package api_gen

import (
	"bytes"
	"go/format"
	"os"
	"path/filepath"
	"text/template"
)

// generateCLI emits a dispatch table over the generated Client: a list of
// command names and an Invoke function that decodes a JSON request body into
// the typed request and calls the matching client method. The hand-written CLI
// binary (apps/demo/cmd/atlas9api) wraps this with credential handling.
func generateCLI(outputDir string, pkg *APIPackage) error {
	tmpl := `// Code generated by api_gen. DO NOT EDIT.

package client

import (
	"context"
	"encoding/json"
	"fmt"

	"{{ .PkgPath }}"
)

// CommandNames lists every endpoint the CLI can invoke, in registration order.
var CommandNames = []string{
{{- range .Endpoints }}
	"{{ .Name }}",
{{- end }}
}

// Invoke decodes body into the request type for the named command, calls the
// corresponding client method, and returns the typed response. An unknown name
// returns an error.
func Invoke(ctx context.Context, c *Client, name string, body []byte) (any, error) {

	switch name {
{{- range .Endpoints }}
	case "{{ .Name }}":
		var req {{ $.PkgName }}.{{ .ReqType }}
		if len(body) > 0 {
			if err := json.Unmarshal(body, &req); err != nil {
				return nil, fmt.Errorf("decoding request: %w", err)
			}
		}
		return c.{{ .Name }}(ctx, &req)
{{- end }}
	default:
		return nil, fmt.Errorf("unknown command: %s", name)
	}
}
`

	tmplObj := template.Must(template.New("cli").Parse(tmpl))

	var buf bytes.Buffer
	if err := tmplObj.Execute(&buf, pkg); err != nil {
		return err
	}

	formatted, err := format.Source(buf.Bytes())
	if err != nil {
		return err
	}

	return os.WriteFile(filepath.Join(outputDir, "cli_gen.go"), formatted, 0644)
}