package tools

import (
	"encoding/json"
	"strings"

	"gitea.d-ma.be/mathias/gitea-mcp/internal/registry"
)

// Tool implements registry.Tool.
type Tool = registry.Tool

func textOK(v any) (json.RawMessage, error) {
	return json.Marshal(v)
}

func parseArgs(raw json.RawMessage, dst any) error {
	if len(raw) == 0 {
		return json.Unmarshal([]byte("{}"), dst)
	}
	return json.Unmarshal(normalizeAliases(raw), dst)
}

// normalizeAliases maps the near-universal gitea/GitHub argument names onto the
// idiosyncratic ones these tools declare: `repo` -> `name`, `index` -> `number`.
// Every MCP caller (the claude.ai connector, LLMs primed on gitea's own API)
// reaches for `repo`/`index`; without this the unmatched fields zero-valued the
// upstream path segment and produced gitea's misleading /api/swagger 404 (#36).
// The alias key is left intact so a tool whose real field IS `index`
// (e.g. pr_merge) is unaffected.
func normalizeAliases(raw json.RawMessage) json.RawMessage {
	var m map[string]json.RawMessage
	if err := json.Unmarshal(raw, &m); err != nil {
		return raw // not a JSON object — leave untouched
	}
	changed := aliasInto(m, "name", "repo")
	changed = aliasInto(m, "number", "index") || changed
	if !changed {
		return raw
	}
	if patched, err := json.Marshal(m); err == nil {
		return patched
	}
	return raw
}

// aliasInto copies m[alias] into m[canonical] when canonical is absent or an
// empty/zero JSON value and alias carries a usable one. An explicit canonical
// value always wins. Returns true if it wrote canonical.
func aliasInto(m map[string]json.RawMessage, canonical, alias string) bool {
	av, ok := m[alias]
	if !ok || isEmptyJSON(av) {
		return false
	}
	if cv, ok := m[canonical]; ok && !isEmptyJSON(cv) {
		return false
	}
	m[canonical] = av
	return true
}

func isEmptyJSON(v json.RawMessage) bool {
	switch strings.TrimSpace(string(v)) {
	case "", `""`, "null", "0":
		return true
	default:
		return false
	}
}

// capLimit returns a sane page size: 0 or negative → def, > 50 → 50.
func capLimit(in, def int) int {
	if in <= 0 {
		return def
	}
	if in > 50 {
		return 50
	}
	return in
}