// SPDX-License-Identifier: EUPL-1.2

// OS-aware filesystem path operations for the Core framework.
// Uses Env("DS") for the separator and Core string primitives
// for path manipulation. filepath imported only for PathGlob.
//
// Path anchors relative segments to DIR_HOME:
//
//	core.Path("Code", ".core")     // "/Users/snider/Code/.core"
//	core.Path("/tmp", "workspace") // "/tmp/workspace"
//	core.Path()                    // "/Users/snider"
//
// Path component helpers:
//
//	core.PathBase("/Users/snider/Code/core")  // "core"
//	core.PathDir("/Users/snider/Code/core")   // "/Users/snider/Code"
//	core.PathExt("main.go")                   // ".go"
package core

import "path/filepath"

// Path builds a clean, absolute filesystem path from segments.
// Uses Env("DS") for the OS directory separator.
// Relative paths are anchored to DIR_HOME. Absolute paths pass through.
//
//	core.Path("Code", ".core")      // "/Users/snider/Code/.core"
//	core.Path("/tmp", "workspace")  // "/tmp/workspace"
//	core.Path()                     // "/Users/snider"
func Path(segments ...string) string {
	ds := Env("DS")
	home := Env("DIR_HOME")
	if home == "" {
		home = "."
	}
	if len(segments) == 0 {
		return home
	}
	p := Join(ds, segments...)
	if PathIsAbs(p) {
		return CleanPath(p, ds)
	}
	return CleanPath(home+ds+p, ds)
}

// PathBase returns the last element of a path.
//
//	core.PathBase("/Users/snider/Code/core")  // "core"
//	core.PathBase("deploy/to/homelab")        // "homelab"
func PathBase(p string) string {
	if p == "" {
		return "."
	}
	ds := Env("DS")
	p = TrimSuffix(p, ds)
	if p == "" {
		return ds
	}
	parts := Split(p, ds)
	return parts[len(parts)-1]
}

// PathDir returns all but the last element of a path.
//
//	core.PathDir("/Users/snider/Code/core")  // "/Users/snider/Code"
func PathDir(p string) string {
	if p == "" {
		return "."
	}
	ds := Env("DS")
	i := lastIndex(p, ds)
	if i < 0 {
		return "."
	}
	dir := p[:i]
	if dir == "" {
		return ds
	}
	return dir
}

// PathExt returns the file extension including the dot.
//
//	core.PathExt("main.go")   // ".go"
//	core.PathExt("Makefile")  // ""
func PathExt(p string) string {
	base := PathBase(p)
	i := lastIndex(base, ".")
	if i <= 0 {
		return ""
	}
	return base[i:]
}

// PathIsAbs returns true if the path is absolute.
// Handles Unix (starts with /) and Windows (drive letter like C:).
//
//	core.PathIsAbs("/tmp")     // true
//	core.PathIsAbs("C:\\tmp")  // true
//	core.PathIsAbs("relative") // false
func PathIsAbs(p string) bool {
	if p == "" {
		return false
	}
	if p[0] == '/' {
		return true
	}
	// Windows: C:\ or C:/
	if len(p) >= 3 && p[1] == ':' && (p[2] == '/' || p[2] == '\\') {
		return true
	}
	return false
}

// CleanPath removes redundant separators and resolves . and .. elements.
//
//	core.CleanPath("/tmp//file", "/")     // "/tmp/file"
//	core.CleanPath("a/b/../c", "/")       // "a/c"
func CleanPath(p, ds string) string {
	if p == "" {
		return "."
	}

	rooted := HasPrefix(p, ds)
	parts := Split(p, ds)
	var clean []string

	for _, part := range parts {
		switch part {
		case "", ".":
			continue
		case "..":
			if len(clean) > 0 && clean[len(clean)-1] != ".." {
				clean = clean[:len(clean)-1]
			} else if !rooted {
				clean = append(clean, "..")
			}
		default:
			clean = append(clean, part)
		}
	}

	result := Join(ds, clean...)
	if rooted {
		result = ds + result
	}
	if result == "" {
		if rooted {
			return ds
		}
		return "."
	}
	return result
}

// PathGlob returns file paths matching a pattern.
//
//	core.PathGlob("/tmp/agent-*.log")
func PathGlob(pattern string) []string {
	matches, _ := filepath.Glob(pattern)
	return matches
}

// lastIndex returns the index of the last occurrence of substr in s, or -1.
func lastIndex(s, substr string) int {
	if substr == "" || s == "" {
		return -1
	}
	for i := len(s) - len(substr); i >= 0; i-- {
		if s[i:i+len(substr)] == substr {
			return i
		}
	}
	return -1
}