package db

import (
	"context"
	"crypto/sha256"
	"encoding/hex"
	"encoding/json"
	"log/slog"
	"time"

	"github.com/dtoro/oikos/internal/adapters/postgres/sqlcgen"
	"github.com/dtoro/oikos/internal/core/domain"
	"github.com/dtoro/oikos/internal/core/ports"
	"github.com/dtoro/oikos/internal/observability"
	"github.com/google/uuid"
	"github.com/jackc/pgx/v5"
)

const (
	assentWindowDuration      = 30 * time.Minute
	destructiveWindowDuration = 15 * time.Minute
)

// ApprovalRepo implements ports.ApprovalRepository over the postgres pool.
// Decide verifies the HMAC token (check-then-act), flips the approval,
// un-gates the linked execution, opens assent/destructive windows, flips
// the nomos session out of awaiting_input, and appends audit + event — one
// transaction (ADR 0016 §3.6).
type ApprovalRepo struct {
	pool *Pool
}

var _ ports.ApprovalRepository = (*ApprovalRepo)(nil)

// NewApprovalRepo builds the approval repository.
func NewApprovalRepo(pool *Pool) *ApprovalRepo { return &ApprovalRepo{pool: pool} }

// ListPending returns pending approvals for the given entity (or all pending
// when entityID is empty), newest first.
func (r *ApprovalRepo) ListPending(ctx context.Context, entityID domain.UUID, limit int) ([]domain.Approval, error) {
	if limit <= 0 {
		limit = 50
	}
	if limit > 200 {
		limit = 200
	}
	rows, err := r.pool.Query(ctx, `
		SELECT a.entity_id, COALESCE(a.subject_entity_id::text, ''), a.action, a.risk_class, a.kind,
		       a.payload, a.status, COALESCE(a.token_hash, ''), a.expires_at, a.decided_at,
		       COALESCE(a.decided_by::text, ''), a.created_at
		FROM approvals a
		WHERE ($1::uuid IS NULL OR a.entity_id = $1)
		  AND a.status = 'pending'
		ORDER BY a.created_at DESC
		LIMIT $2`, uuidOrNil(entityID), limit)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	var out []domain.Approval
	for rows.Next() {
		var a domain.Approval
		var subjectStr, tokenHash, decidedBy string
		var payload []byte
		if err := rows.Scan(&a.EntityID, &subjectStr, &a.Action, &a.RiskClass, &a.Kind,
			&payload, &a.Status, &tokenHash, &a.ExpiresAt, &a.DecidedAt,
			&decidedBy, &a.CreatedAt); err != nil {
			return nil, err
		}
		a.TokenHash = tokenHash
		if subjectStr != "" {
			a.SubjectEntityID = domain.UUID(subjectStr)
		}
		if decidedBy != "" {
			a.DecidedBy = domain.UUID(decidedBy)
		}
		if len(payload) > 0 {
			var m map[string]any
			if json.Unmarshal(payload, &m) == nil {
				a.Payload = m
			}
		}
		out = append(out, a)
	}
	return out, rows.Err()
}

// Decide runs the full decide transaction. Returns the updated approval and,
// on approve with a linked execution, the Resume info for the driving adapter
// to dispatch the SSH work after commit.
func (r *ApprovalRepo) Decide(ctx context.Context, in ports.ApprovalDecideInput) (ports.ApprovalDecideResult, error) {
	id := mustUUID(in.ApprovalID)

	tx, err := r.pool.Begin(ctx)
	if err != nil {
		return ports.ApprovalDecideResult{}, err
	}
	defer tx.Rollback(ctx)

	q := sqlcgen.New(tx)

	// Verify HMAC token if provided (single-use, S5).
	if in.Token != "" {
		var tokenHash *string
		var apprStatus string
		var expiresAt time.Time
		err := tx.QueryRow(ctx,
			"SELECT token_hash, status, expires_at FROM approvals WHERE entity_id = $1",
			id).Scan(&tokenHash, &apprStatus, &expiresAt)
		if err != nil || tokenHash == nil {
			return ports.ApprovalDecideResult{}, domain.ErrNotFound
		}
		if apprStatus != "pending" {
			return ports.ApprovalDecideResult{}, domain.ErrInvalidTransition
		}
		if expiresAt.Before(time.Now()) {
			return ports.ApprovalDecideResult{}, domain.ErrInvalidTransition
		}
		if *tokenHash != hashApprovalToken(in.Token) {
			return ports.ApprovalDecideResult{}, domain.ErrInvalidInput
		}
	}

	if err := q.UpdateApprovalStatus(ctx, sqlcgen.UpdateApprovalStatusParams{
		EntityID: id,
		Status:   in.Status,
	}); err != nil {
		return ports.ApprovalDecideResult{}, domain.ErrNotFound
	}

