Elep

// Walk through the file-system "database" of installed
// packages, and create a data object related to the
// installed versions of each package.

/*
This will traverse through all node_modules folders,
resolving the dependencies object to the object corresponding to
the package that meets that dep, or just the version/range if
unmet.

Assuming that you had this folder structure:

/path/to
+-- package.json { name = "root" }
`-- node_modules
    +-- foo {bar, baz, asdf}
    | +-- node_modules
    |   +-- bar { baz }
    |   `-- baz
    `-- asdf

where "foo" depends on bar, baz, and asdf, bar depends on baz,
and bar and baz are bundled with foo, whereas "asdf" is at
the higher level (sibling to foo), you'd get this object structure:

{ <package.json data>
, path: "/path/to"
, parent: null
, dependencies:
  { foo :
    { version: "1.2.3"
    , path: "/path/to/node_modules/foo"
    , parent: <Circular: root>
    , dependencies:
      { bar:
        { parent: <Circular: foo>
        , path: "/path/to/node_modules/foo/node_modules/bar"
        , version: "2.3.4"
        , dependencies: { baz: <Circular: foo.dependencies.baz> }
        }
      , baz: { ... }
      , asdf: <Circular: asdf>
      }
    }
  , asdf: { ... }
  }
}

Unmet deps are left as strings.
Extraneous deps are marked with extraneous:true
deps that don't meet a requirement are marked with invalid:true
deps that don't meet a peer requirement are marked with peerInvalid:true

to READ(packagefolder, parentobj, name, reqver)
obj = read package.json
installed = ./node_modules/*
if parentobj is null, and no package.json
  obj = {dependencies:{<installed>:ANY}}
deps = Object.keys(obj.dependencies)
obj.path = packagefolder
obj.parent = parentobj
if name, && obj.name !== name, obj.invalid = true
if reqver, && obj.version !satisfies reqver, obj.invalid = true
if !reqver && parentobj, obj.extraneous = true
for each folder in installed
  obj.dependencies[folder] = READ(packagefolder+node_modules+folder,
                                  obj, folder, obj.dependencies[folder])
# walk tree to find unmet deps
for each dep in obj.dependencies not in installed
  r = obj.parent
  while r
    if r.dependencies[dep]
      if r.dependencies[dep].verion !satisfies obj.dependencies[dep]
        WARN
        r.dependencies[dep].invalid = true
      obj.dependencies[dep] = r.dependencies[dep]
      r = null
    else r = r.parent
return obj

TODO:
1. Find unmet deps in parent directories, searching as node does up
as far as the left-most node_modules folder.
2. Ignore anything in node_modules that isn't a package folder.

try {
  var fs = require("graceful-fs")
} catch (er) {
  var fs = require("fs")
}

var path = require("path")
var asyncMap = require("slide").asyncMap
var semver = require("semver")
var readJson = require("read-package-json")
var url = require("url")
var util = require("util")
var extend = require("util-extend")

var debug = require("debuglog")("read-installed")

var readdir = require("readdir-scoped-modules")

// Sentinel catch-all version constraint used when a dependency is not
// listed in the package.json file.
var ANY = {}

module.exports = readInstalled

function readInstalled (folder, opts, cb) {
  if (typeof opts === 'function') {
    cb = opts
    opts = {}
  } else {
    opts = extend({}, opts)
  }

if (typeof opts.depth !== 'number')
    opts.depth = Infinity

opts.depth = Math.max(0, opts.depth)

if (typeof opts.log !== 'function')
    opts.log = function () {}

opts.dev = !!opts.dev
  opts.realpathSeen = {}
  opts.findUnmetSeen = []

readInstalled_(folder, null, null, null, 0, opts, function (er, obj) {
    if (er) return cb(er)
    // now obj has all the installed things, where they're installed
    // figure out the inheritance links, now that the object is built.
    resolveInheritance(obj, opts)
    obj.root = true
    unmarkExtraneous(obj, opts)
    cb(null, obj)
  })
}

