package capture

import (
	"context"
	"crypto/sha256"
	"encoding/hex"
	"fmt"
	"strings"
	"time"

	"github.com/mathiasbq/hyperguild/ingestion/internal/brain"
	"github.com/mathiasbq/hyperguild/ingestion/internal/classification"
)

// Service is the CaptureSession use-case. It depends only on ports.
type Service struct {
	brain     BrainStore
	issues    IssueTracker
	summaries SummaryWriter
	policy    ClassificationPolicy
	audit     AuditSink

	// now is the clock, injectable for deterministic summary paths and
	// audit timestamps in tests.
	now func() time.Time
}

// NewService constructs a Service from its ports. summaries may be nil
// when no summary persistence is wired; a CaptureInput with a Summary
// then fails that item rather than panicking.
func NewService(b BrainStore, tr IssueTracker, sw SummaryWriter, p ClassificationPolicy, a AuditSink) *Service {
	return &Service{brain: b, issues: tr, summaries: sw, policy: p, audit: a, now: time.Now}
}

var validActions = map[string]bool{"create": true, "close": true, "comment": true}

// ErrSovereigntyRefused is returned when the I1 gate refuses a capture
// (confidential effective classification through a us-nexus origin). The
// REST adapter maps it to HTTP 403. Callers test with errors.Is.
var ErrSovereigntyRefused = fmt.Errorf("capture refused by I1 sovereignty gate")

// ErrAuditUnavailable is returned when the I5 audit gate refuses a capture
// before any write: a confidential capture whose central audit sink is
// unreachable, or the all-tiers floor where nothing can record the audit.
// The REST adapter maps it to HTTP 503. Callers test with errors.Is.
var ErrAuditUnavailable = fmt.Errorf("capture refused: audit substrate unavailable")

// assertedZoneMismatch returns a security-event string when the caller's
// harness label asserts a trust zone that contradicts the server-derived
// origin. A harness label that names no zone (the normal case, e.g.
// "claude-code") returns "". The label is never used as a gate input —
// this only flags the discrepancy for the audit trail.
func assertedZoneMismatch(harness string, derived Zone) string {
	var asserted Zone
	switch strings.ToLower(strings.TrimSpace(harness)) {
	case "sovereign-soil", "sovereign":
		asserted = ZoneSovereign
	case "us-nexus", "usnexus":
		asserted = ZoneUSNexus
	default:
		return "" // no zone claim
	}
	if asserted != derived {
		return fmt.Sprintf("asserted-vs-derived origin mismatch: harness asserted %s, principal resolves to %s",
			asserted, derived)
	}
	return ""
}

// Capture runs the use-case: validate (fail-closed), resolve effective
// classification (stricter of declared vs target-derived), then persist
// insights → tickets → summary best-effort, emit an audit record, and
// return a partial-aware receipt.
//
// A validation failure returns a non-nil error with nothing written. A
// per-item execution failure is recorded in the receipt (no rollback);
// the call still returns a nil error so the caller gets the partial
// receipt. The I1 origin gate and audit-down degradation are layered on
// by #53/#54 around this core.
func (s *Service) Capture(ctx context.Context, in CaptureInput) (CaptureReceipt, error) {
	if err := s.validate(in); err != nil {
		return CaptureReceipt{}, err
	}

	declared := classification.Public // unspecified ⇒ lowest ⇒ target floor governs
	if in.Context.Classification != "" {
		// Already validated parseable.
		declared, _ = classification.ParseLevel(in.Context.Classification)
	}

	effective, securityEvents := s.resolveClassification(declared, in)

	// Server-derived origin governs the I1 gate; a caller-asserted harness
	// label that names a different zone is descriptive-only and logged as a
	// security event (spec §4.2: a control keyed on attacker-suppliable
	// input is not a control).
	if ev := assertedZoneMismatch(in.Context.Harness, in.Context.Origin); ev != "" {
		securityEvents = append(securityEvents, ev)
	}

