package config

import (
	"fmt"
	"io"
	"os"
	"path/filepath"

	"gopkg.in/yaml.v3"
)

// LoadPipeline loads pipeline configuration from a YAML file with strict field checking.
func LoadPipeline(path string) (*PipelineConfig, error) {
	var cfg PipelineConfig
	if err := decodeStrictYAML("pipeline", path, &cfg); err != nil {
		return nil, fmt.Errorf("load pipeline config: %w", err)
	}
	return &cfg, nil
}

// LoadSession loads session configuration from a YAML file with strict field checking.
func LoadSession(path string) (*SessionConfig, error) {
	var cfg SessionConfig
	if err := decodeStrictYAML("session", path, &cfg); err != nil {
		return nil, fmt.Errorf("load session config: %w", err)
	}
	return &cfg, nil
}

// Load loads and resolves combined pipeline and session configuration.
func Load(pipelinePath, sessionPath string) (*Config, error) {
	pipelineCfg, err := LoadPipeline(pipelinePath)
	if err != nil {
		return nil, err
	}

	sessionCfg, err := LoadSession(sessionPath)
	if err != nil {
		return nil, err
	}

	return &Config{
		Pipeline:     pipelineCfg,
		Session:      sessionCfg,
		PipelinePath: pipelinePath,
		SessionPath:  sessionPath,
	}, nil
}

func decodeStrictYAML(kind, path string, out any) error {
	f, err := os.Open(path)
	if err != nil {
		return fmt.Errorf("%s file %q: open: %w", kind, path, err)
	}
	defer f.Close()

	dec := yaml.NewDecoder(f)
	dec.KnownFields(true)
	if err := dec.Decode(out); err != nil {
		return fmt.Errorf("%s file %q: strict decode failed: %w", kind, path, err)
	}

	var extra any
	if err := dec.Decode(&extra); err != nil && err != io.EOF {
		return fmt.Errorf("%s file %q: trailing content decode failed: %w", kind, path, err)
	}

	return nil
}

func shortName(path, fallback string) string {
	base := filepath.Base(path)
	if base == "." || base == string(filepath.Separator) {
		return fallback
	}
	return base
}