package storage

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"strconv"
	"strings"
	"time"

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

	"archivdms/internal/matching"
)

// ErrWorkflowNotFound is returned when a workflow lookup, update or delete does
// not match any row owned by the caller's tenant.
var ErrWorkflowNotFound = errors.New("storage: workflow not found or not owned by tenant")

// ErrDuplicateWorkflowName is returned when a tenant already has a workflow
// with the same name (UNIQUE(tenant_id, name)).
var ErrDuplicateWorkflowName = errors.New("storage: workflow with this name already exists for tenant")

// ErrInvalidConditionTree is returned when a supplied condition_tree is
// malformed or exceeds the MVP nesting-depth guardrail.
var ErrInvalidConditionTree = errors.New("storage: invalid workflow condition tree")

// ErrInvalidWorkflowAction is returned when a supplied workflow action has an
// unknown action_type or a malformed action_config for its type.
var ErrInvalidWorkflowAction = errors.New("storage: invalid workflow action")

// Supported workflow trigger types (mirrors the trigger_type CHECK).
const WorkflowTriggerOnUpload = "on_upload"

// Supported workflow action types (mirrors the action_type CHECK).
const (
	ActionAddTag                    = "add_tag"
	ActionSetDocType                = "set_doc_type"
	ActionSetCorrespondent          = "set_correspondent"
	ActionApplyClassificationTmpl   = "apply_classification_template"
	ActionSetCustomField            = "set_custom_field"
)

// Leaf fields supported in a condition tree (MVP).
const (
	FieldOCRText       = "ocr_text"
	FieldTitle         = "title"
	FieldDocType       = "doc_type"
	FieldCorrespondent = "correspondent"
	FieldSource        = "source"
)

// Boolean operators in a condition tree.
const (
	OpAnd = "and"
	OpOr  = "or"
)

// ConditionNode is one node of a workflow condition tree. It is either a
// boolean group (Op + Children set) or a leaf (Field + Algorithm + Pattern
// set). The two forms are mutually exclusive. Parsed/validated on write and
// stored both as the typed struct (validation) and raw JSONB (DB column).
type ConditionNode struct {
	// Group form.
	Op       string          `json:"op,omitempty"`
	Children []ConditionNode `json:"children,omitempty"`
	// Leaf form.
	Field         string `json:"field,omitempty"`
	Algorithm     string `json:"algorithm,omitempty"`
	Pattern       string `json:"pattern,omitempty"`
	CaseSensitive bool   `json:"case_sensitive,omitempty"`
}

// isGroup reports whether the node is a boolean group (has an op).
func (n ConditionNode) isGroup() bool {
	return n.Op != ""
}

// Workflow is a tenant-scoped automation rule evaluated at a trigger point
// (MVP: on_upload). A matched workflow runs its ordered actions against the
// document. Every evaluation is recorded in workflow_runs for GoBD
// traceability (document-scoped audit trail parallel to internal/audit).
type Workflow struct {
	ID            int64            `json:"id"`
	TenantID      int64            `json:"tenant_id"`
	Name          string           `json:"name"`
	Enabled       bool             `json:"enabled"`
	TriggerType   string           `json:"trigger_type"`
	ConditionTree ConditionNode    `json:"condition_tree"`
	Priority      int              `json:"priority"`
	CreatedBy     *int64           `json:"created_by,omitempty"`
	CreatedAt     time.Time        `json:"created_at"`
	UpdatedAt     time.Time        `json:"updated_at"`
	Actions       []WorkflowAction `json:"actions"`
}

// WorkflowAction is one ordered action of a workflow, with its type-specific
// configuration carried as raw JSON (validated on write).
type WorkflowAction struct {
	ID           int64           `json:"id"`
	WorkflowID   int64           `json:"workflow_id"`
	StepOrder    int             `json:"step_order"`
	ActionType   string          `json:"action_type"`
	ActionConfig json.RawMessage `json:"action_config"`
}

// WorkflowActionInput is one supplied action in a bulk PUT (step_order is the
// slice index, assigned by SetWorkflowActions).
type WorkflowActionInput struct {
	ActionType   string          `json:"action_type"`
	ActionConfig json.RawMessage `json:"action_config"`
}

// CreateWorkflowRequest holds create parameters for a workflow.
type CreateWorkflowRequest struct {
	Name          string
	Enabled       bool
	TriggerType   string
	ConditionTree json.RawMessage
	Priority      int
	CreatedBy     *int64
}

// UpdateWorkflowRequest holds update parameters for a workflow.
type UpdateWorkflowRequest struct {
	Name          string
	Enabled       bool
	TriggerType   string
	ConditionTree json.RawMessage
	Priority      int
}

// WorkflowRun is one recorded evaluation of a workflow against a document.
type WorkflowRun struct {
	ID             int64           `json:"id"`
	WorkflowID     int64           `json:"workflow_id"`
	TenantID       int64           `json:"tenant_id"`
	DocumentID     *int64          `json:"document_id,omitempty"`
	TriggeredAt    time.Time       `json:"triggered_at"`
	Matched        bool            `json:"matched"`
	ActionsApplied json.RawMessage `json:"actions_applied,omitempty"`
	Error          string          `json:"error,omitempty"`
}