	// I1 sovereignty gate: a confidential capture through a us-nexus origin
	// is refused before ANY write. The refusal itself is audited (best
	// effort) — refusals must be reconstructable too.
	if effective == classification.Confidential && in.Context.Origin == ZoneUSNexus {
		_ = s.audit.Record(ctx, AuditEntry{
			Timestamp:               s.now().UTC(),
			Principal:               in.Context.Principal,
			Actor:                   in.Context.Actor,
			Harness:                 in.Context.Harness,
			SessionRef:              in.Context.SessionRef,
			EffectiveClassification: effective.String(),
			Items:                   nil, // refused before any write
			SecurityEvents:          append(securityEvents, "I1 refusal: confidential capture via us-nexus origin"),
		}, AuditCentral)
		return CaptureReceipt{}, fmt.Errorf("%w: effective classification confidential through %s origin",
			ErrSovereigntyRefused, in.Context.Origin)
	}

	receipt := CaptureReceipt{
		Errors:                  []ItemError{},
		EffectiveClassification: effective.String(),
		DryRun:                  in.DryRun,
	}

	if in.DryRun {
		// Would-be receipt: mark planned items ok, write nothing (not even
		// audit — dry_run touches nothing).
		for range in.Insights {
			receipt.Insights = append(receipt.Insights, InsightResult{OK: true})
		}
		for _, tk := range in.Tickets {
			receipt.Tickets = append(receipt.Tickets, TicketResult{Repo: tk.Repo, Action: tk.Action, Number: tk.Number, OK: true})
		}
		if in.Summary != nil {
			receipt.Summary = &SummaryResult{Path: s.summaryPath(in.Context, in.Summary), OK: true}
		}
		return receipt, nil
	}

	// I5 audit gate: decide BEFORE any write whether this capture can be
	// audited at its effective classification. Confidential + central sink
	// down → refuse here, before writing anything; the all-tiers floor
	// (nothing can record) likewise refuses. Internal/public degrade to the
	// durable local buffer (signalled by AuditBuffered).
	outcome, err := s.audit.Reserve(ctx, effective)
	if err != nil {
		return CaptureReceipt{}, fmt.Errorf("%w: %v", ErrAuditUnavailable, err)
	}

	var landed []string

	for i, ins := range in.Insights {
		res, item, err := s.persistInsight(ctx, ins)
		receipt.Insights = append(receipt.Insights, res)
		if err != nil {
			receipt.Errors = append(receipt.Errors, ItemError{Item: fmt.Sprintf("insight[%d]", i), Error: err.Error()})
			continue
		}
		landed = append(landed, item)
	}

	for i, tk := range in.Tickets {
		res, err := s.persistTicket(ctx, tk)
		receipt.Tickets = append(receipt.Tickets, res)
		if err != nil {
			receipt.Errors = append(receipt.Errors, ItemError{Item: fmt.Sprintf("ticket[%d]", i), Error: err.Error()})
			continue
		}
		landed = append(landed, fmt.Sprintf("ticket:%s#%d", tk.Repo, res.Number))
	}

	if in.Summary != nil {
		res, err := s.persistSummary(ctx, in.Context, in.Summary)
		receipt.Summary = &res
		if err != nil {
			receipt.Errors = append(receipt.Errors, ItemError{Item: "summary", Error: err.Error()})
		} else {
			landed = append(landed, "summary:"+res.Path)
		}
	}

