fetch.go

package main

import (
	"fmt"
	"go/build"
	"net/url"
	"sort"

	"github.com/constabulary/gb/vendor"
)

func keys(m map[string]bool) []string {
	var s []string
	for k := range m {
		s = append(s, k)
	}
	return s
}

func pkgs(m map[string]*vendor.Pkg) []*vendor.Pkg {
	var p []*vendor.Pkg
	for _, v := range m {
		p = append(p, v)
	}
	return p
}

func findMissing(pkgs []*vendor.Pkg, dsm map[string]*vendor.Depset) *string {
	missing := make(map[string]bool)
	imports := make(map[string]*vendor.Pkg)
	for _, s := range dsm {
		for _, p := range s.Pkgs {
			imports[p.ImportPath] = p
		}
	}

	// make fake C package for cgo
	imports["C"] = &vendor.Pkg{
		Depset: nil, // probably a bad idea
		Package: &build.Package{
			Name: "C",
		},
	}
	stk := make(map[string]bool)
	push := func(v string) {
		if stk[v] {
			panic(fmt.Sprintln("import loop:", v, stk))
		}
		stk[v] = true
	}
	pop := func(v string) {
		if !stk[v] {
			panic(fmt.Sprintln("impossible pop:", v, stk))
		}
		delete(stk, v)
	}

	// checked records import paths who's dependencies are all present
	checked := make(map[string]bool)

	var fn func(string)
	fn = func(importpath string) {
		p, ok := imports[importpath]
		if !ok {
			missing[importpath] = true
			return
		}

		// have we already walked this arm, if so, skip it
		if checked[importpath] {
			return
		}

		sz := len(missing)
		push(importpath)
		for _, i := range p.Imports {
			if i == importpath {
				continue
			}
			fn(i)
		}

		// if the size of the missing map has not changed
		// this entire subtree is complete, mark it as such
		if len(missing) == sz {
			checked[importpath] = true
		}
		pop(importpath)
	}
	for _, pkg := range pkgs {
		fn(pkg.ImportPath)
	}
	if len(missing) == 0 {
		return nil
	}
	// sort keys in ascending order, so the shortest missing import path
	// with be fetched first.
	keys := keys(missing)
	sort.Strings(keys)
	return &keys[0]
}

// stripscheme removes any scheme components from url like paths.
func stripscheme(path string) string {
	u, err := url.Parse(path)
	if err != nil {
		panic(err)
	}
	return u.Host + u.Path
}