package interp

import (
	"fmt"
	"unsafe"
)

var debug bool = false

var err_num_args *error_t = &error_t{msg: "wrong number of arguments"}

/*
	   value stack (p.vstack)

		           <--- SP (p.vsp)
		    ARG1
		    ARG0
		    NAME
			RET

		evaluation stack (p.ctx)
*/

func (p *process_t) push_cnode_value(val *Cnode_t) error {
	if p.vsp >= cap(p.vstack) {
		return fmt.Errorf("stack full")
	}

	p.vstack[p.vsp] = val
	p.vsp++
	p.ctx.count++
	//fmt.Printf("push_cnode_value = ctx.count => %d\n", p.ctx.count)

	return nil
}

func (p *process_t) push_string_value(val string) error {
	if p.vsp >= cap(p.vstack) {
		return fmt.Errorf("stack full")
	}

	p.vstack[p.vsp] = &val
	p.vsp++
	p.ctx.count++
	//fmt.Printf("push_string_value = ctx.count => %d\n", p.ctx.count)
	return nil
}

func (p *process_t) merge_top_values() error {
	var new_val string
	var v1, v2 *string

	if p.vsp < 2 {
		return fmt.Errorf("stack corrupt")
	}

	v1, _ = p.vstack[p.vsp-2].(*string)
	v2, _ = p.vstack[p.vsp-1].(*string)
	//new_val = *(*string)(p.vstack[p.vsp-2]) + *(*string)(p.vstack[p.vsp-1])
	new_val = *v1 + *v2
	p.vsp--
	p.vstack[p.vsp] = nil
	p.vstack[p.vsp-1] = unsafe.Pointer(&new_val)
	p.ctx.count--

	if debug {
		fmt.Printf("merge_top_values = ctx.count => %d\n", p.ctx.count)
	}
	return nil
}

func (p *process_t) pop_value() Value_t {
	var v Value_t
	p.vsp--
	v = p.vstack[p.vsp]
	p.vstack[p.vsp] = nil
	return v
}

func (p *process_t) call() error {
	var (
		proc   func(*process_t) error
		callee *string
	)

	callee = p.GetCalleeName()

	if debug {
		fmt.Printf("calling..... [%s]\n", *callee)
	}

	// TODO: use a map
	switch *callee {
	case "if":
		proc = proc_if
	case "puts":
		proc = proc_puts
	case "true":
		proc = proc_true
	case "false":
		proc = proc_false
	case "null":
		proc = proc_null
	default:
		proc = proc_unknown
	}
	return proc(p)
}

func (p *process_t) GetCalleeName() *string {
	var v *string
	v, _ = (p.vstack[p.vsp-p.ctx.count+1]).(*string)
	return v
}

func (p *process_t) GetArg(idx int) Value_t {
	return (p.vstack[p.vsp-p.ctx.count+2+idx])
}

func (p *process_t) GetNumArgs() int {
	return p.ctx.count - 2
}

func (p *process_t) Return(val Value_t) {
	p.vstack[p.vsp-p.ctx.count] = val
}

func (p *process_t) push_context(node *Cnode_t, container_node *Cnode_t) {
	if debug {
		fmt.Printf("PUSHING CONTEXT.....\n")
	}
	p.ctx = &context_t{count: 0, parent_ctx: p.ctx, parent_node: node, container_node: container_node}
}

func (p *process_t) pop_context(clear_vstack bool) (*Cnode_t, *Cnode_t) {
	var (
		i         int
		node      *Cnode_t
		container *Cnode_t
	)

	if debug {
		fmt.Printf("POPPING CONTEXT.....is_stmt/clear_vstack[%v]\n", clear_vstack)
	}

	node = p.ctx.parent_node
	container = p.ctx.container_node

	if clear_vstack { // TODO: use the conttext type instead... may be able to use container_node.code???
		// clean up the unused part of the stack
		for i = 1; i < p.ctx.count; i++ {
			p.vstack[p.vsp-p.ctx.count+i] = nil
		}

		// pop off the cleaned arguments
		p.vsp -= p.ctx.count - 1 // keep the return value in the stack
	}
	p.ctx = p.ctx.parent_ctx

