package distillation

// scorer.go — pure deterministic Success Scorer (port of Rust
// scripts/distillation/scorer.ts at e7636f2).
//
// Takes one EvidenceRecord, returns category + reasons + sub_scores.
// NO I/O, NO LLM, NO clock reads, NO mutable state. Identical input
// → identical output forever. Same contract as the Rust source —
// future scoring-rule changes bump ScorerVersion atomically with
// the logic.
//
// Three-class strategy mirrors the Rust source taxonomy
// (docs/recon/local-distillation-recon.md + data/_kb/evidence_health.md):
//
//   CLASS A — verdict-bearing
//     scrum_reviews, observer_reviews, audits, contract_analyses
//     Direct scoring from existing markers / observer_verdict
//
//   CLASS B — telemetry-rich
//     auto_apply, outcomes, mode_experiments
//     Markers exist but partial; needs_human_review fills the gap
//
//   CLASS C — pure-extraction (no native scoring signal)
//     distilled_*, audit_facts, observer_escalations
//     Default needs_human_review; v2 will JOIN to parent verdict

import (
	"crypto/sha256"
	"encoding/hex"
	"encoding/json"
	"fmt"
	"strconv"
	"strings"
)

// sourceClass categorizes an EvidenceRecord's source_file for the
// scorer's three-class dispatch.
type sourceClass string

const (
	classVerdict    sourceClass = "verdict"
	classTelemetry  sourceClass = "telemetry"
	classExtraction sourceClass = "extraction"
)

// sourceClassFor maps a source_file (from provenance) to a class.
// Centralized so adding a new source is a one-line change. Mirrors
// the Rust switch on the stem (data/_kb/X.jsonl → X).
func sourceClassFor(sourceFile string) sourceClass {
	stem := strings.TrimSuffix(strings.TrimPrefix(sourceFile, "data/_kb/"), ".jsonl")
	switch stem {
	case "scrum_reviews", "observer_reviews", "audits", "contract_analyses":
		return classVerdict
	case "auto_apply", "outcomes", "mode_experiments":
		return classTelemetry
	case "distilled_facts", "distilled_procedures", "distilled_config_hints",
		"audit_facts", "observer_escalations":
		return classExtraction
	default:
		// Unknown source → most conservative path (forces
		// needs_human_review until a transform is added).
		return classExtraction
	}
}

// stemOf extracts the stable corpus identifier from a source_file.
// E.g. "data/_kb/scrum_reviews.jsonl" → "scrum_reviews".
func stemOf(sourceFile string) string {
	return strings.TrimSuffix(strings.TrimPrefix(sourceFile, "data/_kb/"), ".jsonl")
}

// ScoreOutput is the scorer's return shape — category + reasons +
// the captured sub-signals. Reasons is always non-empty (validator
// requires it).
type ScoreOutput struct {
	Category  ScoreCategory
	Reasons   []string
	SubScores *SubScores
}

// ScoreRecord dispatches an EvidenceRecord to the appropriate class
// scorer and returns the verdict + reasons + sub-scores. Pure
// function. Caller wraps the output in a ScoredRun via BuildScoredRun
// for the on-wire shape.
func ScoreRecord(rec EvidenceRecord) ScoreOutput {
	cls := sourceClassFor(rec.Provenance.SourceFile)
	stem := stemOf(rec.Provenance.SourceFile)

	switch cls {
	case classVerdict:
		switch stem {
		case "scrum_reviews":
			return scoreScrumReview(rec)
		case "observer_reviews":
			return scoreObserverReview(rec)
		case "audits":
			return scoreAudit(rec)
		case "contract_analyses":
			return scoreContractAnalysis(rec)
		}
	case classTelemetry:
		switch stem {
		case "auto_apply":
			return scoreAutoApply(rec)
		case "outcomes":
			return scoreOutcomes(rec)
		case "mode_experiments":
			return scoreModeExperiment(rec)
		}
	}
	return scoreExtraction()
}

// BuildScoredRun composes a complete ScoredRun for persistence.
// Caller supplies recorded_at + the source file path/line offset.
// SigHash is computed deterministically from the EvidenceRecord
// JSON; ScoredRun traces to the materialized evidence row.
func BuildScoredRun(rec EvidenceRecord, sourceFile string, lineOffset int64, recordedAt string) (ScoredRun, error) {
	out := ScoreRecord(rec)
	sig, err := canonicalSha256(rec)
	if err != nil {
		return ScoredRun{}, fmt.Errorf("scoredrun sig hash: %w", err)
	}
	return ScoredRun{
		SchemaVersion:  ScoredRunSchemaVersion,
		EvidenceRunID:  rec.RunID,
		EvidenceTaskID: rec.TaskID,
		Category:       out.Category,
		Reasons:        out.Reasons,
		ScoredAt:       recordedAt,
		ScorerVersion:  ScorerVersion,
		SubScores:      out.SubScores,
		Provenance: Provenance{
			SourceFile: sourceFile,
			LineOffset: lineOffset,
			SigHash:    sig,
			RecordedAt: recordedAt,
		},
	}, nil
}

