// Copyright 2023 The Gitea Authors. All rights reserved.
// Copyright 2025 The Forgejo Authors. All rights reserved.
// SPDX-License-Identifier: MIT

package main

import (
	"fmt"
	"go/ast"
	goParser "go/parser"
	"go/token"
	"strconv"
	"strings"
)

func (handler Handler) handleGoTrBasicLit(fset *token.FileSet, argLit *ast.BasicLit) {
	if argLit.Kind == token.STRING {
		// extract string content
		arg, err := strconv.Unquote(argLit.Value)
		if err == nil {
			// found interesting strings
			if strings.HasSuffix(arg, ".") || strings.HasSuffix(arg, "_") {
				prep, trunc := PrepareMsgidPrefix(arg)
				if trunc {
					handler.OnWarning(fset, argLit.ValuePos, fmt.Sprintf("needed to truncate message id prefix: %s", arg))
				}
				handler.OnMsgidPrefix(fset, argLit.ValuePos, prep)
			} else {
				handler.OnMsgid(fset, argLit.ValuePos, arg)
			}
		}
	}
}

func (handler Handler) handleGoTrArgument(fset *token.FileSet, n ast.Expr) {
	if argLit, ok := n.(*ast.BasicLit); ok {
		handler.handleGoTrBasicLit(fset, argLit)
	} else if argBinExpr, ok := n.(*ast.BinaryExpr); ok {
		if argBinExpr.Op != token.ADD {
			// pass
		} else if argLit, ok := argBinExpr.X.(*ast.BasicLit); ok && argLit.Kind == token.STRING {
			// extract string content
			arg, err := strconv.Unquote(argLit.Value)
			if err == nil {
				// found interesting strings
				prep, trunc := PrepareMsgidPrefix(arg)
				if trunc {
					handler.OnWarning(fset, argLit.ValuePos, fmt.Sprintf("needed to truncate message id prefix: %s", arg))
				}
				handler.OnMsgidPrefix(fset, argLit.ValuePos, prep)
			}
		}
	}
}

// the `Handle*File` functions follow the following calling convention:
// * `fname` is the name of the input file
// * `src` is either `nil` (then the function invokes `ReadFile` to read the file)
//   or the contents of the file as {`[]byte`, or a `string`}

func (handler Handler) HandleGoFile(fname string, src any) error {
	fset := token.NewFileSet()
	node, err := goParser.ParseFile(fset, fname, src, goParser.SkipObjectResolution|goParser.ParseComments)
	if err != nil {
		return LocatedError{
			Location: fname,
			Kind:     "Go parser",
			Err:      err,
		}
	}

	ast.Inspect(node, func(n ast.Node) bool {
		// search for function calls of the form `anything.Tr(any-string-lit, ...)`

		if call, ok := n.(*ast.CallExpr); ok && len(call.Args) >= 1 {
			funSel, ok := call.Fun.(*ast.SelectorExpr)
			if !ok {
				return true
			}

			ltf, ok := handler.LocaleTrFunctions[funSel.Sel.Name]
			if !ok {
				return true
			}

			var gotUnexpectedInvoke *int

			for _, argNum := range ltf {
				if len(call.Args) < int(argNum+1) {
					argc := len(call.Args)
					gotUnexpectedInvoke = &argc
				} else {
					handler.handleGoTrArgument(fset, call.Args[int(argNum)])
				}
			}

			if gotUnexpectedInvoke != nil {
				handler.OnUnexpectedInvoke(fset, funSel.Sel.NamePos, funSel.Sel.Name, *gotUnexpectedInvoke)
			}
		} else if composite, ok := n.(*ast.CompositeLit); ok {
			ident, ok := composite.Type.(*ast.Ident)
			if !ok {
				return true
			}

			// special case: models/unit/unit.go
			if strings.HasSuffix(fname, "unit.go") && ident.Name == "Unit" && len(composite.Elts) == 6 {
				// NameKey has index 2
				//   invoked like '{{ctx.Locale.Tr $unit.NameKey}}'
				nameKey, ok := composite.Elts[2].(*ast.BasicLit)
				if !ok || nameKey.Kind != token.STRING {
					handler.OnWarning(fset, composite.Elts[2].Pos(), "unexpected initialization of 'Unit'")
					return true
				}

				// extract string content
				arg, err := strconv.Unquote(nameKey.Value)
				if err == nil {
					// found interesting strings
					handler.OnMsgid(fset, nameKey.ValuePos, arg)
				}
			}
		} else if function, ok := n.(*ast.FuncDecl); ok {
			matches := false
			if function.Doc != nil {
				for _, comment := range function.Doc.List {
					if strings.TrimSpace(comment.Text) == "//llu:returnsTrKey" {
						matches = true
						break
					}
				}
			}
			if !matches {
				return true
			}
			results := function.Type.Results.List
			if len(results) != 1 {
				handler.OnWarning(fset, function.Type.Func, fmt.Sprintf("function %s has unexpected return type; expected single return value", function.Name.Name))
				return true
			}

			ast.Inspect(function.Body, func(n ast.Node) bool {
				// search for return stmts
				// TODO: what about nested functions?
				if ret, ok := n.(*ast.ReturnStmt); ok {
					for _, res := range ret.Results {
						ast.Inspect(res, func(n ast.Node) bool {
							if expr, ok := n.(ast.Expr); ok {
								handler.handleGoTrArgument(fset, expr)
							}
							return true
						})
					}
					return false
				}
				return true
			})
			return true
		} else if decl, ok := n.(*ast.GenDecl); ok && (decl.Tok == token.CONST || decl.Tok == token.VAR) {
			matches := false
			if decl.Doc != nil {
				for _, comment := range decl.Doc.List {
					if strings.TrimSpace(comment.Text) == "// llu:TrKeys" {
						matches = true
						break
					}
				}
			}
			if !matches {
				return true
			}
			for _, spec := range decl.Specs {
				// interpret all contained strings as message IDs
				ast.Inspect(spec, func(n ast.Node) bool {
					if argLit, ok := n.(*ast.BasicLit); ok {
						handler.handleGoTrBasicLit(fset, argLit)
						return false
					}
					return true
				})
			}
		}

		return true
	})

	return nil
}