	// Re-read approval.
	app, err := q.GetApprovalByID(ctx, id)
	if err != nil {
		return ports.ApprovalDecideResult{}, err
	}
	approval := domain.Approval{
		EntityID:  domain.UUID(app.EntityID.String()),
		Action:    app.Action,
		RiskClass: app.RiskClass,
		Kind:      app.Kind,
		Status:    app.Status,
		TokenHash: stringPtrOr(app.TokenHash),
		ExpiresAt: app.ExpiresAt,
		DecidedAt: app.DecidedAt,
		DecidedBy: uuidPtrOr(app.DecidedBy),
		CreatedAt: app.CreatedAt,
	}
	if app.SubjectEntityID != nil {
		approval.SubjectEntityID = domain.UUID(app.SubjectEntityID.String())
	}

	// Audit + event (in-tx; NOTIFY fires post-commit). An audit failure must
	// abort the decision — leaving no trace of who decided would violate the
	// append-only audit contract (ADR 0016 §3.6).
	actorLabel := in.Actor
	if actorLabel == "" {
		actorLabel = "unknown"
	}
	if auditErr := observability.Audit(ctx, q, "api", actorLabel, "decide",
		&id, "POST", "/api/v1/approvals/"+id.String()+"/decision", "",
		nil,
		map[string]any{"decision": in.Status}); auditErr != nil {
		return ports.ApprovalDecideResult{}, auditErr
	}
	if evErr := observability.Event(ctx, q, "approval.decided", &id, "info", "api", "",
		map[string]any{"decision": in.Status, "actor": actorLabel}); evErr != nil {
		return ports.ApprovalDecideResult{}, evErr
	}

	result := ports.ApprovalDecideResult{Approval: approval}

	// Approve: un-gate the linked execution and open windows.
	if in.Status == "approved" {
		resume, aerr := r.approveSideEffects(ctx, tx, id)
		if aerr != nil {
			return result, aerr
		}
		result.Resume = resume
	} else {
		// Denied/revoked: reflect on the linked execution.
		_, _ = tx.Exec(ctx, `UPDATE executions SET status = $2, completed_at = now() WHERE approval_id = $1 AND status = 'pending_approval'`, id, in.Status)
	}

	// Flip any nomos session out of awaiting_input — the operator answered.
	flipAwaitingSession(ctx, tx, id, in.Status)

	if err := tx.Commit(ctx); err != nil {
		return result, err
	}
	return result, nil
}

// approveSideEffects finds the linked pending execution, marks it approved,
// opens the assent window (+ destructive window for destructive risk), and
// returns the Resume info for the adapter to dispatch the SSH work.
func (r *ApprovalRepo) approveSideEffects(ctx context.Context, tx pgx.Tx, approvalID uuid.UUID) (*ports.ApprovalResume, error) {
	var execID, targetID uuid.UUID
	var actionStr, targetSlug, riskClass, sessionID string
	err := tx.QueryRow(ctx, `
		SELECT e.entity_id, e.target_entity_id, e.action, e.risk_class,
		       COALESCE((SELECT pe.session_id FROM nomos_plan_executions pe
		                 WHERE pe.execution_id = e.entity_id LIMIT 1)::text, '')
		FROM executions e
		WHERE e.approval_id = $1 AND e.status = 'pending_approval'
		LIMIT 1`, approvalID).Scan(&execID, &targetID, &actionStr, &riskClass, &sessionID)
	if err != nil {
		slog.Warn("postgres: no pending execution found for approval", "approval_id", approvalID, "error", err)
		return nil, nil
	}

	_ = tx.QueryRow(ctx, "SELECT slug FROM entities WHERE id = $1", targetID).Scan(&targetSlug)