// canonicalSha256 hashes a value's canonical JSON encoding. Used
// for ScoredRun.Provenance.SigHash. Matches the Rust pattern of
// "hash the structured object, not the raw source bytes" so
// re-materialization with same logic produces same hash.
func canonicalSha256(v any) (string, error) {
	bs, err := json.Marshal(v)
	if err != nil {
		return "", err
	}
	sum := sha256.Sum256(bs)
	return hex.EncodeToString(sum[:]), nil
}

// ─── Class A: verdict-bearing ────────────────────────────────────

func scoreScrumReview(r EvidenceRecord) ScoreOutput {
	subs := &SubScores{}
	successMarker := findPrefix(r.SuccessMarkers, "accepted_on_attempt_")
	if successMarker == "" {
		return ScoreOutput{
			Category: CategoryNeedsHumanReview,
			Reasons:  []string{"scrum_review missing accepted_on_attempt_* success marker"},
			SubScores: subs,
		}
	}
	attemptStr := strings.TrimPrefix(successMarker, "accepted_on_attempt_")
	attempt, err := strconv.Atoi(attemptStr)
	if err != nil {
		return ScoreOutput{
			Category: CategoryNeedsHumanReview,
			Reasons:  []string{"scrum_review accepted_on_attempt_* marker has non-integer suffix: " + attemptStr},
			SubScores: subs,
		}
	}
	subs.AcceptedOnAttempt = &attempt
	switch {
	case attempt == 1:
		return ScoreOutput{
			Category: CategoryAccepted,
			Reasons:  []string{"scrum: accepted on first attempt"},
			SubScores: subs,
		}
	case attempt <= 3:
		return ScoreOutput{
			Category: CategoryPartiallyAccepted,
			Reasons:  []string{fmt.Sprintf("scrum: accepted after %d attempts", attempt)},
			SubScores: subs,
		}
	default:
		return ScoreOutput{
			Category: CategoryPartiallyAccepted,
			Reasons:  []string{fmt.Sprintf("scrum: accepted only after %d attempts (high-cost path)", attempt)},
			SubScores: subs,
		}
	}
}

func scoreObserverReview(r EvidenceRecord) ScoreOutput {
	subs := &SubScores{}
	switch r.ObserverVerdict {
	case VerdictAccept:
		subs.ObserverVerdict = VerdictAccept
		return ScoreOutput{
			Category: CategoryAccepted,
			Reasons:  []string{"observer accepted the reviewed attempt"},
			SubScores: subs,
		}
	case VerdictReject:
		subs.ObserverVerdict = VerdictReject
		return ScoreOutput{
			Category: CategoryRejected,
			Reasons:  []string{"observer rejected the reviewed attempt"},
			SubScores: subs,
		}
	case VerdictCycle:
		subs.ObserverVerdict = VerdictCycle
		return ScoreOutput{
			Category: CategoryPartiallyAccepted,
			Reasons:  []string{"observer flagged the attempt as cycling — partial signal"},
			SubScores: subs,
		}
	default:
		return ScoreOutput{
			Category: CategoryNeedsHumanReview,
			Reasons:  []string{fmt.Sprintf("observer_verdict missing or unrecognized: %q", r.ObserverVerdict)},
			SubScores: subs,
		}
	}
}

func scoreAudit(r EvidenceRecord) ScoreOutput {
	subs := &SubScores{}
	succ := r.SuccessMarkers
	fail := r.FailureMarkers

	// Legacy markers (back-compat with pre-fix materializations).
	if contains(succ, "approved") {
		return ScoreOutput{Category: CategoryAccepted,
			Reasons: []string{"audit overall=approved (legacy marker)"}, SubScores: subs}
	}
	if contains(fail, "blocked") {
		return ScoreOutput{Category: CategoryRejected,
			Reasons: []string{"audit overall=block (legacy marker)"}, SubScores: subs}
	}
	if contains(fail, "request_changes") {
		return ScoreOutput{Category: CategoryPartiallyAccepted,
			Reasons: []string{"audit overall=request_changes (legacy marker)"}, SubScores: subs}
	}

	// Severity-derived markers (Phase 2 transform).
	sevSucc := findPrefix(succ, "audit_severity_")
	sevFail := findPrefix(fail, "audit_severity_")
	if sevSucc != "" {
		return ScoreOutput{Category: CategoryAccepted,
			Reasons: []string{sevSucc + " → minor finding"}, SubScores: subs}
	}
	if sevFail == "audit_severity_medium" {
		return ScoreOutput{Category: CategoryPartiallyAccepted,
			Reasons: []string{"audit_severity_medium → finding warrants review"}, SubScores: subs}
	}
	if sevFail == "audit_severity_high" || sevFail == "audit_severity_critical" {
		return ScoreOutput{Category: CategoryRejected,
			Reasons: []string{sevFail + " → blocking finding"}, SubScores: subs}
	}
	return ScoreOutput{Category: CategoryNeedsHumanReview,
		Reasons: []string{"audit row has no severity or overall marker"}, SubScores: subs}
}