// WorkflowTestResult is the dry-run outcome of TestWorkflow: whether the tree
// matched, the per-leaf evaluation, and which actions WOULD run (never
// executed).
type WorkflowTestResult struct {
	WorkflowID   int64             `json:"workflow_id"`
	Matched      bool              `json:"matched"`
	Leaves       []LeafEvalResult  `json:"leaves"`
	ActionsToRun []WorkflowAction  `json:"actions_to_run"`
}

// LeafEvalResult records the evaluation of a single leaf condition.
type LeafEvalResult struct {
	Field     string `json:"field"`
	Algorithm string `json:"algorithm"`
	Pattern   string `json:"pattern"`
	Value     string `json:"value"`
	Matched   bool   `json:"matched"`
}

// initWorkflowsSchema creates the workflows / workflow_actions / workflow_runs
// tables. Idempotent, called from (*Store).initSchema AFTER
// initClassificationTemplatesSchema (a workflow action can reference a
// classification template). Documented (not executed) in
// migrations/012_workflows.sql.
func (s *Store) initWorkflowsSchema(ctx context.Context) error {
	_, err := s.db.Exec(ctx, `
		CREATE TABLE IF NOT EXISTS workflows (
			id              BIGSERIAL PRIMARY KEY,
			tenant_id       BIGINT NOT NULL,
			name            TEXT NOT NULL,
			enabled         BOOLEAN NOT NULL DEFAULT true,
			trigger_type    TEXT NOT NULL CHECK (trigger_type IN ('on_upload')),
			condition_tree  JSONB NOT NULL,
			priority        INT NOT NULL DEFAULT 100,
			created_by      BIGINT,
			created_at      TIMESTAMPTZ NOT NULL DEFAULT now(),
			updated_at      TIMESTAMPTZ NOT NULL DEFAULT now(),
			UNIQUE(tenant_id, name)
		);
		CREATE INDEX IF NOT EXISTS idx_workflows_tenant ON workflows(tenant_id);

		CREATE TABLE IF NOT EXISTS workflow_actions (
			id            BIGSERIAL PRIMARY KEY,
			workflow_id   BIGINT NOT NULL REFERENCES workflows(id) ON DELETE CASCADE,
			step_order    INT NOT NULL,
			action_type   TEXT NOT NULL CHECK (action_type IN
				('add_tag','set_doc_type','set_correspondent','apply_classification_template','set_custom_field')),
			action_config JSONB NOT NULL DEFAULT '{}'
		);
		CREATE INDEX IF NOT EXISTS idx_workflow_actions_workflow ON workflow_actions(workflow_id, step_order);

		CREATE TABLE IF NOT EXISTS workflow_runs (
			id              BIGSERIAL PRIMARY KEY,
			workflow_id     BIGINT NOT NULL REFERENCES workflows(id) ON DELETE CASCADE,
			tenant_id       BIGINT NOT NULL,
			document_id     BIGINT,
			triggered_at    TIMESTAMPTZ NOT NULL DEFAULT now(),
			matched         BOOLEAN NOT NULL,
			actions_applied JSONB,
			error           TEXT
		);
		CREATE INDEX IF NOT EXISTS idx_workflow_runs_workflow ON workflow_runs(workflow_id);
		CREATE INDEX IF NOT EXISTS idx_workflow_runs_document ON workflow_runs(document_id);
	`)
	if err != nil {
		return fmt.Errorf("storage: create workflows tables: %w", err)
	}
	return nil
}

// --- condition tree validation --------------------------------------------

// maxConditionDepth is the MVP nesting guardrail: a top-level op plus one level
// of nested op groups (depth 2). Deeper trees are rejected — an MVP guardrail,
// not a hard architectural limit.
const maxConditionDepth = 2

var validConditionFields = map[string]bool{
	FieldOCRText: true, FieldTitle: true, FieldDocType: true,
	FieldCorrespondent: true, FieldSource: true,
}

var validConditionAlgorithms = map[string]bool{
	matching.AlgorithmAny: true, matching.AlgorithmAll: true,
	matching.AlgorithmExact: true, matching.AlgorithmRegex: true,
	matching.AlgorithmFuzzy: true,
}

// parseConditionTree unmarshals and validates a raw condition tree into the
// typed ConditionNode, enforcing the depth guardrail and leaf/group shape.
func parseConditionTree(raw json.RawMessage) (ConditionNode, error) {
	if len(raw) == 0 {
		return ConditionNode{}, fmt.Errorf("%w: empty", ErrInvalidConditionTree)
	}
	var root ConditionNode
	if err := json.Unmarshal(raw, &root); err != nil {
		return ConditionNode{}, fmt.Errorf("%w: %v", ErrInvalidConditionTree, err)
	}
	if err := validateConditionNode(root, 1); err != nil {
		return ConditionNode{}, err
	}
	return root, nil
}

