package docgov

import (
	"context"
	"fmt"
	"strings"
	"time"

	"github.com/jackc/pgx/v5"
)

const (
	PendingSupplementPending   = "pending"
	PendingSupplementDigested  = "digested"
	PendingSupplementDiscarded = "discarded"
)

// PendingSupplement is one locked-period fact supplement deferred for later digestion.
type PendingSupplement struct {
	ID              int64      `json:"id"`
	DocID           string     `json:"doc_id"`
	ProjectID       int64      `json:"project_id"`
	SourceSummary   string     `json:"source_summary"`
	ImpactReason    string     `json:"impact_reason"`
	InitiatorUserID int64      `json:"initiator_user_id"`
	BatchID         string     `json:"batch_id,omitempty"`
	Status          string     `json:"status"`
	DigestedAt      *time.Time `json:"digested_at,omitempty"`
	DecidedBy       int64      `json:"decided_by,omitempty"`
	CreatedAt       time.Time  `json:"created_at"`
}

// PendingSupplementNotify is invoked after pending rows are marked digested.
type PendingSupplementNotify func(ctx context.Context, doc *DocumentRecord, pending []PendingSupplement)

// RecordPendingSupplementInput captures a supplement that cannot be applied while locked.
type RecordPendingSupplementInput struct {
	DocID           string
	ProjectID       int64
	InitiatorUserID int64
	SourceSummary   string
	ImpactReason    string
	BatchID         string
}

// RecordPendingSupplement persists a deferred supplement for a locked document.
func (e *GovernanceEngine) RecordPendingSupplement(ctx context.Context, in RecordPendingSupplementInput) (*PendingSupplement, error) {
	if e == nil {
		return nil, fmt.Errorf("docgov: engine required")
	}
	docID := strings.TrimSpace(in.DocID)
	if docID == "" || in.ProjectID <= 0 {
		return nil, fmt.Errorf("docgov: pending supplement requires doc_id and project_id")
	}
	now := time.Now().UTC()
	row := &PendingSupplement{
		DocID: docID, ProjectID: in.ProjectID, InitiatorUserID: in.InitiatorUserID,
		SourceSummary: strings.TrimSpace(in.SourceSummary),
		ImpactReason:  strings.TrimSpace(in.ImpactReason),
		BatchID:       strings.TrimSpace(in.BatchID),
		Status:        PendingSupplementPending,
		CreatedAt:     now,
	}
	if e.pool == nil {
		return row, nil
	}
	err := e.pool.QueryRow(ctx, `
		INSERT INTO document_pending_supplements (
		  doc_id, project_id, source_summary, impact_reason, initiator_user_id, batch_id, status, created_at, updated_at
		) VALUES ($1,$2,$3,$4,$5,$6,$7,$8,$8)
		RETURNING id, created_at
	`, row.DocID, row.ProjectID, row.SourceSummary, row.ImpactReason, row.InitiatorUserID, row.BatchID, row.Status, now).
		Scan(&row.ID, &row.CreatedAt)
	if err != nil {
		return nil, fmt.Errorf("docgov: record pending supplement: %w", err)
	}
	return row, nil
}

// ListPendingSupplements returns pending rows for a document.
func (e *GovernanceEngine) ListPendingSupplements(ctx context.Context, docID string) ([]PendingSupplement, error) {
	if e == nil || e.pool == nil {
		return nil, nil
	}
	docID = strings.TrimSpace(docID)
	if docID == "" {
		return nil, nil
	}
	rows, err := e.pool.Query(ctx, `
		SELECT id, doc_id, project_id, source_summary, impact_reason, initiator_user_id, batch_id,
		       status, digested_at, decided_by, created_at
		FROM document_pending_supplements
		WHERE doc_id = $1 AND status = $2
		ORDER BY created_at ASC, id ASC
	`, docID, PendingSupplementPending)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	out := make([]PendingSupplement, 0)
	for rows.Next() {
		var p PendingSupplement
		if err := rows.Scan(
			&p.ID, &p.DocID, &p.ProjectID, &p.SourceSummary, &p.ImpactReason, &p.InitiatorUserID, &p.BatchID,
			&p.Status, &p.DigestedAt, &p.DecidedBy, &p.CreatedAt,
		); err != nil {
			return nil, err
		}
		out = append(out, p)
	}
	return out, rows.Err()
}