	// I5: persist the request-level audit record of exactly what landed,
	// using the outcome reserved before the writes. AuditBuffered surfaces
	// the degraded (locally-buffered) state on the receipt.
	if err := s.audit.Record(ctx, AuditEntry{
		Timestamp:               s.now().UTC(),
		Principal:               in.Context.Principal,
		Actor:                   in.Context.Actor,
		Harness:                 in.Context.Harness,
		SessionRef:              in.Context.SessionRef,
		EffectiveClassification: effective.String(),
		Items:                   landed,
		SecurityEvents:          securityEvents,
	}, outcome); err != nil {
		receipt.Errors = append(receipt.Errors, ItemError{Item: "audit", Error: err.Error()})
	}
	if outcome == AuditBuffered {
		receipt.AuditBuffered = true
	}

	return receipt, nil
}

// validate enforces fail-closed structural validity over the whole
// request before any write. A bad declared classification, an invalid
// wing/hall, an empty insight, or a malformed ticket aborts the capture
// with nothing written.
func (s *Service) validate(in CaptureInput) error {
	if in.Context.Classification != "" {
		if _, err := classification.ParseLevel(in.Context.Classification); err != nil {
			return fmt.Errorf("context.classification: %w", err)
		}
	}
	for i, ins := range in.Insights {
		if strings.TrimSpace(ins.Text) == "" {
			return fmt.Errorf("insight[%d]: text is required", i)
		}
		if strings.TrimSpace(ins.Wing) == "" {
			return fmt.Errorf("insight[%d]: wing is required", i)
		}
		if !brain.IsValidHall(ins.Hall) {
			return fmt.Errorf("insight[%d]: invalid hall %q", i, ins.Hall)
		}
	}
	for i, tk := range in.Tickets {
		if strings.TrimSpace(tk.Repo) == "" {
			return fmt.Errorf("ticket[%d]: repo is required", i)
		}
		if !validActions[tk.Action] {
			return fmt.Errorf("ticket[%d]: invalid action %q (want create/close/comment)", i, tk.Action)
		}
		if tk.Action == "create" && strings.TrimSpace(tk.Title) == "" {
			return fmt.Errorf("ticket[%d]: create requires a title", i)
		}
		if (tk.Action == "close" || tk.Action == "comment") && tk.Number <= 0 {
			return fmt.Errorf("ticket[%d]: %s requires an issue number", i, tk.Action)
		}
	}
	return nil
}

// resolveClassification computes the effective level (stricter of
// declared and every target's derived level) and collects a security
// event whenever the caller under-declared relative to a target floor.
func (s *Service) resolveClassification(declared classification.Level, in CaptureInput) (classification.Level, []string) {
	effective := declared
	var events []string
	consider := func(kind classification.TargetKind, name string) {
		derived := s.policy.Derive(classification.Target{Kind: kind, Name: name})
		effective = classification.Stricter(effective, derived)
		if declared < derived {
			events = append(events, fmt.Sprintf("classification under-declared: declared=%s target=%s(%s) derived=%s",
				declared, name, kindString(kind), derived))
		}
	}
	for _, ins := range in.Insights {
		consider(classification.WingTarget, ins.Wing)
	}
	for _, tk := range in.Tickets {
		consider(classification.RepoTarget, tk.Repo)
	}
	if in.Summary != nil {
		for _, repo := range in.Summary.ReposTouched {
			consider(classification.RepoTarget, repo)
		}
	}
	return effective, events
}

func (s *Service) persistInsight(ctx context.Context, ins Insight) (InsightResult, string, error) {
	note := Note{Content: ins.Text, Wing: ins.Wing, Hall: ins.Hall, Filename: brain.Sanitise(firstLine(ins.Text))}
	var ref Ref
	var err error
	if ins.SupersedeSlug != "" {
		note.Reason = "superseded via capture"
		ref, err = s.brain.Update(ctx, ins.SupersedeSlug, note)
	} else {
		ref, err = s.brain.Write(ctx, note)
	}
	if err != nil {
		return InsightResult{OK: false, Superseded: ins.SupersedeSlug != ""}, "", err
	}
	return InsightResult{
		ID: ref.ID, Path: ref.Path, ContentHash: ref.ContentHash,
		Superseded: ref.Superseded, OK: true,
	}, "insight:" + ref.ID, nil
}