function readInstalled_ (folder, parent, name, reqver, depth, opts, cb) {
  var installed
    , obj
    , real
    , link
    , realpathSeen = opts.realpathSeen

readdir(path.resolve(folder, "node_modules"), function (er, i) {
    // error indicates that nothing is installed here
    if (er) i = []
    installed = i.filter(function (f) { return f.charAt(0) !== "." })
    next()
  })

readJson(path.resolve(folder, "package.json"), function (er, data) {
    obj = copy(data)

if (!parent) {
      obj = obj || true
      er = null
    }
    return next(er)
  })

fs.lstat(folder, function (er, st) {
    if (er) {
      if (!parent) real = true
      return next(er)
    }
    fs.realpath(folder, function (er, rp) {
      debug("realpath(%j) = %j", folder, rp)
      real = rp
      if (st.isSymbolicLink()) link = rp
      next(er)
    })
  })

var errState = null
    , called = false
  function next (er) {
    if (errState) return
    if (er) {
      errState = er
      return cb(null, [])
    }
    debug('next', installed, obj && typeof obj, name, real)
    if (!installed || !obj || !real || called) return
    called = true
    if (realpathSeen[real]) return cb(null, realpathSeen[real])
    if (obj === true) {
      obj = {dependencies:{}, path:folder}
      installed.forEach(function (i) { obj.dependencies[i] = ANY })
    }
    if (name && obj.name !== name) obj.invalid = true
    obj.realName = name || obj.name
    obj.dependencies = obj.dependencies || {}

// At this point, figure out what dependencies we NEED to get met
    obj._dependencies = copy(obj.dependencies)

if (reqver === ANY) {
      // We were unable to determine the required version of this
      // dependency from the package.json file, but we now know its actual
      // version, so treat that version as the required version to avoid
      // marking the dependency as invalid below. See #40.
      reqver = obj.version;
    }

// "foo":"http://blah" and "foo":"latest" are always presumed valid
    if (reqver
        && semver.validRange(reqver, true)
        && !semver.satisfies(obj.version, reqver, true)) {
      obj.invalid = true
    }

// Mark as extraneous at this point.
    // This will be un-marked in unmarkExtraneous, where we mark as
    // not-extraneous everything that is required in some way from
    // the root object.
    obj.extraneous = true

obj.path = obj.path || folder
    obj.realPath = real
    obj.link = link
    if (parent && !obj.link) obj.parent = parent
    realpathSeen[real] = obj
    obj.depth = depth
    //if (depth >= opts.depth) return cb(null, obj)
    asyncMap(installed, function (pkg, cb) {
      var rv = obj.dependencies[pkg]
      if (!rv && obj.devDependencies && opts.dev)
        rv = obj.devDependencies[pkg]

if (depth > opts.depth) {
        obj.dependencies = {}
        return cb(null, obj)
      }

readInstalled_( path.resolve(folder, "node_modules/"+pkg)
                    , obj, pkg, obj.dependencies[pkg], depth + 1, opts
                    , cb )

}, function (er, installedData) {
      if (er) return cb(er)
      installedData.forEach(function (dep) {
        obj.dependencies[dep.realName] = dep
      })

// any strings here are unmet things.  however, if it's
      // optional, then that's fine, so just delete it.
      if (obj.optionalDependencies) {
        Object.keys(obj.optionalDependencies).forEach(function (dep) {
          if (typeof obj.dependencies[dep] === "string") {
            delete obj.dependencies[dep]
          }
        })
      }
      return cb(null, obj)
    })
  }
}

// starting from a root object, call findUnmet on each layer of children
var riSeen = []
function resolveInheritance (obj, opts) {
  if (typeof obj !== "object") return
  if (riSeen.indexOf(obj) !== -1) return
  riSeen.push(obj)
  if (typeof obj.dependencies !== "object") {
    obj.dependencies = {}
  }
  Object.keys(obj.dependencies).forEach(function (dep) {
    findUnmet(obj.dependencies[dep], opts)
  })
  Object.keys(obj.dependencies).forEach(function (dep) {
    if (typeof obj.dependencies[dep] === "object") {
      resolveInheritance(obj.dependencies[dep], opts)
    } else {
      debug("unmet dep! %s %s@%s", obj.name, dep, obj.dependencies[dep])
    }
  })
  findUnmet(obj, opts)
}

