// Package workspace provides workspace detection and management.
package workspace

import (
	"errors"
	"fmt"
	"os"
	"path/filepath"
)

// ErrNotFound indicates no workspace was found.
var ErrNotFound = errors.New("not in a Gas Town workspace")

// Markers used to detect a Gas Town workspace.
const (
	// PrimaryMarker is the main config file that identifies a workspace.
	PrimaryMarker = "config/town.json"

	// AlternativePrimaryMarker is the town-level mayor config file.
	// This distinguishes a town mayor from a rig-level mayor clone.
	AlternativePrimaryMarker = "mayor/config.json"

	// SecondaryMarker is an alternative indicator at the town level.
	// Note: This can match rig-level mayors too, so we continue searching
	// upward after finding this to look for primary markers.
	SecondaryMarker = "mayor"
)

// Find locates the town root by walking up from the given directory.
// It looks for config/town.json or mayor/config.json (primary markers)
// or mayor/ directory (secondary marker).
//
// To avoid matching rig-level mayor directories, we continue searching
// upward after finding a secondary marker, preferring primary matches.
func Find(startDir string) (string, error) {
	// Resolve to absolute path and follow symlinks
	absDir, err := filepath.Abs(startDir)
	if err != nil {
		return "", fmt.Errorf("resolving path: %w", err)
	}

	absDir, err = filepath.EvalSymlinks(absDir)
	if err != nil {
		return "", fmt.Errorf("evaluating symlinks: %w", err)
	}

	// Track the first secondary match in case no primary is found
	var secondaryMatch string

	// Walk up the directory tree
	current := absDir
	for {
		// Check for primary marker (config/town.json)
		primaryPath := filepath.Join(current, PrimaryMarker)
		if _, err := os.Stat(primaryPath); err == nil {
			return current, nil
		}

		// Check for alternative primary marker (mayor/config.json)
		// This distinguishes a town-level mayor from a rig-level mayor clone
		altPrimaryPath := filepath.Join(current, AlternativePrimaryMarker)
		if _, err := os.Stat(altPrimaryPath); err == nil {
			return current, nil
		}

		// Check for secondary marker (mayor/ directory)
		// Don't return immediately - continue searching for primary markers
		if secondaryMatch == "" {
			secondaryPath := filepath.Join(current, SecondaryMarker)
			info, err := os.Stat(secondaryPath)
			if err == nil && info.IsDir() {
				secondaryMatch = current
			}
		}

		// Move to parent directory
		parent := filepath.Dir(current)
		if parent == current {
			// Reached filesystem root - return secondary match if found
			return secondaryMatch, nil
		}
		current = parent
	}
}

// FindOrError is like Find but returns a user-friendly error if not found.
func FindOrError(startDir string) (string, error) {
	root, err := Find(startDir)
	if err != nil {
		return "", err
	}
	if root == "" {
		return "", ErrNotFound
	}
	return root, nil
}

// FindFromCwd locates the town root from the current working directory.
func FindFromCwd() (string, error) {
	cwd, err := os.Getwd()
	if err != nil {
		return "", fmt.Errorf("getting current directory: %w", err)
	}
	return Find(cwd)
}

// FindFromCwdOrError is like FindFromCwd but returns an error if not found.
func FindFromCwdOrError() (string, error) {
	cwd, err := os.Getwd()
	if err != nil {
		return "", fmt.Errorf("getting current directory: %w", err)
	}
	return FindOrError(cwd)
}

// IsWorkspace checks if the given directory is a Gas Town workspace root.
// A directory is a workspace if it has primary markers (config/town.json
// or mayor/config.json) or a secondary marker (mayor/ directory).
func IsWorkspace(dir string) (bool, error) {
	absDir, err := filepath.Abs(dir)
	if err != nil {
		return false, fmt.Errorf("resolving path: %w", err)
	}

	// Check for primary marker
	primaryPath := filepath.Join(absDir, PrimaryMarker)
	if _, err := os.Stat(primaryPath); err == nil {
		return true, nil
	}

	// Check for alternative primary marker
	altPrimaryPath := filepath.Join(absDir, AlternativePrimaryMarker)
	if _, err := os.Stat(altPrimaryPath); err == nil {
		return true, nil
	}

	// Check for secondary marker
	secondaryPath := filepath.Join(absDir, SecondaryMarker)
	info, err := os.Stat(secondaryPath)
	if err == nil && info.IsDir() {
		return true, nil
	}

	return false, nil
}