// validateConditionNode recursively validates a node. depth starts at 1 for
// the root; a group's children are at depth+1 and may not exceed
// maxConditionDepth.
func validateConditionNode(n ConditionNode, depth int) error {
	if n.isGroup() {
		if n.Op != OpAnd && n.Op != OpOr {
			return fmt.Errorf("%w: unknown op %q", ErrInvalidConditionTree, n.Op)
		}
		if n.Field != "" || n.Algorithm != "" || n.Pattern != "" {
			return fmt.Errorf("%w: node has both group op and leaf fields", ErrInvalidConditionTree)
		}
		if len(n.Children) == 0 {
			return fmt.Errorf("%w: group %q has no children", ErrInvalidConditionTree, n.Op)
		}
		if depth >= maxConditionDepth {
			// Children of this group would exceed the guardrail unless they are
			// all leaves. Enforce: at depth == maxConditionDepth no child may be
			// a group.
			for _, c := range n.Children {
				if c.isGroup() {
					return fmt.Errorf("%w: nesting deeper than %d levels", ErrInvalidConditionTree, maxConditionDepth)
				}
			}
		}
		for _, c := range n.Children {
			if err := validateConditionNode(c, depth+1); err != nil {
				return err
			}
		}
		return nil
	}
	// Leaf.
	if !validConditionFields[n.Field] {
		return fmt.Errorf("%w: unknown field %q", ErrInvalidConditionTree, n.Field)
	}
	if !validConditionAlgorithms[n.Algorithm] {
		return fmt.Errorf("%w: unknown algorithm %q", ErrInvalidConditionTree, n.Algorithm)
	}
	if strings.TrimSpace(n.Pattern) == "" {
		return fmt.Errorf("%w: leaf field %q has empty pattern", ErrInvalidConditionTree, n.Field)
	}
	return nil
}

// validateActionConfig validates one action's type and its JSON config shape.
func validateActionConfig(actionType string, cfg json.RawMessage) error {
	switch actionType {
	case ActionAddTag:
		var c struct {
			TagID int64 `json:"tag_id"`
		}
		if err := json.Unmarshal(nonNilJSON(cfg), &c); err != nil || c.TagID == 0 {
			return fmt.Errorf("%w: %s requires tag_id", ErrInvalidWorkflowAction, actionType)
		}
	case ActionSetDocType:
		var c struct {
			DocTypeID int64 `json:"doc_type_id"`
		}
		if err := json.Unmarshal(nonNilJSON(cfg), &c); err != nil || c.DocTypeID == 0 {
			return fmt.Errorf("%w: %s requires doc_type_id", ErrInvalidWorkflowAction, actionType)
		}
	case ActionSetCorrespondent:
		var c struct {
			CorrespondentID int64 `json:"correspondent_id"`
		}
		if err := json.Unmarshal(nonNilJSON(cfg), &c); err != nil || c.CorrespondentID == 0 {
			return fmt.Errorf("%w: %s requires correspondent_id", ErrInvalidWorkflowAction, actionType)
		}
	case ActionApplyClassificationTmpl:
		var c struct {
			TemplateID int64 `json:"template_id"`
		}
		if err := json.Unmarshal(nonNilJSON(cfg), &c); err != nil || c.TemplateID == 0 {
			return fmt.Errorf("%w: %s requires template_id", ErrInvalidWorkflowAction, actionType)
		}
	case ActionSetCustomField:
		var c struct {
			FieldID int64 `json:"field_id"`
		}
		if err := json.Unmarshal(nonNilJSON(cfg), &c); err != nil || c.FieldID == 0 {
			return fmt.Errorf("%w: %s requires field_id", ErrInvalidWorkflowAction, actionType)
		}
	default:
		return fmt.Errorf("%w: unknown action_type %q", ErrInvalidWorkflowAction, actionType)
	}
	return nil
}

// nonNilJSON returns raw, or an empty JSON object when raw is nil/empty, so
// json.Unmarshal does not fail on a missing action_config.
func nonNilJSON(raw json.RawMessage) json.RawMessage {
	if len(raw) == 0 {
		return json.RawMessage(`{}`)
	}
	return raw
}

// --- CRUD ------------------------------------------------------------------

const workflowCols = `id, tenant_id, name, enabled, trigger_type, condition_tree, priority, created_by, created_at, updated_at`

// scanWorkflow scans a workflow row (without actions) and parses its raw
// condition_tree JSONB into the typed struct.
func scanWorkflow(row interface {
	Scan(dest ...any) error
}) (*Workflow, error) {
	var w Workflow
	var rawTree []byte
	if err := row.Scan(&w.ID, &w.TenantID, &w.Name, &w.Enabled, &w.TriggerType,
		&rawTree, &w.Priority, &w.CreatedBy, &w.CreatedAt, &w.UpdatedAt); err != nil {
		return nil, err
	}
	// Best-effort parse: a stored tree was validated on write, so a parse error
	// here is a data-integrity anomaly — surface it rather than silently drop.
	if len(rawTree) > 0 {
		if err := json.Unmarshal(rawTree, &w.ConditionTree); err != nil {
			return nil, fmt.Errorf("storage: unmarshal stored condition_tree: %w", err)
		}
	}
	w.Actions = make([]WorkflowAction, 0)
	return &w, nil
}

