package store

import (
	"encoding/json"
	"sort"
	"strings"

	"orchestra/internal/domain"
	"orchestra/internal/review"
)

// ProjectDebt folds canonical history into a debt ledger. It is a pure
// function of the events so it can be tested against a real log, and it writes
// nothing: this projection is a read model, not a new kind of truth.
//
// It deliberately reports what it cannot see. Worker observations and operator
// interventions are not carried by any event type today, so a ledger that
// stayed silent about them would read as "no operational cost" when it means
// "operational cost is unrecorded".
func ProjectDebt(events []domain.Event) domain.DebtLedger {
	return projectDebt(events, nil)
}

// ProjectDebtWithArtifacts is ProjectDebt plus the CAS reads that review
// findings need. Findings are sealed as an artifact rather than inlined in the
// event, and they are the only evidence structural debt has, so a projection
// without them can never produce a structural item at all.
func ProjectDebtWithArtifacts(events []domain.Event, read func(ref string) ([]byte, error)) domain.DebtLedger {
	return projectDebt(events, read)
}

func projectDebt(events []domain.Event, readArtifact func(string) ([]byte, error)) domain.DebtLedger {
	bySignature := map[string]*domain.DebtItem{}
	order := []string{}
	seenKinds := map[domain.ObservationKind]bool{}

	add := func(class domain.DebtClass, sig string, o domain.DebtObservation, symptom string, sev review.Severity) {
		o.Signature = sig
		if o.Validate() != nil {
			return
		}
		seenKinds[o.Kind] = true
		item, ok := bySignature[sig]
		if !ok {
			item = &domain.DebtItem{
				// The id is the signature, not an Fxx number. This projection
				// produces candidates from history; adopting a curated id is a
				// later, deliberate step, and minting one here would collide
				// with the hand-written ledger.
				ID: sig, Class: class, Status: domain.DebtObserved,
				Symptom: symptom, Signatures: []string{sig}, Severity: sev,
			}
			bySignature[sig] = item
			order = append(order, sig)
		}
		item.Observations = append(item.Observations, o)
		for _, p := range o.Paths {
			if !contains(item.Paths, p) {
				item.Paths = append(item.Paths, p)
			}
		}
	}

