// mesh_convert.go implements meshgen.ConverterProvider against the
// mediautils shim's POST /v1/convert_mesh (multipart file + target),
// reached through the /upstream passthrough (ADR-0020). Exists because
// Hunyuan3D's api_server always returns GLB — STL for the printer
// pipeline is produced by this conversion hop.
package llamaswap

import (
	"context"
	"fmt"
	"net/http"
	"strings"

	"gitea.stevedudenhoeffer.com/steve/majordomo/llm"
	"gitea.stevedudenhoeffer.com/steve/majordomo/meshgen"
)

// MeshConverter implements meshgen.ConverterProvider.
func (p *Provider) MeshConverter(id string) (meshgen.Converter, error) {
	if err := p.requireBaseURL(); err != nil {
		return nil, err
	}
	return &meshConverter{p: p, id: id}, nil
}

type meshConverter struct {
	p  *Provider
	id string
}

// Convert implements meshgen.Converter.
func (m *meshConverter) Convert(ctx context.Context, mesh meshgen.Mesh, format string) (*meshgen.Result, error) {
	if len(mesh.Data) == 0 {
		return nil, fmt.Errorf("%w: mesh conversion requires mesh bytes", llm.ErrUnsupported)
	}
	format = strings.ToLower(strings.TrimSpace(format))
	mimeType, ok := meshFormats[format]
	if !ok {
		return nil, fmt.Errorf("%w: unsupported mesh format %q (want glb, stl, or obj)", llm.ErrUnsupported, format)
	}
	path, err := upstreamPath(m.id, "/v1/convert_mesh")
	if err != nil {
		return nil, err
	}
	filename := "mesh." + mesh.Format
	if mesh.Format == "" {
		filename = "mesh"
	}
	body, contentType, err := buildMultipart("build mesh-convert form",
		filePart{field: "file", filename: filename, data: mesh.Data},
		[]formField{{"target", format, true}})
	if err != nil {
		return nil, err
	}
	raw, _, err := m.p.doRaw(ctx, http.MethodPost, path, m.id, contentType, body, maxMeshResponseBytes)
	if err != nil {
		return nil, err
	}
	if len(raw) == 0 {
		return nil, &llm.APIError{Provider: m.p.name, Model: m.id, Message: "mesh conversion returned no data"}
	}
	actualFormat, actualMIME := sniffMeshFormat(raw, format, mimeType)
	return &meshgen.Result{Mesh: meshgen.Mesh{Data: raw, Format: actualFormat, MIME: actualMIME}}, nil
}