshalPretty(value any) ([]byte, error) {
	data, err := stdjson.MarshalIndent(value, "", "  ")
	if err != nil {
		return nil, err
	}
	return append(data, '\n'), nil
}

func artifactFileName(artifactType string) (string, error) {
	sanitized := safeArtifactFileChar.ReplaceAllString(strings.TrimSpace(artifactType), "_")
	for strings.Contains(sanitized, "..") {
		sanitized = strings.ReplaceAll(sanitized, "..", "__")
	}
	sanitized = strings.Trim(sanitized, "._")
	if sanitized == "" {
		return "", encoderErrorf("artifact type %q cannot produce a safe file name", artifactType)
	}
	return "artifacts/" + sanitized + ".json", nil
}

func cloneArtifact(artifact artifacts.Artifact) artifacts.Artifact {
	return artifacts.Artifact{
		ExtractorKey:  artifact.ExtractorKey,
		ArtifactType:  artifact.ArtifactType,
		SchemaVersion: artifact.SchemaVersion,
		Payload:       append(stdjson.RawMessage(nil), artifact.Payload...),
		SourceRefs:    append([]source.SourceRef(nil), artifact.SourceRefs...),
		Metadata:      cloneMetadata(artifact.Metadata),
	}
}

func cloneRejected(rejected []artifacts.RejectedArtifact) []artifacts.RejectedArtifact {
	if len(rejected) == 0 {
		return []artifacts.RejectedArtifact{}
	}
	out := make([]artifacts.RejectedArtifact, 0, len(rejected))
	for _, item := range rejected {
		out = append(out, artifacts.RejectedArtifact{
			Candidate:     cloneCandidate(item.Candidate),
			ValidatorName: item.ValidatorName,
			ReasonCode:    item.ReasonCode,
			Message:       item.Message,
		})
	}
	return out
}

func cloneCandidate(candidate artifacts.ArtifactCandidate) artifacts.ArtifactCandidate {
	return artifacts.ArtifactCandidate{
		Index:         candidate.Index,
		ExtractorKey:  candidate.ExtractorKey,
		ArtifactType:  candidate.ArtifactType,
		SchemaVersion: candidate.SchemaVersion,
		Payload:       append(stdjson.RawMessage(nil), candidate.Payload...),
		SourceRefs:    append([]source.SourceRef(nil), candidate.SourceRefs...),
		Metadata:      cloneMetadata(candidate.Metadata),
	}
}

func cloneWarnings(warnings []contracts.Warning) []contracts.Warning {
	if len(warnings) == 0 {
		return []contracts.Warning{}
	}
	return append([]contracts.Warning(nil), warnings...)
}

func cloneMetadata(metadata map[string]any) map[string]any {
	if len(metadata) == 0 {
		return nil
	}
	out := make(map[string]any, len(metadata))
	for key, value := range metadata {
		out[key] = value
	}
	return out
}

func encoderErrorf(format string, args ...any) error {
	return fmt.Errorf("json output encoder: "+format, args...)
}