package review

import (
	"context"
	"log/slog"
	"strings"

	"gitea.weiker.me/rodin/review-bot/vcs"
)

// RepoPersonaPath is the directory path where repo-specific personas are stored.
const RepoPersonaPath = ".review-bot/personas"

// LoadRepoPersonas fetches personas from a repository's .review-bot/personas/ directory.
// Returns an empty map (not nil) if the directory doesn't exist or is empty.
// Individual parse failures are logged and skipped; the remaining personas are still returned.
// Auth errors and other non-404 errors are propagated.
// Files exceeding MaxPersonaFileSize are rejected to prevent resource exhaustion.
func LoadRepoPersonas(ctx context.Context, client vcs.FileReader, owner, repo string) (map[string]*Persona, error) {
	result := make(map[string]*Persona)

	entries, err := client.ListContents(ctx, owner, repo, RepoPersonaPath)
	if err != nil {
		// Check if this is a 404 (directory doesn't exist) - expected case
		if isNotFoundError(err) {
			slog.Debug("no repo personas directory found", "repo", owner+"/"+repo)
			return result, nil
		}
		// Other errors (auth, server) should propagate
		return nil, err
	}

	if len(entries) == 0 {
		slog.Debug("repo personas directory is empty", "repo", owner+"/"+repo)
		return result, nil
	}

	for _, entry := range entries {
		if entry.Type != "file" {
			continue
		}
		// Only process YAML files
		if !isYAMLFile(entry.Name) {
			continue
		}

		content, err := client.GetFileContent(ctx, owner, repo, entry.Path, "")
		if err != nil {
			slog.Warn("could not fetch repo persona file",
				"file", entry.Path,
				"repo", owner+"/"+repo,
				"error", err)
			continue
		}

		// Enforce size limit before parsing to prevent resource exhaustion
		if len(content) > MaxPersonaFileSize {
			slog.Warn("repo persona file exceeds maximum size",
				"file", entry.Path,
				"repo", owner+"/"+repo,
				"size", len(content),
				"max", MaxPersonaFileSize)
			continue
		}

		persona, err := ParsePersonaBytes([]byte(content), entry.Path)
		if err != nil {
			slog.Warn("could not parse repo persona file",
				"file", entry.Path,
				"repo", owner+"/"+repo,
				"error", err)
			continue
		}

		result[persona.Name] = persona
		slog.Debug("loaded repo persona",
			"name", persona.Name,
			"file", entry.Path,
			"repo", owner+"/"+repo)
	}

	return result, nil
}

// MergePersonas combines built-in personas with repo personas.
// Repo personas take precedence on name collision.
// Returns a new map; inputs are not modified.
func MergePersonas(builtin, repo map[string]*Persona) map[string]*Persona {
	result := make(map[string]*Persona, len(builtin)+len(repo))

	// Copy built-in personas first
	for name, p := range builtin {
		result[name] = p
	}

	// Overlay repo personas (override on collision)
	for name, p := range repo {
		if _, exists := result[name]; exists {
			slog.Debug("repo persona overrides built-in", "name", name)
		}
		result[name] = p
	}

	return result
}

// GetBuiltinPersonasMap returns all built-in personas as a map keyed by name.
// Returns an empty map (not nil) if loading fails.
func GetBuiltinPersonasMap() map[string]*Persona {
	result := make(map[string]*Persona)
	for _, name := range ListBuiltinPersonas() {
		p, err := LoadBuiltinPersona(name)
		if err != nil {
			slog.Warn("could not load built-in persona", "name", name, "error", err)
			continue
		}
		result[name] = p
	}
	return result
}

// isYAMLFile checks if a filename has a YAML extension.
func isYAMLFile(name string) bool {
	lower := strings.ToLower(name)
	return strings.HasSuffix(lower, ".yaml") || strings.HasSuffix(lower, ".yml")
}

// isNotFoundError checks if an error represents a 404 response.
// This uses a specific "HTTP 404" substring match rather than a generic "not found"
// match to avoid masking authentication failures or transport errors that might
// contain "not found" in their message.
func isNotFoundError(err error) bool {
	if err == nil {
		return false
	}
	return strings.Contains(err.Error(), "HTTP 404")
}