// CreateWorkflow inserts a new workflow (without actions — those are set via
// SetWorkflowActions). It validates the condition tree depth/shape and stores
// both the validated tree (as raw JSONB) and the typed struct on the return.
func (s *Store) CreateWorkflow(ctx context.Context, tenantID int64, req CreateWorkflowRequest) (*Workflow, error) {
	if req.TriggerType == "" {
		req.TriggerType = WorkflowTriggerOnUpload
	}
	if req.TriggerType != WorkflowTriggerOnUpload {
		return nil, fmt.Errorf("%w: unsupported trigger_type %q", ErrInvalidConditionTree, req.TriggerType)
	}
	tree, err := parseConditionTree(req.ConditionTree)
	if err != nil {
		return nil, err
	}
	row := s.db.QueryRow(ctx, `
		INSERT INTO workflows (tenant_id, name, enabled, trigger_type, condition_tree, priority, created_by)
		VALUES ($1, $2, $3, $4, $5, $6, $7)
		RETURNING `+workflowCols,
		tenantID, req.Name, req.Enabled, req.TriggerType, []byte(req.ConditionTree), req.Priority, req.CreatedBy)
	w, err := scanWorkflow(row)
	if err != nil {
		var pgErr *pgconn.PgError
		if errors.As(err, &pgErr) && pgErr.Code == "23505" {
			return nil, ErrDuplicateWorkflowName
		}
		return nil, fmt.Errorf("storage: create workflow: %w", err)
	}
	w.ConditionTree = tree
	return w, nil
}

// ListWorkflows returns all workflows for a tenant (without actions), ordered
// by priority then name. Returns a non-nil (possibly empty) slice.
func (s *Store) ListWorkflows(ctx context.Context, tenantID int64) ([]Workflow, error) {
	rows, err := s.db.Query(ctx, `SELECT `+workflowCols+`
		FROM workflows WHERE tenant_id = $1 ORDER BY priority ASC, name ASC`, tenantID)
	if err != nil {
		return nil, fmt.Errorf("storage: list workflows: %w", err)
	}
	defer rows.Close()

	out := make([]Workflow, 0)
	for rows.Next() {
		w, err := scanWorkflow(rows)
		if err != nil {
			return nil, fmt.Errorf("storage: scan workflow: %w", err)
		}
		out = append(out, *w)
	}
	return out, rows.Err()
}

// GetWorkflow returns one workflow resolved with its ordered actions, scoped to
// tenant ownership.
func (s *Store) GetWorkflow(ctx context.Context, id, tenantID int64) (*Workflow, error) {
	row := s.db.QueryRow(ctx, `SELECT `+workflowCols+`
		FROM workflows WHERE id = $1 AND tenant_id = $2`, id, tenantID)
	w, err := scanWorkflow(row)
	if err != nil {
		if errors.Is(err, pgx.ErrNoRows) {
			return nil, ErrWorkflowNotFound
		}
		return nil, fmt.Errorf("storage: get workflow: %w", err)
	}
	actions, err := s.listWorkflowActions(ctx, id)
	if err != nil {
		return nil, err
	}
	w.Actions = actions
	return w, nil
}

// listWorkflowActions returns the actions of a workflow ordered by step_order.
func (s *Store) listWorkflowActions(ctx context.Context, workflowID int64) ([]WorkflowAction, error) {
	rows, err := s.db.Query(ctx, `
		SELECT id, workflow_id, step_order, action_type, action_config
		FROM workflow_actions WHERE workflow_id = $1 ORDER BY step_order ASC`, workflowID)
	if err != nil {
		return nil, fmt.Errorf("storage: list workflow actions: %w", err)
	}
	defer rows.Close()

	out := make([]WorkflowAction, 0)
	for rows.Next() {
		var a WorkflowAction
		var cfg []byte
		if err := rows.Scan(&a.ID, &a.WorkflowID, &a.StepOrder, &a.ActionType, &cfg); err != nil {
			return nil, fmt.Errorf("storage: scan workflow action: %w", err)
		}
		a.ActionConfig = json.RawMessage(cfg)
		out = append(out, a)
	}
	return out, rows.Err()
}

// UpdateWorkflow updates a workflow's core attributes (not its actions), scoped
// to tenant ownership. Re-validates the condition tree.
func (s *Store) UpdateWorkflow(ctx context.Context, id, tenantID int64, req UpdateWorkflowRequest) error {
	if req.TriggerType == "" {
		req.TriggerType = WorkflowTriggerOnUpload
	}
	if req.TriggerType != WorkflowTriggerOnUpload {
		return fmt.Errorf("%w: unsupported trigger_type %q", ErrInvalidConditionTree, req.TriggerType)
	}
	if _, err := parseConditionTree(req.ConditionTree); err != nil {
		return err
	}
	tag, err := s.db.Exec(ctx, `
		UPDATE workflows
		SET name = $1, enabled = $2, trigger_type = $3, condition_tree = $4, priority = $5, updated_at = now()
		WHERE id = $6 AND tenant_id = $7
	`, req.Name, req.Enabled, req.TriggerType, []byte(req.ConditionTree), req.Priority, id, tenantID)
	if err != nil {
		var pgErr *pgconn.PgError
		if errors.As(err, &pgErr) && pgErr.Code == "23505" {
			return ErrDuplicateWorkflowName
		}
		return fmt.Errorf("storage: update workflow: %w", err)
	}
	if tag.RowsAffected() == 0 {
		return ErrWorkflowNotFound
	}
	return nil
}

