// Generate a tags file for the Go Programming Language in the format used by
// exuberant-ctags.  Can be used with the VIM editor to navigate Go source code
// files.
//
// usage: gotags filename [ filename... ] > tags
//
// Authors: michael.elkins@gmail.com, m.fellinger@gmail.com
// Date: 2010-05-17

package main

import (
  "container/vector"
  "fmt"
  "go/ast"
  "go/parser"
  "os"
  "sort"
)

var tags = vector.StringVector{}

func output_tag(name *ast.Ident, kind byte) {
  tags.Push(fmt.Sprintf("%s\t%s\t%d;\"\t%c",
    name.String(), name.Position.Filename, name.Position.Line, kind))
}

func main() {
  parse_files()

  println("!_TAG_FILE_SORTED\t1\t")
  sa := tags.Data()
  sort.SortStrings(sa)
  for _, s := range sa {
    println(s)
  }
}

const FUNC, TYPE, VAR = 'f', 't', 'v'

func parse_files() {
  for i, m := 1, len(os.Args); i < m; i++ {
    tree, ok := parser.ParseFile(os.Args[i], nil, nil, 0)
    if ok != nil {
      panic("error parsing file" + os.Args[i] + ok.String())
    }

    for _, node := range tree.Decls {
      switch n := node.(type) {
      case *ast.FuncDecl:
        output_tag(n.Name, FUNC)
      case *ast.GenDecl:
        do_gen_decl(n)
      }
    }
  }

}

func do_gen_decl(node *ast.GenDecl) {
  for _, v := range node.Specs {
    switch n := v.(type) {
    case *ast.TypeSpec:
      output_tag(n.Name, TYPE)

    case *ast.ValueSpec:
      for _, vv := range n.Names {
        output_tag(vv, VAR)
      }
    }
  }
}