	//	if p.ctx != nil {
	//		p.ctx.count++ // let the return value be the argument to the caller
	//	}

	return node, container
}

func (interp *Interp) dump_vstack(p *process_t) {
	fmt.Printf("p.VSP => %d\n", p.vsp)
	for i := 0; i < p.vsp; i++ {
		/*
			x := uintptr(p.vstack[i])
			if x&1 == 0 {
				// string value
				fmt.Printf(" %d => [%s]\n", i, *(*string)(p.vstack[i]))
			} else {
				// cnode value
				fmt.Printf(" %d => cnode %p", i, p.vstack[i]) // TODO: strip 1 off
			}*/
		switch t := p.vstack[i].(type) {
		case *string:
			fmt.Printf(" %d => [%s]\n", i, t)
		case *Cnode_t:
			fmt.Printf(" %d => ", i)
			interp.dump_cnodes(t, false)
			fmt.Printf("\n")
		default:
			panic("internal error - unrecognized value")
		}
	}
}

/*
puts "hello" world

	[STMT]
		[TEXT|puts] [DQUOTE] [TEXT|world]
	                     [TEXT|hello]

[puts 1 2; puts 1] 999

	[STMT]
	    [BRACKET] [TEXT|999]
		   [STMT]
		      [TEXT|puts] [TEXT|1] [TEXT|2]
		   [STMT]
		      [TEXT|puts] [TEXT|1]

"pu[null 1]ts" 10 20

	[STMT]
	     [DQUOTE] [TEXT|10] [TEXT|20]
		    [TEXT|pu] [BRACKET] [JOIN] [TEXT|ts] [JOIN]
			         [STMT]
					    [TEXT|null] [TEXT|1]
*/
func (interp *Interp) eval_stmt_nodes(container_node *Cnode_t) (Value_t, error) {
	var (
		p          process_t
		v          Value_t
		stmt_node  *Cnode_t
		upper_node *Cnode_t
		inner_node *Cnode_t
		is_stmt    bool
		err        error
		org_vsp    int
	)

	v = new(string) // TODO: change new(string) to a const

	p.interp = interp
	upper_node = container_node
	stmt_node = upper_node.child // the first statement

	org_vsp = p.vsp
	fmt.Printf("START p.sp = %d\n", p.vsp)

	if stmt_node == nil {
		goto done
	}

	for {
	start_over_0:
		if stmt_node.code != CNODE_STMT {
			panic("internal error - not statement node")
		}

		p.push_context(stmt_node, upper_node)
		p.push_string_value("") // placeholder for return value

		inner_node = stmt_node.child
	resume:
		for inner_node != nil {
			//fmt.Printf("handling %d\n", inner_node.code)
			switch inner_node.code {
			case CNODE_BRACKET:
				if inner_node.child != nil {
					upper_node = inner_node
					stmt_node = upper_node.child
					if debug {
						fmt.Printf("going to start over\n")
						interp.dump_cnodes(stmt_node, true)
						fmt.Printf("\n--\n")
					}
					goto start_over_0

				} else {
					// no statements inside []. treat it like an empty string
					p.push_string_value("")
				}

			case CNODE_DQUOTE:
				if inner_node.child != nil {
					p.push_context(stmt_node, inner_node)
					//p.push_string_value("") // no placeholder for return value is needed
					inner_node = inner_node.child
					if debug {
						fmt.Printf("going to start over\n")
						interp.dump_cnodes(stmt_node, true)
						fmt.Printf("\n--\n")
					}
					goto resume
				} else {
					// no statements inside []. treat it like an empty string
					p.push_string_value("")
				}

			case CNODE_BRACE:
				p.push_cnode_value(inner_node)

			case CNODE_TEXT:

				//fmt.Printf("XXXXXXXXXXXXXXXXXXXx[%s]\n", string(inner_node.token))
				err = p.push_string_value(string(inner_node.token))
				if err != nil {
					goto oops
				}

				// TODO: many more types...
			case CNODE_JOIN:
				p.merge_top_values()

			case CNODE_INIT:
				panic("internal error - INIT node must not appear inside a statement")
			}

			inner_node = inner_node.next
		}

		if debug {
			interp.dump_vstack(&p)
		}
		//fmt.Printf("p.ctx.parent_node.code %d p.ctx.container_node.code %d CNODE_STMT %d CNODE_DQUOTE %d CNODE_BRACKET %d\n", p.ctx.parent_node.code, p.ctx.container_node.code, CNODE_STMT, CNODE_DQUOTE, CNODE_BRACKET)
		if p.ctx.container_node.code == CNODE_INIT || p.ctx.container_node.code == CNODE_BRACKET || p.ctx.container_node.code == CNODE_BRACE {
			err = p.call()
			if err != nil {
				goto oops
			}

			is_stmt = true
		} else {
			is_stmt = false
		}

		stmt_node, upper_node = p.pop_context(is_stmt)
		if upper_node != container_node {
			if debug {
				fmt.Printf("resuming... %d upper_node.next %p\n", p.vsp, upper_node.next)
			}

			if upper_node.code != CNODE_BRACKET {
				inner_node = upper_node.next // as if it hit the bottom of the innner for loop
				p.ctx.count++                // use return value  on the stack as an argument
				goto resume
			}
		}