// DeleteWorkflow deletes a workflow (cascades to its actions / runs), scoped to
// tenant ownership.
func (s *Store) DeleteWorkflow(ctx context.Context, id, tenantID int64) error {
	tag, err := s.db.Exec(ctx, `DELETE FROM workflows WHERE id = $1 AND tenant_id = $2`, id, tenantID)
	if err != nil {
		return fmt.Errorf("storage: delete workflow: %w", err)
	}
	if tag.RowsAffected() == 0 {
		return ErrWorkflowNotFound
	}
	return nil
}

// workflowOwned returns true if the workflow belongs to the tenant.
func (s *Store) workflowOwned(ctx context.Context, workflowID, tenantID int64) (bool, error) {
	var ok bool
	err := s.db.QueryRow(ctx, `SELECT EXISTS(SELECT 1 FROM workflows WHERE id = $1 AND tenant_id = $2)`, workflowID, tenantID).Scan(&ok)
	if err != nil {
		return false, fmt.Errorf("storage: check workflow ownership: %w", err)
	}
	return ok, nil
}

// SetWorkflowActions replaces the complete ordered set of actions on a workflow
// (bulk PUT). step_order is the slice index. Each action's config is validated
// against its type. Delete-all + insert in one transaction (mirrors
// SetTemplateFieldDefaults). Scoped to tenant ownership of the workflow.
func (s *Store) SetWorkflowActions(ctx context.Context, workflowID, tenantID int64, actions []WorkflowActionInput) error {
	owns, err := s.workflowOwned(ctx, workflowID, tenantID)
	if err != nil {
		return err
	}
	if !owns {
		return ErrWorkflowNotFound
	}
	for _, a := range actions {
		if err := validateActionConfig(a.ActionType, a.ActionConfig); err != nil {
			return err
		}
	}

	tx, err := s.db.Begin(ctx)
	if err != nil {
		return fmt.Errorf("storage: begin set workflow actions: %w", err)
	}
	defer tx.Rollback(ctx)

	if _, err := tx.Exec(ctx, `DELETE FROM workflow_actions WHERE workflow_id = $1`, workflowID); err != nil {
		return fmt.Errorf("storage: clear workflow actions: %w", err)
	}
	for i, a := range actions {
		if _, err := tx.Exec(ctx, `
			INSERT INTO workflow_actions (workflow_id, step_order, action_type, action_config)
			VALUES ($1, $2, $3, $4)
		`, workflowID, i, a.ActionType, []byte(nonNilJSON(a.ActionConfig))); err != nil {
			return fmt.Errorf("storage: insert workflow action: %w", err)
		}
	}
	if err := tx.Commit(ctx); err != nil {
		return fmt.Errorf("storage: commit set workflow actions: %w", err)
	}
	return nil
}

// --- evaluation ------------------------------------------------------------

// resolveLeafValue returns the document's value for a leaf field. For doc_type
// and correspondent it resolves the taxonomy entity's name when the *_id is
// set, falling back to the deprecated free-text column.
func (s *Store) resolveLeafValue(ctx context.Context, field string, doc *Document) (string, error) {
	switch field {
	case FieldOCRText:
		return doc.OCRText, nil
	case FieldTitle:
		return doc.Title, nil
	case FieldSource:
		return doc.Source, nil
	case FieldDocType:
		if doc.DocTypeID != nil {
			name, err := s.taxonomyName(ctx, "document_types", *doc.DocTypeID, doc.TenantID)
			if err != nil {
				return "", err
			}
			if name != "" {
				return name, nil
			}
		}
		return doc.DocType, nil
	case FieldCorrespondent:
		if doc.CorrespondentID != nil {
			name, err := s.taxonomyName(ctx, "correspondents", *doc.CorrespondentID, doc.TenantID)
			if err != nil {
				return "", err
			}
			if name != "" {
				return name, nil
			}
		}
		return doc.Correspondent, nil
	default:
		return "", nil
	}
}

// taxonomyName resolves a taxonomy entity's name by id, scoped to tenant.
// Returns "" (no error) when no row matches.
func (s *Store) taxonomyName(ctx context.Context, kind string, id, tenantID int64) (string, error) {
	table, err := taxonomyTable(kind)
	if err != nil {
		return "", err
	}
	var name string
	err = s.db.QueryRow(ctx, fmt.Sprintf(`SELECT name FROM %s WHERE id = $1 AND tenant_id = $2`, table), id, tenantID).Scan(&name)
	if err != nil {
		if errors.Is(err, pgx.ErrNoRows) {
			return "", nil
		}
		return "", fmt.Errorf("storage: resolve %s name: %w", kind, err)
	}
	return name, nil
}