	for _, e := range events {
		var p map[string]any
		if len(e.Payload) > 0 && json.Unmarshal(e.Payload, &p) != nil {
			continue
		}
		base := domain.DebtObservation{EventID: e.ID, TaskID: e.TaskID, At: e.At}
		harness, _ := p["harness_id"].(string)
		switch e.Type {
		case "TaskBlocked":
			reason, _ := p["block_reason"].(string)
			if reason == "" {
				reason = string(domain.InferBlockReason(str(p["blocker"])))
			}
			class, ok := domain.DebtClassForBlockReason(domain.BlockReason(reason))
			if !ok {
				continue
			}
			o := base
			o.Kind = domain.ObservationBlockReason
			o.Detail = str(p["blocker"])
			add(class, domain.DebtSignature(class, reason, harness, "lease"), o,
				"tasks are blocked with "+reason, review.Important)
		case "TaskFailed", "TaskReleased":
			// A release carries a failure class only when it is a reclaim. A
			// handoff release is ordinary progress and never debt.
			failure, _ := p["failure_class"].(string)
			if failure == "" {
				failure, _ = p["reason"].(string)
			}
			if e.Type == "TaskReleased" && str(p["handoff_ref"]) != "" {
				continue
			}
			class, ok := domain.DebtClassForFailureClass(failure)
			if !ok {
				continue
			}
			o := base
			o.Kind = domain.ObservationFailureClass
			o.Detail = str(p["last_error"])
			add(class, domain.DebtSignature(class, failure, harness, "lease"), o,
				"tasks end in "+failure, review.Important)
		case domain.EventObservationIncidentClosed:
			// One incident, whatever it repeated. The debt class comes from
			// the signature's shape rather than a failure class, because a
			// worker observation is a symptom the worker described, not a
			// lifecycle outcome Orchestra decided.
			var inc domain.ObservationIncident
			if json.Unmarshal(e.Payload, &inc) != nil || inc.Signature == "" {
				continue
			}
			o := base
			o.Kind = domain.ObservationWorkerFailure
			o.TaskID = inc.TaskID
			o.Detail = inc.Detail
			o.Repeats = inc.RepeatCount
			add(domain.DebtOperational,
				domain.DebtSignature(domain.DebtOperational, inc.Signature, inc.WorkerID, "worker"),
				o, "workers report "+inc.Signature, review.Important)
		case domain.EventOperatorInterventionRecorded:
			var in domain.OperatorIntervention
			if json.Unmarshal(e.Payload, &in) != nil || !in.Kind.Valid() {
				continue
			}
			o := base
			o.Kind = domain.ObservationManualIntervention
			o.TaskID = in.TaskID
			o.Detail = in.Reason
			o.Paths = in.Components
			add(domain.DebtOperational,
				domain.DebtSignature(domain.DebtOperational, string(in.Kind), in.WorkerID, "manual"),
				o, "an operator repairs this by hand ("+string(in.Kind)+")", review.Important)
		case domain.EventPlanMismatchRecorded:
			o := base
			o.Kind = domain.ObservationPlanMismatch
			o.Detail = str(p["observed"])
			o.Paths = strList(p["evidence"])
			component := firstComponent(o.Paths)
			add(domain.DebtCorrectness,
				domain.DebtSignature(domain.DebtCorrectness, "plan_mismatch", "", component), o,
				"the repository contradicts sealed plans", review.Important)
		case domain.EventReviewRecorded:
			// Repeated findings in one component are the only mechanical
			// evidence that structure is costing future changes. One finding
			// is a review doing its job.
			if readArtifact == nil {
				break
			}
			raw, err := readArtifact(str(p["artifact_ref"]))
			if err != nil {
				break
			}
			result, err := review.Decode(raw)
			if err != nil {
				break
			}
			for _, f := range result.Findings {
				component := domain.DebtComponent(f.File)
				o := base
				o.Kind = domain.ObservationReviewFinding
				o.Detail = f.Claim
				if f.File != "" {
					o.Paths = []string{f.File}
				}
				add(domain.DebtStructural,
					domain.DebtSignature(domain.DebtStructural, string(f.Severity), "", component), o,
					"review keeps finding "+string(f.Severity)+" issues in "+component, f.Severity)
			}
		case domain.EventDeferredFindingRecorded:
			o := base
			o.Kind = domain.ObservationDeferredFinding
			o.Detail = str(p["summary"])
			// Polish until something demonstrates a cost. A discovery nobody
			// has paid for yet is not debt with a priority.
			add(domain.DebtPolish,
				domain.DebtSignature(domain.DebtPolish, "deferred_finding", "", ""), o,
				"out-of-scope discoveries recorded and unaddressed", review.Minor)
		}
	}

	items := make([]domain.DebtItem, 0, len(order))
	for _, sig := range order {
		items = append(items, *bySignature[sig])
	}
	sort.SliceStable(items, func(i, j int) bool {
		if items[i].Recurrence() != items[j].Recurrence() {
			return items[i].Recurrence() > items[j].Recurrence()
		}
		return items[i].ID < items[j].ID
	})
	return domain.DebtLedger{Items: items, Gaps: debtGaps(seenKinds), Events: len(events)}
}

// debtGaps separates two different silences. A kind no event type carries is a
// hole in the system. A kind the log could carry and does not is a fact about
// this history.
func debtGaps(seen map[domain.ObservationKind]bool) []domain.EvidenceGap {
	// Both of these were once permanent holes in the system. They are ordinary
	// evidence now, so their absence is a fact about this history rather than
	// about Orchestra.
	var gaps []domain.EvidenceGap
	for _, k := range []domain.ObservationKind{
		domain.ObservationBlockReason, domain.ObservationFailureClass,
		domain.ObservationReviewFinding, domain.ObservationPlanMismatch,
		domain.ObservationDeferredFinding, domain.ObservationWorkerFailure,
		domain.ObservationManualIntervention,
	} {
		if !seen[k] {
			gaps = append(gaps, domain.EvidenceGap{Kind: k, Durable: true,
				Reason: "carried by the log, but this history contains none"})
		}
	}
	return gaps
}

// DebtLedger projects the whole log. Read-only, like every other projection
// the coordinator serves.
func (s *Store) DebtLedger() domain.DebtLedger {
	return ProjectDebtWithArtifacts(s.Events(0), s.Artifact)
}

func str(v any) string { s, _ := v.(string); return s }

func strList(v any) []string {
	list, ok := v.([]any)
	if !ok {
		return nil
	}
	out := make([]string, 0, len(list))
	for _, item := range list {
		if s := strings.TrimSpace(str(item)); s != "" {
			out = append(out, s)
		}
	}
	return out
}

func firstComponent(paths []string) string {
	for _, p := range paths {
		if c := domain.DebtComponent(p); c != "" {
			return c
		}
	}
	return ""
}

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