func scoreContractAnalysis(r EvidenceRecord) ScoreOutput {
	subs := &SubScores{}
	// failure_markers takes precedence: explicit rejection beats absent verdict.
	if contains(r.FailureMarkers, "observer_rejected") || r.ObserverVerdict == VerdictReject {
		subs.ObserverVerdict = VerdictReject
		return ScoreOutput{Category: CategoryRejected,
			Reasons: []string{"contract analysis: observer rejected"}, SubScores: subs}
	}
	switch r.ObserverVerdict {
	case VerdictAccept:
		subs.ObserverVerdict = VerdictAccept
		return ScoreOutput{Category: CategoryAccepted,
			Reasons: []string{"contract analysis: observer accepted"}, SubScores: subs}
	case VerdictCycle:
		subs.ObserverVerdict = VerdictCycle
		return ScoreOutput{Category: CategoryPartiallyAccepted,
			Reasons: []string{"contract analysis: observer cycled (partial)"}, SubScores: subs}
	}
	return ScoreOutput{Category: CategoryNeedsHumanReview,
		Reasons: []string{"contract analysis: no observer verdict signal"}, SubScores: subs}
}

// ─── Class B: telemetry-rich ─────────────────────────────────────

func scoreAutoApply(r EvidenceRecord) ScoreOutput {
	subs := &SubScores{}
	if contains(r.SuccessMarkers, "committed") {
		t := true
		subs.CargoGreen = &t
		return ScoreOutput{Category: CategoryAccepted,
			Reasons: []string{"auto_apply: patch committed (cargo green + warning baseline + rationale alignment passed)"},
			SubScores: subs}
	}
	reverted := findContaining(r.FailureMarkers, "reverted")
	if reverted != "" {
		if strings.Contains(reverted, "build_red") {
			f := false
			subs.CargoGreen = &f
		}
		return ScoreOutput{Category: CategoryRejected,
			Reasons: []string{"auto_apply: " + reverted}, SubScores: subs}
	}
	return ScoreOutput{Category: CategoryNeedsHumanReview,
		Reasons: []string{"auto_apply: no commit + no revert (likely no_patches or dry_run)"},
		SubScores: subs}
}

func scoreOutcomes(r EvidenceRecord) ScoreOutput {
	subs := &SubScores{}
	if contains(r.SuccessMarkers, "all_events_ok") {
		return ScoreOutput{Category: CategoryAccepted,
			Reasons: []string{"outcomes: all events ok"}, SubScores: subs}
	}
	if gap := numericFromMap(r.ValidationResults, "gap_signals"); gap > 0 {
		return ScoreOutput{Category: CategoryPartiallyAccepted,
			Reasons: []string{fmt.Sprintf("outcomes: %d gap signal(s) detected", int(gap))},
			SubScores: subs}
	}
	return ScoreOutput{Category: CategoryNeedsHumanReview,
		Reasons: []string{"outcomes: no decisive marker — defer to human"},
		SubScores: subs}
}

func scoreModeExperiment(r EvidenceRecord) ScoreOutput {
	subs := &SubScores{}
	if strings.TrimSpace(r.Text) == "" {
		return ScoreOutput{Category: CategoryRejected,
			Reasons: []string{"mode_experiment: empty response text"}, SubScores: subs}
	}
	if r.LatencyMs > 120_000 {
		return ScoreOutput{Category: CategoryPartiallyAccepted,
			Reasons: []string{fmt.Sprintf("mode_experiment: latency %dms exceeds 2-minute soft cap", r.LatencyMs)},
			SubScores: subs}
	}
	return ScoreOutput{Category: CategoryNeedsHumanReview,
		Reasons: []string{"mode_experiment: response present, latency within bounds; verdict not yet wired"},
		SubScores: subs}
}

// ─── Class C: pure-extraction ────────────────────────────────────

func scoreExtraction() ScoreOutput {
	return ScoreOutput{
		Category: CategoryNeedsHumanReview,
		Reasons:  []string{"extraction-class source has no native scoring signal — JOIN to parent verdict pending Phase 3 v2"},
		SubScores: &SubScores{},
	}
}

// ─── Internal helpers ────────────────────────────────────────────

func contains(slice []string, want string) bool {
	for _, s := range slice {
		if s == want {
			return true
		}
	}
	return false
}

func findPrefix(slice []string, prefix string) string {
	for _, s := range slice {
		if strings.HasPrefix(s, prefix) {
			return s
		}
	}
	return ""
}

func findContaining(slice []string, sub string) string {
	for _, s := range slice {
		if strings.Contains(s, sub) {
			return s
		}
	}
	return ""
}

func numericFromMap(m map[string]any, key string) float64 {
	if m == nil {
		return 0
	}
	v, ok := m[key]
	if !ok {
		return 0
	}
	switch n := v.(type) {
	case int:
		return float64(n)
	case int64:
		return float64(n)
	case float32:
		return float64(n)
	case float64:
		return n
	case json.Number:
		f, _ := n.Float64()
		return f
	}
	return 0
}