func (s *Service) persistTicket(ctx context.Context, tk Ticket) (TicketResult, error) {
	res := TicketResult{Repo: tk.Repo, Action: tk.Action, Number: tk.Number}
	var ref IssueRef
	var err error
	switch tk.Action {
	case "create":
		ref, err = s.issues.CreateIssue(ctx, tk.Repo, tk.Title, tk.Body)
	case "close":
		ref, err = s.issues.CloseIssue(ctx, tk.Repo, tk.Number, tk.Body)
	case "comment":
		ref, err = s.issues.CommentIssue(ctx, tk.Repo, tk.Number, tk.Body)
	}
	if err != nil {
		return res, err
	}
	if ref.Number != 0 {
		res.Number = ref.Number
	}
	res.URL = ref.URL
	res.OK = true
	return res, nil
}

func (s *Service) persistSummary(ctx context.Context, c CaptureContext, sum *Summary) (SummaryResult, error) {
	if s.summaries == nil {
		return SummaryResult{OK: false}, fmt.Errorf("no summary writer configured")
	}
	path := s.summaryPath(c, sum)
	content := s.renderSummary(c, sum)
	repo := "ai-sessions"
	if err := s.summaries.WriteFile(ctx, repo, path, content); err != nil {
		return SummaryResult{Path: path, OK: false}, err
	}
	return SummaryResult{Path: path, OK: true}, nil
}

// summaryPath builds summaries/<harness>/<YYYY-MM>/<date>-<slug>-<ref8>.md.
// The ref8 disambiguator is derived from the session_ref (or the title
// when no ref is present) so distinct sessions never collide.
func (s *Service) summaryPath(c CaptureContext, sum *Summary) string {
	t := s.now().UTC()
	slug := brain.Sanitise(sum.Title)
	if slug == "" {
		slug = "summary"
	}
	seed := c.SessionRef
	if seed == "" {
		seed = sum.Title + sum.Body
	}
	sum8 := shortHash(seed)
	return fmt.Sprintf("summaries/%s/%s/%s-%s-%s.md",
		brain.Sanitise(c.Harness), t.Format("2006-01"), t.Format("2006-01-02"), slug, sum8)
}

// renderSummary stamps fidelity + session metadata into frontmatter so the
// richer-fidelity-supersedes-thinner collision rule has the data it needs.
func (s *Service) renderSummary(c CaptureContext, sum *Summary) string {
	var b strings.Builder
	b.WriteString("---\n")
	fmt.Fprintf(&b, "title: %s\n", sum.Title)
	fmt.Fprintf(&b, "harness: %s\n", c.Harness)
	if c.SessionRef != "" {
		fmt.Fprintf(&b, "session_ref: %s\n", c.SessionRef)
	}
	fmt.Fprintf(&b, "fidelity: %s\n", c.Fidelity)
	fmt.Fprintf(&b, "captured_at: %s\n", s.now().UTC().Format(time.RFC3339))
	if len(sum.ReposTouched) > 0 {
		fmt.Fprintf(&b, "repos_touched: [%s]\n", strings.Join(sum.ReposTouched, ", "))
	}
	b.WriteString("---\n\n")
	b.WriteString(sum.Body)
	if !strings.HasSuffix(sum.Body, "\n") {
		b.WriteByte('\n')
	}
	return b.String()
}

func kindString(k classification.TargetKind) string {
	if k == classification.RepoTarget {
		return "repo"
	}
	return "wing"
}

func firstLine(s string) string {
	s = strings.TrimSpace(s)
	if i := strings.IndexByte(s, '\n'); i >= 0 {
		s = s[:i]
	}
	s = strings.TrimLeft(s, "# ")
	if len(s) > 60 {
		s = s[:60]
	}
	return s
}

func shortHash(s string) string {
	sum := sha256.Sum256([]byte(s))
	return hex.EncodeToString(sum[:])[:8]
}