	// Status only — risk_class was set correctly at request time (e.g. by
	// policy.ClassifyCommand for `run`); overwriting it to a hardcoded
	// 'config_mutation' here corrupted the audit ledger for every other risk
	// class, including destructive.
	_, _ = tx.Exec(ctx, `UPDATE executions SET status = 'approved' WHERE entity_id = $1`, execID)

	var agentID *uuid.UUID
	if qerr := tx.QueryRow(ctx, "SELECT agent_id FROM executions WHERE entity_id = $1", execID).Scan(&agentID); qerr == nil && agentID != nil {
		// Approving a plan step — by ANY route (the UI Approve button and
		// chat-assent) — opens/extends the agent's assent window. The key is
		// session-scoped so the window only auto-runs THIS task's plan steps
		// (governance.go AssentWindowActive + session store's AssentWindowKey
		// use the same "assent_window.agent:<id>.session:<sid>" format).
		expires := time.Now().Add(assentWindowDuration).UTC().Format(time.RFC3339)
		_, _ = tx.Exec(ctx, `INSERT INTO autonomy_settings (key, value) VALUES ($1, $2)
			ON CONFLICT (key) DO UPDATE SET value = $2`,
			"assent_window.agent:"+agentID.String()+".session:"+sessionID, expires)

		// Approving a DESTRUCTIVE step via the button is exactly as explicit
		// as a typed "I confirm" — open the same short, target+session-scoped
		// destructive window chat-assent's typed-confirm path opens.
		if riskClass == "destructive" && targetSlug != "" {
			dExpires := time.Now().Add(destructiveWindowDuration).UTC().Format(time.RFC3339)
			_, _ = tx.Exec(ctx, `INSERT INTO autonomy_settings (key, value) VALUES ($1, $2)
				ON CONFLICT (key) DO UPDATE SET value = $2`,
				"destructive_window.agent:"+agentID.String()+".target:"+targetSlug+".session:"+sessionID, dExpires)
		}
	}

	slog.Info("postgres: approved execution queued",
		"execution_id", execID, "target", targetSlug, "action", actionStr)
	return &ports.ApprovalResume{
		ExecutionID: domain.UUID(execID.String()),
		TargetSlug:  targetSlug,
		Action:      actionStr,
	}, nil
}

// flipAwaitingSession marks any nomos session linked to this approval as
// executing again (awaiting_input → executing), mirroring
// classifyAndGate's awaiting_input flip in reverse.
func flipAwaitingSession(ctx context.Context, tx pgx.Tx, approvalID uuid.UUID, status string) {
	var awaitingSessionID string
	_ = tx.QueryRow(ctx, `
		SELECT pe.session_id FROM nomos_plan_executions pe
		JOIN executions ex ON ex.entity_id = pe.execution_id
		WHERE ex.approval_id = $1
		LIMIT 1`, approvalID).Scan(&awaitingSessionID)
	if awaitingSessionID == "" {
		return
	}
	rtag, rerr := tx.Exec(ctx, `
		UPDATE agent_sessions SET status = 'executing', last_active_at = now()
		WHERE id = $1 AND status = 'awaiting_input'`, awaitingSessionID)
	if rerr != nil || rtag.RowsAffected() == 0 {
		return
	}
	var taskEntID *uuid.UUID
	var e uuid.UUID
	if qerr := tx.QueryRow(ctx, `SELECT entity_id FROM agent_sessions WHERE id = $1`, awaitingSessionID).Scan(&e); qerr == nil && e != uuid.Nil {
		taskEntID = &e
	}
	_ = observability.Event(ctx, sqlcgen.New(tx), "task.status", taskEntID, "info", "api", awaitingSessionID,
		map[string]any{"status": "executing", "reason": "approval_decided", "decision": status})
}

// hashApprovalToken computes a SHA-256 hex-encoded hash of the token, used
// to verify single-use approval tokens (S5) without storing the plaintext.
func hashApprovalToken(token string) string {
	h := sha256.Sum256([]byte(token))
	return hex.EncodeToString(h[:])
}

func uuidOrNil(id domain.UUID) any {
	if id == "" {
		return nil
	}
	return mustUUID(id)
}

func stringPtrOr(s *string) string {
	if s == nil {
		return ""
	}
	return *s
}

func uuidPtrOr(u *uuid.UUID) domain.UUID {
	if u == nil {
		return ""
	}
	return domain.UUID(u.String())
}