// evalNode recursively evaluates a condition node against a document, appending
// per-leaf results to *leaves (nil to skip collection). When leaves is non-nil
// (test endpoint) all children are walked so every leaf is reported; the group
// result itself is still computed honestly.
func (s *Store) evalNode(ctx context.Context, n ConditionNode, doc *Document, leaves *[]LeafEvalResult) (bool, error) {
	if n.isGroup() {
		if n.Op == OpAnd {
			result := true
			for _, c := range n.Children {
				ok, err := s.evalNode(ctx, c, doc, leaves)
				if err != nil {
					return false, err
				}
				if !ok {
					result = false
					if leaves == nil {
						return false, nil // short-circuit when not collecting
					}
				}
			}
			return result, nil
		}
		// OR.
		result := false
		for _, c := range n.Children {
			ok, err := s.evalNode(ctx, c, doc, leaves)
			if err != nil {
				return false, err
			}
			if ok {
				result = true
				if leaves == nil {
					return true, nil // short-circuit when not collecting
				}
			}
		}
		return result, nil
	}
	// Leaf.
	value, err := s.resolveLeafValue(ctx, n.Field, doc)
	if err != nil {
		return false, err
	}
	matched := matching.Match(n.Algorithm, n.Pattern, n.CaseSensitive, value)
	if leaves != nil {
		*leaves = append(*leaves, LeafEvalResult{
			Field: n.Field, Algorithm: n.Algorithm, Pattern: n.Pattern,
			Value: value, Matched: matched,
		})
	}
	return matched, nil
}

// EvaluateWorkflow walks the workflow's condition tree against a document and
// reports whether it matched. Leaf conditions reuse the matching-engine
// algorithms (internal/matching) against the resolved field value.
func (s *Store) EvaluateWorkflow(ctx context.Context, workflow *Workflow, doc *Document) (bool, error) {
	return s.evalNode(ctx, workflow.ConditionTree, doc, nil)
}

// --- execution -------------------------------------------------------------

// RunWorkflowsForDocument loads all enabled workflows of the tenant with the
// given trigger type (ordered by priority ASC), evaluates each and runs the
// ordered actions of matched ones. Every workflow evaluated produces a
// workflow_runs row (matched true/false, actions_applied summary, error). A
// failed action never aborts the document upload — it is recorded and the loop
// continues (mirrors the "never fail the upload" philosophy of the OCR /
// auto-assign steps in storeUploadedFile).
func (s *Store) RunWorkflowsForDocument(ctx context.Context, tenantID int64, doc *Document, triggerType string) error {
	rows, err := s.db.Query(ctx, `SELECT `+workflowCols+`
		FROM workflows WHERE tenant_id = $1 AND enabled = true AND trigger_type = $2
		ORDER BY priority ASC, id ASC`, tenantID, triggerType)
	if err != nil {
		return fmt.Errorf("storage: load workflows for document: %w", err)
	}
	workflows := make([]Workflow, 0)
	for rows.Next() {
		w, err := scanWorkflow(rows)
		if err != nil {
			rows.Close()
			return fmt.Errorf("storage: scan workflow for document: %w", err)
		}
		workflows = append(workflows, *w)
	}
	rows.Close()
	if err := rows.Err(); err != nil {
		return fmt.Errorf("storage: iterate workflows for document: %w", err)
	}

	for i := range workflows {
		w := &workflows[i]
		matched, err := s.EvaluateWorkflow(ctx, w, doc)
		if err != nil {
			s.recordWorkflowRun(ctx, w.ID, tenantID, &doc.ID, false, nil, err.Error())
			continue
		}
		if !matched {
			s.recordWorkflowRun(ctx, w.ID, tenantID, &doc.ID, false, nil, "")
			continue
		}
		actions, err := s.listWorkflowActions(ctx, w.ID)
		if err != nil {
			s.recordWorkflowRun(ctx, w.ID, tenantID, &doc.ID, true, nil, err.Error())
			continue
		}
		applied, runErr := s.executeWorkflowActions(ctx, tenantID, doc, actions)
		var errStr string
		if runErr != nil {
			errStr = runErr.Error()
		}
		s.recordWorkflowRun(ctx, w.ID, tenantID, &doc.ID, true, applied, errStr)
	}
	return nil
}

// executeWorkflowActions runs a workflow's ordered actions against a document.
// A failed action is recorded in the returned summary and as the returned
// error (first failure) but does not stop subsequent actions — best-effort,
// each action's outcome is captured for the workflow_runs audit trail.
func (s *Store) executeWorkflowActions(ctx context.Context, tenantID int64, doc *Document, actions []WorkflowAction) (json.RawMessage, error) {
	type actionResult struct {
		StepOrder  int    `json:"step_order"`
		ActionType string `json:"action_type"`
		OK         bool   `json:"ok"`
		Detail     string `json:"detail,omitempty"`
	}
	results := make([]actionResult, 0, len(actions))
	var firstErr error

	for _, a := range actions {
		res := actionResult{StepOrder: a.StepOrder, ActionType: a.ActionType}
		if err := s.executeWorkflowAction(ctx, tenantID, doc, a); err != nil {
			res.OK = false
			res.Detail = err.Error()
			if firstErr == nil {
				firstErr = err
			}
		} else {
			res.OK = true
		}
		results = append(results, res)
	}
	summary, err := json.Marshal(results)
	if err != nil {
		return nil, firstErr
	}
	return json.RawMessage(summary), firstErr
}