// find unmet deps by walking up the tree object.
// No I/O
function findUnmet (obj, opts) {
  var findUnmetSeen = opts.findUnmetSeen
  if (findUnmetSeen.indexOf(obj) !== -1) return
  findUnmetSeen.push(obj)
  debug("find unmet parent=%s obj=", obj.parent && obj.parent.name, obj.name || obj)
  var deps = obj.dependencies = obj.dependencies || {}

debug(deps)
  Object.keys(deps)
    .filter(function (d) { return typeof deps[d] === "string" })
    .forEach(function (d) {
      var found = findDep(obj, d)
      debug("finding dep %j", d, found && found.name || found)
      // "foo":"http://blah" and "foo":"latest" are always presumed valid
      if (typeof deps[d] === "string" &&
          semver.validRange(deps[d], true) &&
          found &&
          !semver.satisfies(found.version, deps[d], true)) {
        // the bad thing will happen
        opts.log( "unmet dependency"
                , obj.path + " requires "+d+"@'"+deps[d]
                + "' but will load\n"
                + found.path+",\nwhich is version "+found.version )
        found.invalid = true
      }
      if (found) {
        deps[d] = found
      }
    })

var peerDeps = obj.peerDependencies = obj.peerDependencies || {}
  Object.keys(peerDeps).forEach(function (d) {
    var dependency

if (!obj.parent) {
      dependency = obj.dependencies[d]

// read it as a missing dep
      if (!dependency) {
        obj.dependencies[d] = peerDeps[d]
      }
    } else {
      var r = obj.parent
      while (r && !dependency) {
        dependency = r.dependencies && r.dependencies[d]
        r = r.link ? null : r.parent
      }
    }

if (!dependency) {
      // mark as a missing dep!
      obj.dependencies[d] = peerDeps[d]
    } else if (!semver.satisfies(dependency.version, peerDeps[d], true)) {
      dependency.peerInvalid = true
    }
  })

return obj
}

function unmarkExtraneous (obj, opts) {
  // Mark all non-required deps as extraneous.
  // start from the root object and mark as non-extraneous all modules
  // that haven't been previously flagged as extraneous then propagate
  // to all their dependencies

obj.extraneous = false

var deps = obj._dependencies || []
  if (opts.dev && obj.devDependencies && (obj.root || obj.link)) {
    Object.keys(obj.devDependencies).forEach(function (k) {
      deps[k] = obj.devDependencies[k]
    })
  }

if (obj.peerDependencies) {
    Object.keys(obj.peerDependencies).forEach(function (k) {
      deps[k] = obj.peerDependencies[k]
    })
  }

debug("not extraneous", obj._id, deps)
  Object.keys(deps).forEach(function (d) {
    var dep = findDep(obj, d)
    if (dep && dep.extraneous) {
      unmarkExtraneous(dep, opts)
    }
  })
}

// Find the one that will actually be loaded by require()
// so we can make sure it's valid etc.
function findDep (obj, d) {
  var r = obj
    , found = null
  while (r && !found) {
    // if r is a valid choice, then use that.
    // kinda weird if a pkg depends on itself, but after the first
    // iteration of this loop, it indicates a dep cycle.
    if (typeof r.dependencies[d] === "object") {
      found = r.dependencies[d]
    }
    if (!found && r.realName === d) found = r
    r = r.link ? null : r.parent
  }
  return found
}

function copy (obj) {
  if (!obj || typeof obj !== 'object') return obj
  if (Array.isArray(obj)) return obj.map(copy)

var o = {}
  for (var i in obj) o[i] = copy(obj[i])
  return o
}