// ListPendingSupplementsByProject returns undigested pending rows for a project (optional doc filter).
func (e *GovernanceEngine) ListPendingSupplementsByProject(ctx context.Context, projectID int64, docID string) ([]PendingSupplement, error) {
	if e == nil || e.pool == nil || projectID <= 0 {
		return nil, nil
	}
	docID = strings.TrimSpace(docID)
	var rows pgx.Rows
	var err error
	if docID != "" {
		rows, err = e.pool.Query(ctx, `
			SELECT id, doc_id, project_id, source_summary, impact_reason, initiator_user_id, batch_id,
			       status, digested_at, decided_by, created_at
			FROM document_pending_supplements
			WHERE project_id = $1 AND doc_id = $2 AND status = $3
			ORDER BY created_at ASC, id ASC
		`, projectID, docID, PendingSupplementPending)
	} else {
		rows, err = e.pool.Query(ctx, `
			SELECT id, doc_id, project_id, source_summary, impact_reason, initiator_user_id, batch_id,
			       status, digested_at, decided_by, created_at
			FROM document_pending_supplements
			WHERE project_id = $1 AND status = $2
			ORDER BY created_at ASC, id ASC
		`, projectID, PendingSupplementPending)
	}
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	out := make([]PendingSupplement, 0)
	for rows.Next() {
		var p PendingSupplement
		if err := rows.Scan(
			&p.ID, &p.DocID, &p.ProjectID, &p.SourceSummary, &p.ImpactReason, &p.InitiatorUserID, &p.BatchID,
			&p.Status, &p.DigestedAt, &p.DecidedBy, &p.CreatedAt,
		); err != nil {
			return nil, err
		}
		out = append(out, p)
	}
	return out, rows.Err()
}

// DigestPendingSupplements marks all pending rows digested when a document returns to drafting.
// It returns the digested rows so callers can notify the author.
func (e *GovernanceEngine) DigestPendingSupplements(ctx context.Context, docID string, decidedBy int64) ([]PendingSupplement, error) {
	if e == nil {
		return nil, fmt.Errorf("docgov: engine required")
	}
	docID = strings.TrimSpace(docID)
	if docID == "" {
		return nil, nil
	}
	pending, err := e.ListPendingSupplements(ctx, docID)
	if err != nil || len(pending) == 0 {
		return pending, err
	}
	if e.pool == nil {
		for i := range pending {
			pending[i].Status = PendingSupplementDigested
			now := time.Now().UTC()
			pending[i].DigestedAt = &now
			pending[i].DecidedBy = decidedBy
		}
		return pending, nil
	}
	now := time.Now().UTC()
	_, err = e.pool.Exec(ctx, `
		UPDATE document_pending_supplements
		SET status = $2, digested_at = $3, decided_by = $4, updated_at = $3
		WHERE doc_id = $1 AND status = $5
	`, docID, PendingSupplementDigested, now, decidedBy, PendingSupplementPending)
	if err != nil {
		return nil, fmt.Errorf("docgov: digest pending supplements: %w", err)
	}
	for i := range pending {
		pending[i].Status = PendingSupplementDigested
		pending[i].DigestedAt = &now
		pending[i].DecidedBy = decidedBy
	}
	return pending, nil
}

// DigestPendingOnReturnToDrafting digests pending supplements after a transition back to drafting.
func (e *GovernanceEngine) DigestPendingOnReturnToDrafting(ctx context.Context, doc *DocumentRecord, actorID int64, notify PendingSupplementNotify) {
	if e == nil || doc == nil || doc.CurrentState != StateDrafting {
		return
	}
	pending, err := e.DigestPendingSupplements(ctx, doc.DocID, actorID)
	if err != nil || len(pending) == 0 {
		return
	}
	if notify != nil {
		notify(ctx, doc, pending)
	}
}