package artifacts

import (
	"encoding/json"
	"os"
	"path/filepath"
	"strings"

	"gitea.maximumdirect.net/eric/narratio/internal/fileops"
	"gitea.maximumdirect.net/eric/narratio/internal/manifest"
)

type ExtractionEvidenceState string

const (
	ExtractionEvidenceValid    ExtractionEvidenceState = "valid"
	ExtractionEvidenceAbsent   ExtractionEvidenceState = "absent"
	ExtractionEvidenceObsolete ExtractionEvidenceState = "obsolete"
	ExtractionEvidenceUnsafe   ExtractionEvidenceState = "unsafe"
)

// ExtractionEvidence is a policy-neutral proof of configured extraction output.
type ExtractionEvidence struct {
	State                 ExtractionEvidenceState
	Reason, ProducerRunID string
	Outputs               map[string]string
}

// InspectExtractionEvidence verifies structure, confinement, identities, contracts, and payload bytes.
func InspectExtractionEvidence(
	paths SessionPaths,
	m *manifest.Manifest,
	configured map[string]ExtractionArtifactDefinition,
	input ExtractionInputIdentity,
) ExtractionEvidence {
	if m == nil || len(configured) == 0 {
		return ExtractionEvidence{State: ExtractionEvidenceAbsent, Reason: "extraction evidence is absent"}
	}
	r := m.Stages[extractStageName]
	if r == nil || r.Name != extractStageName || r.Status != manifest.StatusSucceeded {
		return ExtractionEvidence{State: ExtractionEvidenceAbsent, Reason: "extract stage has no succeeded result"}
	}
	if !extractionInputMatchesMetadata(r.Metadata, input) {
		return ExtractionEvidence{State: ExtractionEvidenceObsolete, Reason: "extract result does not match the current trimmed transcript"}
	}
	runID := extractionMetadataString(r.Metadata, extractionMetadataRun)
	if !safeExtractionPathSegment(runID) {
		return ExtractionEvidence{State: ExtractionEvidenceObsolete, Reason: "extract result has an invalid producing run ID"}
	}
	root := filepath.Clean(filepath.Join(paths.ArtifactsDir, "notarius", runID))
	if !filepath.IsAbs(root) || extractionMetadataString(r.Metadata, extractionMetadataRoot) != root {
		return ExtractionEvidence{State: ExtractionEvidenceObsolete, Reason: "extract result does not identify its canonical immutable bundle"}
	}
	info, err := os.Lstat(root)
	if os.IsNotExist(err) {
		return ExtractionEvidence{State: ExtractionEvidenceObsolete, Reason: "immutable Notarius bundle is missing"}
	}
	if err != nil || info.Mode()&os.ModeSymlink != 0 {
		return ExtractionEvidence{State: ExtractionEvidenceUnsafe, Reason: "immutable Notarius bundle is unsafe"}
	}
	if !info.IsDir() {
		return ExtractionEvidence{State: ExtractionEvidenceObsolete, Reason: "immutable Notarius bundle is not a directory"}
	}
	if !safeExistingExtractionDirectory(paths.Root, root) {
		return ExtractionEvidence{State: ExtractionEvidenceUnsafe, Reason: "immutable Notarius bundle is unsafe"}
	}
	receiptRunID, receiptPipelineID := extractionReceiptIdentity(r.Metadata)
	if receiptRunID == "" || receiptPipelineID == "" {
		return ExtractionEvidence{State: ExtractionEvidenceObsolete, Reason: "extract result has incompatible Notarius receipt identity"}
	}
	expected := make(map[string]ExtractionArtifactDefinition, len(configured))
	for key, d := range configured {
		expected[ExtractionArtifactSourceID(key)] = d
	}
	seen, outputs := map[string]struct{}{}, map[string]string{}
	indexSeen := false
	for _, out := range r.Outputs {
		if strings.TrimSpace(out.ProducerRunID) != runID {
			return ExtractionEvidence{State: ExtractionEvidenceObsolete, Reason: "extract output producer identity is inconsistent"}
		}
		if out.SourceID == "" {
			if indexSeen || out.Kind != extractionIndexKind || filepath.Clean(out.LocalPath) != filepath.Join(root, "index.json") {
				return ExtractionEvidence{State: ExtractionEvidenceObsolete, Reason: "extract index path is not canonical"}
			}
			if state, reason := inspectExtractionPayload(root, out.LocalPath, out.Checksum); state != ExtractionEvidenceValid {
				return ExtractionEvidence{State: state, Reason: reason}
			}
			indexSeen = true
			continue
		}
		d, ok := expected[out.SourceID]
		if !ok || out.Kind != extractionLaneKind {
			return ExtractionEvidence{State: ExtractionEvidenceObsolete, Reason: "extract result source set differs from current configuration"}
		}
		if _, duplicate := seen[out.SourceID]; duplicate {
			return ExtractionEvidence{State: ExtractionEvidenceObsolete, Reason: "extract result contains a duplicate configured source"}
		}
		if !compatibleCatalogExtractionContract(out.Contract, d) || !compatibleCatalogExtractionProvenance(out.ExternalProvenance, receiptRunID, receiptPipelineID, d) {
			return ExtractionEvidence{State: ExtractionEvidenceObsolete, Reason: "extract output contract or provenance is incompatible"}
		}
		if state, reason := inspectExtractionPayload(root, out.LocalPath, out.Checksum); state != ExtractionEvidenceValid {
			return ExtractionEvidence{State: state, Reason: reason}
		}
		seen[out.SourceID] = struct{}{}
		outputs[out.SourceID] = out.LocalPath
	}
	if !indexSeen || len(seen) != len(expected) || len(r.Outputs) != len(expected)+1 {
		return ExtractionEvidence{State: ExtractionEvidenceObsolete, Reason: "extract result is incomplete"}
	}
	return ExtractionEvidence{State: ExtractionEvidenceValid, ProducerRunID: runID, Outputs: outputs}
}

func inspectExtractionPayload(root, path, checksum string) (ExtractionEvidenceState, string) {
	if !filepath.IsAbs(path) || !pathWithinExtractionRoot(root, path) || strings.TrimSpace(checksum) == "" {
		return ExtractionEvidenceUnsafe, "extract output path or checksum is unsafe"
	}
	info, err := os.Lstat(path)
	if os.IsNotExist(err) {
		return ExtractionEvidenceObsolete, "extract output is missing"
	}
	if !safeExtractionComponents(root, path) {
		return ExtractionEvidenceUnsafe, "extract output path contains unsafe components"
	}
	if err != nil || !info.Mode().IsRegular() || info.Mode()&os.ModeSymlink != 0 {
		return ExtractionEvidenceUnsafe, "extract output is not a regular file"
	}
	actual, err := SHA256File(path)
	if err != nil {
		return ExtractionEvidenceUnsafe, "extract output checksum cannot be read"
	}
	if actual != checksum {
		return ExtractionEvidenceObsolete, "extract output checksum does not match durable bytes"
	}
	body, err := fileops.ReadRegularFile(path, MaxExtractionPayloadBytes)
	if err != nil || !json.Valid(body) {
		return ExtractionEvidenceObsolete, "extract output is not valid JSON"
	}
	return ExtractionEvidenceValid, ""
}