package promptdef

import (
	"bytes"
	"context"
	"errors"
	"fmt"
	"os"
	"path/filepath"
	"strings"

	"gitea.maximumdirect.net/eric/scriptorium/internal/domain"
	"gopkg.in/yaml.v3"
)

var (
	ErrPromptDefinitionNotFound = errors.New("prompt definition not found")
	ErrInvalidYAML              = errors.New("invalid YAML format")
	ErrInvalidPromptDefinition  = errors.New("invalid prompt definition configuration")
)

type filesystemRepository struct {
	dir string
}

type promptDefinitionFile struct {
	ID             string                   `yaml:"id"`
	Version        string                   `yaml:"version"`
	DefaultProfile *string                  `yaml:"default_profile"`
	Description    string                   `yaml:"description"`
	Inputs         []promptInputFile        `yaml:"inputs"`
	Messages       []promptMessageFile      `yaml:"messages"`
	Output         promptOutputContractFile `yaml:"output"`
}

type promptInputFile struct {
	Name        string `yaml:"name"`
	Required    bool   `yaml:"required"`
	ContentType string `yaml:"content_type"`
	Description string `yaml:"description"`
}

type promptMessageFile struct {
	Role        string `yaml:"role"`
	Content     string `yaml:"content"`
	ContentFile string `yaml:"content_file"`
}

type promptOutputContractFile struct {
	Format         domain.OutputFormat   `yaml:"format"`
	ValidationMode domain.ValidationMode `yaml:"validation_mode"`
	SchemaPath     string                `yaml:"schema_path"`
	RepairAttempts int                   `yaml:"repair_attempts"`
}

func NewFilesystemRepository(dir string) Repository {
	return &filesystemRepository{dir: dir}
}

func (r *filesystemRepository) GetPromptDefinition(ctx context.Context, id string, version string) (*domain.PromptDefinition, error) {
	if strings.TrimSpace(id) == "" {
		return nil, fmt.Errorf("%w: prompt id is required", ErrInvalidPromptDefinition)
	}

	files, err := os.ReadDir(r.dir)
	if err != nil {
		return nil, fmt.Errorf("failed to read prompt definition directory: %w", err)
	}

	for _, file := range files {
		select {
		case <-ctx.Done():
			return nil, ctx.Err()
		default:
		}

		if file.IsDir() || !isYAMLFile(file.Name()) {
			continue
		}

		fullPath := filepath.Join(r.dir, file.Name())
		fileMatch := promptIDFromFileName(file.Name()) == id

		raw, err := loadPromptDefinitionFile(fullPath)
		if err != nil {
			if fileMatch {
				return nil, fmt.Errorf("%w: %s: %v", ErrInvalidYAML, file.Name(), err)
			}
			continue
		}

		def, err := normalizePromptDefinition(raw, fullPath)
		if err != nil {
			if fileMatch || strings.TrimSpace(raw.ID) == id {
				return nil, fmt.Errorf("%w: %s: %v", ErrInvalidPromptDefinition, file.Name(), err)
			}
			continue
		}

		if def.ID != id {
			continue
		}
		if version != "" && def.Version != version {
			continue
		}
		return def, nil
	}

	return nil, ErrPromptDefinitionNotFound
}

func loadPromptDefinitionFile(path string) (*promptDefinitionFile, error) {
	data, err := os.ReadFile(path)
	if err != nil {
		return nil, fmt.Errorf("failed to read prompt definition file: %w", err)
	}

	var raw promptDefinitionFile
	decoder := yaml.NewDecoder(bytes.NewReader(data))
	decoder.KnownFields(true)
	if err := decoder.Decode(&raw); err != nil {
		return nil, err
	}
	return &raw, nil
}

func normalizePromptDefinition(raw *promptDefinitionFile, sourcePath string) (*domain.PromptDefinition, error) {
	if raw == nil {
		return nil, errors.New("prompt definition is nil")
	}

	id := strings.TrimSpace(raw.ID)
	if id == "" {
		return nil, errors.New("id is required")
	}

	version := strings.TrimSpace(raw.Version)
	if version == "" {
		return nil, errors.New("version is required")
	}

	if len(raw.Messages) == 0 {
		return nil, errors.New("at least one message is required")
	}

