package dbml

import (
	"fmt"
	"regexp"
	"strings"

	"git.warky.dev/wdevs/relspecgo/pkg/models"
)

// directiveLineRegex matches a dialect directive line:
//
//	@postgres: partition by RANGE (created_at)
//	@postgres(id): identity always
//
// Group 1 is the namespace, group 2 the optional (column) target, group 3 the
// raw argument text (validated separately so error messages can be specific).
var directiveLineRegex = regexp.MustCompile(`^@([^():]*)(?:\(([^()]*)\))?\s*:(.*)$`)

// namespaceRegex is the grammar for a directive namespace.
var namespaceRegex = regexp.MustCompile(`^[a-z][a-z0-9_]*$`)

// parsedDirective is a directive line that has been parsed but not yet attached
// to a model object.
type parsedDirective struct {
	namespace string
	target    string // column name; "" when absent
	args      string
	line      int
}

// parseDirectiveLine parses a single "@namespace[(target)]: args" line.
func parseDirectiveLine(line string, lineNo int) (parsedDirective, error) {
	m := directiveLineRegex.FindStringSubmatch(line)
	if m == nil {
		return parsedDirective{}, fmt.Errorf(
			"dbml: line %d: malformed directive %q (expected \"@namespace: args\")", lineNo, line)
	}

	ns := strings.TrimSpace(m[1])
	target := strings.TrimSpace(m[2])
	args := strings.TrimSpace(m[3])

	if !namespaceRegex.MatchString(ns) {
		return parsedDirective{}, fmt.Errorf(
			"dbml: line %d: invalid directive namespace %q (must match [a-z][a-z0-9_]*)", lineNo, ns)
	}
	if args == "" {
		return parsedDirective{}, fmt.Errorf("dbml: line %d: directive @%s has no arguments", lineNo, ns)
	}
	if target != "" {
		target = stripQuotes(target)
	}

	return parsedDirective{namespace: ns, target: target, args: args, line: lineNo}, nil
}

// attachDirective resolves the target model object from the current parser state
// and stores the directive in its Metadata, enforcing location, duplicate and
// strict-mode rules.
func (r *Reader) attachDirective(
	pd parsedDirective,
	db *models.Database,
	table *models.Table,
	inTable, inIndexes bool,
	lastIndex *models.Index,
) error {
	strict := r.options != nil && r.options.StrictDirectives
	key := models.DirectiveKey(pd.args)

	var meta map[string]any
	var location string

	switch {
	case inIndexes:
		if pd.target != "" {
			return fmt.Errorf("dbml: line %d: directive target (%s) is not allowed inside an indexes block", pd.line, pd.target)
		}
		if lastIndex == nil {
			return fmt.Errorf("dbml: line %d: directive @%s must follow an index definition", pd.line, pd.namespace)
		}
		if lastIndex.Metadata == nil {
			lastIndex.Metadata = make(map[string]any)
		}
		meta = lastIndex.Metadata
		location = models.DirectiveLocationIndex

	case inTable && table != nil:
		if pd.target != "" {
			col, ok := table.Columns[pd.target]
			if !ok {
				return fmt.Errorf("dbml: line %d: directive target column %q not found in table %q", pd.line, pd.target, table.Name)
			}
			if col.Metadata == nil {
				col.Metadata = make(map[string]any)
			}
			meta = col.Metadata
			location = models.DirectiveLocationColumn
		} else {
			if table.Metadata == nil {
				table.Metadata = make(map[string]any)
			}
			meta = table.Metadata
			location = models.DirectiveLocationTable
		}

	default:
		if pd.target != "" {
			return fmt.Errorf("dbml: line %d: directive target (%s) is only valid inside a table", pd.line, pd.target)
		}
		if db.Metadata == nil {
			db.Metadata = make(map[string]any)
		}
		meta = db.Metadata
		location = models.DirectiveLocationDatabase
	}

	spec, documented := models.LookupDirectiveSpec(pd.namespace, key)

	if strict && !documented {
		return fmt.Errorf("dbml: line %d: unknown directive @%s: %s (strict mode)", pd.line, pd.namespace, key)
	}
	if documented && !models.DirectiveLocationAllowed(pd.namespace, key, location) {
		return fmt.Errorf("dbml: line %d: directive @%s: %s is not valid at %s level", pd.line, pd.namespace, key, location)
	}
	if documented && spec.Singleton && models.HasDirective(meta, pd.namespace, key) {
		return fmt.Errorf("dbml: line %d: duplicate @%s directive %q at %s level", pd.line, pd.namespace, key, location)
	}

	models.AddDirective(meta, models.Directive{
		Namespace: pd.namespace,
		Key:       key,
		Args:      pd.args,
		Line:      pd.line,
	})
	return nil
}