package review

import (
	"embed"
	"encoding/json"
	"fmt"
	"os"
	"path/filepath"
	"strings"
)

//go:embed personas/*.json
var embeddedPersonas embed.FS

// Persona defines a specialized review role with focused expertise.
type Persona struct {
	Name         string   `json:"name"`
	DisplayName  string   `json:"display_name"`
	ModelPref    string   `json:"model_preference,omitempty"`
	Identity     string   `json:"identity"`
	Focus        []string `json:"focus"`
	Ignore       []string `json:"ignore"`
	Severity     Severity `json:"severity"`
	OutputFormat string   `json:"output_format,omitempty"`
}

// Severity defines what constitutes each severity level for this persona.
// These are prompt guidance for the LLM, not output format changes.
type Severity struct {
	Major string `json:"major"`
	Minor string `json:"minor"`
	Nit   string `json:"nit"`
}

// LoadPersona loads a persona from a file path.
func LoadPersona(path string) (*Persona, error) {
	data, err := os.ReadFile(path)
	if err != nil {
		return nil, fmt.Errorf("read persona file %s: %w", path, err)
	}
	return parsePersona(data, path)
}

// LoadBuiltinPersona loads a built-in persona by name.
// Returns an error if the persona doesn't exist.
func LoadBuiltinPersona(name string) (*Persona, error) {
	filename := name + ".json"
	data, err := embeddedPersonas.ReadFile(filepath.Join("personas", filename))
	if err != nil {
		available := ListBuiltinPersonas()
		return nil, fmt.Errorf("unknown built-in persona %q (available: %s)", name, strings.Join(available, ", "))
	}
	return parsePersona(data, "builtin:"+name)
}

// ListBuiltinPersonas returns the names of all built-in personas.
func ListBuiltinPersonas() []string {
	entries, err := embeddedPersonas.ReadDir("personas")
	if err != nil {
		return nil
	}
	var names []string
	for _, e := range entries {
		if e.IsDir() {
			continue
		}
		name := e.Name()
		if strings.HasSuffix(name, ".json") {
			names = append(names, strings.TrimSuffix(name, ".json"))
		}
	}
	return names
}

func parsePersona(data []byte, source string) (*Persona, error) {
	var p Persona
	if err := json.Unmarshal(data, &p); err != nil {
		return nil, fmt.Errorf("parse persona %s: %w", source, err)
	}
	if err := validatePersona(&p, source); err != nil {
		return nil, err
	}
	return &p, nil
}

func validatePersona(p *Persona, source string) error {
	if p.Name == "" {
		return fmt.Errorf("persona %s: name is required", source)
	}
	if p.Identity == "" {
		return fmt.Errorf("persona %s: identity is required", source)
	}
	// DisplayName defaults to Name if not set
	if p.DisplayName == "" {
		p.DisplayName = p.Name
	}
	return nil
}