	inputs := make([]domain.PromptInput, 0, len(raw.Inputs))
	seenInputNames := make(map[string]struct{}, len(raw.Inputs))
	for i, in := range raw.Inputs {
		name := strings.TrimSpace(in.Name)
		if name == "" {
			return nil, fmt.Errorf("input %d has empty name", i)
		}
		if _, exists := seenInputNames[name]; exists {
			return nil, fmt.Errorf("duplicate input name %q", name)
		}
		seenInputNames[name] = struct{}{}

		inputs = append(inputs, domain.PromptInput{
			Name:        name,
			Required:    in.Required,
			ContentType: strings.TrimSpace(in.ContentType),
			Description: strings.TrimSpace(in.Description),
		})
	}

	templates := make([]domain.PromptMessageTemplate, 0, len(raw.Messages))
	promptDir := filepath.Dir(sourcePath)
	for i, msg := range raw.Messages {
		role := strings.TrimSpace(msg.Role)
		if role == "" {
			return nil, fmt.Errorf("message %d role is required", i)
		}

		hasContent := strings.TrimSpace(msg.Content) != ""
		hasContentFile := strings.TrimSpace(msg.ContentFile) != ""
		if hasContent == hasContentFile {
			return nil, fmt.Errorf("message %d (%s) must set exactly one of content or content_file", i, role)
		}

		templateContent := msg.Content
		resolvedContentFile := ""
		if hasContentFile {
			resolvedPath := strings.TrimSpace(msg.ContentFile)
			if !filepath.IsAbs(resolvedPath) {
				resolvedPath = filepath.Join(promptDir, resolvedPath)
			}
			resolvedPath = filepath.Clean(resolvedPath)

			body, err := os.ReadFile(resolvedPath)
			if err != nil {
				return nil, fmt.Errorf("prompt %q message %d (%s): failed to read content_file %q: %w", id, i, role, msg.ContentFile, err)
			}
			templateContent = string(body)
			resolvedContentFile = resolvedPath
		}

		templates = append(templates, domain.PromptMessageTemplate{
			Role:        role,
			Content:     templateContent,
			ContentFile: resolvedContentFile,
		})
	}

	if !isValidOutputFormat(raw.Output.Format) {
		return nil, fmt.Errorf("invalid output format: %q", raw.Output.Format)
	}
	if !isValidValidationMode(raw.Output.ValidationMode) {
		return nil, fmt.Errorf("invalid validation mode: %q", raw.Output.ValidationMode)
	}
	if raw.Output.ValidationMode == domain.ValidationJSONSchema && strings.TrimSpace(raw.Output.SchemaPath) == "" {
		return nil, errors.New("output.schema_path is required when output.validation_mode is json_schema")
	}
	if raw.Output.RepairAttempts < 0 {
		return nil, errors.New("output.repair_attempts must be greater than or equal to 0")
	}

	defaultProfile := ""
	if raw.DefaultProfile != nil {
		defaultProfile = strings.TrimSpace(*raw.DefaultProfile)
		if defaultProfile == "" {
			return nil, errors.New("default_profile must be a non-empty string when set")
		}
	}

	return &domain.PromptDefinition{
		ID:             id,
		Version:        version,
		DefaultProfile: defaultProfile,
		Description:    strings.TrimSpace(raw.Description),
		Inputs:         inputs,
		Templates:      templates,
		OutputFormat:   raw.Output.Format,
		Validation: domain.OutputContract{
			Format:         raw.Output.Format,
			ValidationMode: raw.Output.ValidationMode,
			SchemaPath:     strings.TrimSpace(raw.Output.SchemaPath),
			RepairAttempts: raw.Output.RepairAttempts,
		},
	}, nil
}

func isYAMLFile(name string) bool {
	return strings.HasSuffix(name, ".yaml") || strings.HasSuffix(name, ".yml")
}

func promptIDFromFileName(name string) string {
	name = strings.TrimSuffix(name, ".yaml")
	name = strings.TrimSuffix(name, ".yml")
	return name
}

func isValidOutputFormat(f domain.OutputFormat) bool {
	switch f {
	case domain.FormatText, domain.FormatMarkdown, domain.FormatJSON:
		return true
	default:
		return false
	}
}

func isValidValidationMode(m domain.ValidationMode) bool {
	switch m {
	case domain.ValidationNone, domain.ValidationBasic, domain.ValidationJSON, domain.ValidationJSONSchema:
		return true
	default:
		return false
	}
}