// executeWorkflowAction runs one workflow action against a document.
func (s *Store) executeWorkflowAction(ctx context.Context, tenantID int64, doc *Document, a WorkflowAction) error {
	switch a.ActionType {
	case ActionAddTag:
		var c struct {
			TagID int64 `json:"tag_id"`
		}
		if err := json.Unmarshal(nonNilJSON(a.ActionConfig), &c); err != nil {
			return fmt.Errorf("add_tag config: %w", err)
		}
		// Ownership: only attach a tag that belongs to the tenant.
		var ok bool
		if err := s.db.QueryRow(ctx, `SELECT EXISTS(SELECT 1 FROM tags WHERE id = $1 AND tenant_id = $2)`, c.TagID, tenantID).Scan(&ok); err != nil {
			return fmt.Errorf("add_tag ownership check: %w", err)
		}
		if !ok {
			return fmt.Errorf("%w: tag_id %d", ErrTaxonomyNotFound, c.TagID)
		}
		return s.AttachTag(ctx, doc.ID, c.TagID)
	case ActionSetDocType:
		var c struct {
			DocTypeID int64 `json:"doc_type_id"`
		}
		if err := json.Unmarshal(nonNilJSON(a.ActionConfig), &c); err != nil {
			return fmt.Errorf("set_doc_type config: %w", err)
		}
		var ok bool
		if err := s.db.QueryRow(ctx, `SELECT EXISTS(SELECT 1 FROM document_types WHERE id = $1 AND tenant_id = $2)`, c.DocTypeID, tenantID).Scan(&ok); err != nil {
			return fmt.Errorf("set_doc_type ownership check: %w", err)
		}
		if !ok {
			return fmt.Errorf("%w: doc_type_id %d", ErrTaxonomyNotFound, c.DocTypeID)
		}
		if err := s.SetDocumentDocType(ctx, doc.ID, tenantID, c.DocTypeID); err != nil {
			return err
		}
		doc.DocTypeID = &c.DocTypeID
		return nil
	case ActionSetCorrespondent:
		var c struct {
			CorrespondentID int64 `json:"correspondent_id"`
		}
		if err := json.Unmarshal(nonNilJSON(a.ActionConfig), &c); err != nil {
			return fmt.Errorf("set_correspondent config: %w", err)
		}
		var ok bool
		if err := s.db.QueryRow(ctx, `SELECT EXISTS(SELECT 1 FROM correspondents WHERE id = $1 AND tenant_id = $2)`, c.CorrespondentID, tenantID).Scan(&ok); err != nil {
			return fmt.Errorf("set_correspondent ownership check: %w", err)
		}
		if !ok {
			return fmt.Errorf("%w: correspondent_id %d", ErrTaxonomyNotFound, c.CorrespondentID)
		}
		if err := s.SetDocumentCorrespondent(ctx, doc.ID, tenantID, c.CorrespondentID); err != nil {
			return err
		}
		doc.CorrespondentID = &c.CorrespondentID
		return nil
	case ActionApplyClassificationTmpl:
		var c struct {
			TemplateID int64 `json:"template_id"`
			Overwrite  bool  `json:"overwrite"`
		}
		if err := json.Unmarshal(nonNilJSON(a.ActionConfig), &c); err != nil {
			return fmt.Errorf("apply_classification_template config: %w", err)
		}
		_, err := s.ApplyTemplate(ctx, doc.ID, c.TemplateID, tenantID, c.Overwrite)
		return err
	case ActionSetCustomField:
		return s.applyWorkflowCustomField(ctx, tenantID, doc, a.ActionConfig)
	default:
		return fmt.Errorf("%w: unknown action_type %q", ErrInvalidWorkflowAction, a.ActionType)
	}
}

// applyWorkflowCustomField sets a single custom-field value on the document,
// merging with the document's existing values (SetDocumentFieldValues is
// full-replace, so overlay the one field over the current set) and validating
// the value against the field type.
func (s *Store) applyWorkflowCustomField(ctx context.Context, tenantID int64, doc *Document, cfg json.RawMessage) error {
	var c struct {
		FieldID     int64    `json:"field_id"`
		Value       *string  `json:"value"`
		ValueText   *string  `json:"value_text"`
		ValueNumber *float64 `json:"value_number"`
		ValueDate   *string  `json:"value_date"`
		ValueBool   *bool    `json:"value_bool"`
	}
	if err := json.Unmarshal(nonNilJSON(cfg), &c); err != nil {
		return fmt.Errorf("set_custom_field config: %w", err)
	}
	if c.FieldID == 0 {
		return fmt.Errorf("%w: set_custom_field requires field_id", ErrInvalidWorkflowAction)
	}

	// Resolve the field type so a bare "value" string is routed to the correct
	// typed column.
	defs, err := s.ListCustomFieldDefs(ctx, tenantID)
	if err != nil {
		return err
	}
	var def *CustomFieldDef
	for i := range defs {
		if defs[i].ID == c.FieldID {
			def = &defs[i]
			break
		}
	}
	if def == nil {
		return fmt.Errorf("%w: field_id %d", ErrCustomFieldNotFound, c.FieldID)
	}

	newInput := DocumentFieldValueInput{FieldID: c.FieldID}
	// Explicit typed columns take precedence; otherwise route the bare "value".
	switch {
	case c.ValueText != nil || c.ValueNumber != nil || c.ValueDate != nil || c.ValueBool != nil:
		newInput.ValueText = c.ValueText
		newInput.ValueNumber = c.ValueNumber
		newInput.ValueDate = c.ValueDate
		newInput.ValueBool = c.ValueBool
	case c.Value != nil:
		switch def.FieldType {
		case "number", "monetary":
			f, perr := strconv.ParseFloat(*c.Value, 64)
			if perr != nil {
				return fmt.Errorf("set_custom_field: value %q not a number for field %q", *c.Value, def.Name)
			}
			newInput.ValueNumber = &f
		case "boolean":
			b, perr := strconv.ParseBool(*c.Value)
			if perr != nil {
				return fmt.Errorf("set_custom_field: value %q not a boolean for field %q", *c.Value, def.Name)
			}
			newInput.ValueBool = &b
		case "date":
			newInput.ValueDate = c.Value
		default:
			newInput.ValueText = c.Value
		}
	}