		//fmt.Printf("POPPING VALUE...\n")
		/*v = (*string)(p.pop_value()) // get the return value of the statement.
		if debug {
			interp.dump_vstack(&p)
		}*/
		stmt_node = stmt_node.next

		if stmt_node == nil {
			// go doesn't allow jumping into a block.
			// let's the put the code here
			if upper_node != container_node {
				// the upper node is not the top containing node passed to this function.
				// the contenxt stack must not be empty in this case.
				if upper_node.code != CNODE_BRACKET {
					panic("internal error - invalid cnode type in the context statck")
				}

				inner_node = upper_node.next
				//fmt.Printf(">>>>>>>>>>>>>>>>>> vsp %d ctx.count %d\n", p.vsp, p.ctx.count)

				p.ctx.count++ // use the result value as an argument
				goto resume
			}

			v = p.pop_value() // get the return value of the statement.
			if debug {
				interp.dump_vstack(&p)
			}
			break
		}

		v = p.pop_value() // get the return value of the statement.
		if debug {
			interp.dump_vstack(&p)
		}
	}

done:

	if debug {
		interp.dump_vstack(&p)
		fmt.Printf("END p.sp = %d\n", p.vsp)
	}
	if p.vsp != org_vsp {
		panic("internal error - stack not clean")
	}
	return v, nil

oops:
	return nil, err
}

func (interp *Interp) eval_arg(p *process_t, pos int) (Value_t, error) {
	/*
		var (
			ptr uintptr
		)

		ptr = uintptr(p.GetArg(pos))
		if ptr&1 == 1 { // cnode
			ptr &= ^uintptr(1)
			//interp.dump_cnodes((*Cnode_t)(unsafe.Pointer(ptr)), true)
			//return interp.eval_atom_node((*Cnode_t)(unsafe.Pointer(ptr)).child)
			return interp.eval_stmt_nodes((*Cnode_t)(unsafe.Pointer(ptr)))
		} else {
			return (*string)(unsafe.Pointer(ptr)), nil
		}
	*/

	switch t := p.GetArg(pos).(type) {
	case *string:
		return t, nil
	case *Cnode_t:
		return interp.eval_stmt_nodes(t)
	default:
		panic("internal error - argument type unrecognized")
	}
}

func (interp *Interp) eval_arg_literally(p *process_t, pos int) (Value_t, error) {
	/*
		var (
			ptr uintptr
			//cnode *Cnode_t
		)

		ptr = uintptr(p.GetArg(pos))
		if ptr&1 == 1 { // cnode
			ptr &= ^uintptr(1)
			//cnode = (*Cnode_t)(unsafe.Pointer(ptr))
			//cnode.child i hate this portion....
			return nil, fmt.Errorf("not supported - unable to evaluate {} literally")
		} else {
			return (*string)(unsafe.Pointer(ptr)), nil
		}*/

	switch t := p.GetArg(pos).(type) {
	case *string:
		return t, nil
	case *Cnode_t:
		// TODO: can support this? by storing the original text?
		return nil, fmt.Errorf("not supported - unable to evaluate {} literally")
	default:
		panic("internal error - argument type unrecognized")
	}
}

func (interp *Interp) EvalText(text []rune) (Value_t, error) {
	var (
		v    Value_t
		node *Cnode_t
		err  error
	)

	interp.BeginFeed() // this resets the feed stack to the initial state

	err = interp.FeedRunes(text)
	if err != nil {
		goto oops
	}

	node, err = interp.EndFeed()
	if err != nil {
		goto oops
	}

	//fmt.Printf("--------------------\n")
	//interp.dump_cnodes(node, true)
	//fmt.Printf("--------------------\n")

	v, err = interp.Execute(node)
	if err != nil {
		goto oops
	}

	return v, nil

oops:
	return nil, err
}