	// Merge with existing values (full-replace semantics of the setter).
	existing, err := s.ListDocumentFieldValues(ctx, doc.ID, tenantID)
	if err != nil {
		return err
	}
	inputs := make([]DocumentFieldValueInput, 0, len(existing)+1)
	replaced := false
	for _, v := range existing {
		if v.FieldID == c.FieldID {
			inputs = append(inputs, newInput)
			replaced = true
			continue
		}
		inputs = append(inputs, existingValueToInput(v))
	}
	if !replaced {
		inputs = append(inputs, newInput)
	}
	if _, err := s.SetDocumentFieldValues(ctx, doc.ID, tenantID, inputs); err != nil {
		return err
	}
	return nil
}

// recordWorkflowRun inserts a workflow_runs audit row. Best-effort: a failure
// to record is logged via the returned error being ignored by the caller
// (the run's effects are already applied). errStr is stored as NULL when empty.
func (s *Store) recordWorkflowRun(ctx context.Context, workflowID, tenantID int64, documentID *int64, matched bool, actionsApplied json.RawMessage, errStr string) {
	var applied []byte
	if len(actionsApplied) > 0 {
		applied = []byte(actionsApplied)
	}
	_, _ = s.db.Exec(ctx, `
		INSERT INTO workflow_runs (workflow_id, tenant_id, document_id, matched, actions_applied, error)
		VALUES ($1, $2, $3, $4, $5, $6)
	`, workflowID, tenantID, documentID, matched, applied, nullIfEmpty(errStr))
}

// ListWorkflowRuns returns the recorded runs of a workflow (most recent first),
// scoped to tenant ownership of the workflow. Returns a non-nil slice.
func (s *Store) ListWorkflowRuns(ctx context.Context, workflowID, tenantID int64, limit int) ([]WorkflowRun, error) {
	owns, err := s.workflowOwned(ctx, workflowID, tenantID)
	if err != nil {
		return nil, err
	}
	if !owns {
		return nil, ErrWorkflowNotFound
	}
	if limit <= 0 || limit > 500 {
		limit = 100
	}
	rows, err := s.db.Query(ctx, `
		SELECT id, workflow_id, tenant_id, document_id, triggered_at, matched, actions_applied, COALESCE(error, '')
		FROM workflow_runs WHERE workflow_id = $1 AND tenant_id = $2
		ORDER BY triggered_at DESC, id DESC LIMIT $3`, workflowID, tenantID, limit)
	if err != nil {
		return nil, fmt.Errorf("storage: list workflow runs: %w", err)
	}
	defer rows.Close()

	out := make([]WorkflowRun, 0)
	for rows.Next() {
		var run WorkflowRun
		var applied []byte
		if err := rows.Scan(&run.ID, &run.WorkflowID, &run.TenantID, &run.DocumentID,
			&run.TriggeredAt, &run.Matched, &applied, &run.Error); err != nil {
			return nil, fmt.Errorf("storage: scan workflow run: %w", err)
		}
		if len(applied) > 0 {
			run.ActionsApplied = json.RawMessage(applied)
		}
		out = append(out, run)
	}
	return out, rows.Err()
}

// TestWorkflow performs a pure dry-run of a workflow: it evaluates the
// condition tree against either an existing document (documentID set) or a
// synthetic in-memory document built from rawText (documentID nil), reporting
// which leaves matched and which actions WOULD run — never executing them.
func (s *Store) TestWorkflow(ctx context.Context, workflowID, tenantID int64, documentID *int64, rawText string) (*WorkflowTestResult, error) {
	w, err := s.GetWorkflow(ctx, workflowID, tenantID)
	if err != nil {
		return nil, err
	}

	var doc *Document
	if documentID != nil {
		doc, err = s.GetDocument(ctx, *documentID, tenantID)
		if err != nil {
			if errors.Is(err, pgx.ErrNoRows) {
				return nil, ErrDocumentNotFound
			}
			return nil, err
		}
	} else {
		// Synthetic document: rawText feeds both ocr_text and title so text
		// leaves can be exercised without a real upload.
		doc = &Document{TenantID: tenantID, Title: rawText, OCRText: rawText, Source: "test"}
	}

	leaves := make([]LeafEvalResult, 0)
	matched, err := s.evalNode(ctx, w.ConditionTree, doc, &leaves)
	if err != nil {
		return nil, err
	}

	res := &WorkflowTestResult{
		WorkflowID:   workflowID,
		Matched:      matched,
		Leaves:       leaves,
		ActionsToRun: make([]WorkflowAction, 0),
	}
	if matched {
		res.ActionsToRun = w.Actions
	}
	return res, nil
}