use crate::compiler::{CompileCtx, Compiler, Label};
use oxide_bytecode::opcode::{self, OpCode};
use oxide_parser::Statement;

impl Compiler {
    fn count_switch_statement(&self, stmt: &oxide_parser::SwitchStatement<'_>, ctx: &mut CompileCtx) {
        let id = ctx.next_label_id();
        let end_label = Label::SwitchEnd(id);
        ctx.push_switch(end_label);
        self.count_expression(&stmt.discriminant, ctx);
        let compare_reg_checkpoint = ctx.reg_checkpoint();
        let cases = &stmt.cases;
        for case in cases.iter() {
            if let Some(test) = &case.test {
                self.count_expression(test, ctx);
                ctx.projected_pc += 1;
                ctx.alloc_reg();
                ctx.projected_pc += 1;
                ctx.restore_reg_checkpoint(compare_reg_checkpoint);
            }
        }
        let has_default = cases.iter().any(|c| c.test.is_none());
        if !has_default {
            ctx.projected_pc += 1;
        }
        for (case_idx, case) in cases.iter().enumerate() {
            let case_label = Label::SwitchCase(id, case_idx as u32);
            ctx.labels.label_map.insert(case_label, ctx.projected_pc);
            for s in &case.consequent {
                self.count_statement(s, ctx);
            }
        }
        ctx.labels.label_map.insert(end_label, ctx.projected_pc);
        ctx.pop_switch();
    }

    fn emit_switch_statement(&self, stmt: &Statement, ctx: &mut CompileCtx) -> Result<Option<u8>, String> {
        let Statement::SwitchStatement(sw) = stmt else {
            return Ok(None);
        };
        let id = ctx.next_label_id();
        let end_label = Label::SwitchEnd(id);
        ctx.push_switch(end_label);
        let disc_reg = self.emit_expression(&sw.discriminant, ctx)?;
        let compare_reg_checkpoint = ctx.reg_checkpoint();
        let cases = &sw.cases;
        for (case_idx, case) in cases.iter().enumerate() {
            if let Some(test) = &case.test {
                let test_reg = self.emit_expression(test, ctx)?;
                let eq_reg = ctx.alloc_reg();
                ctx.emit(opcode::encode(OpCode::EQ, eq_reg, disc_reg, test_reg));
                let case_label = Label::SwitchCase(id, case_idx as u32);
                ctx.emit_jmp_if_true_labeled(eq_reg, case_label);
                ctx.restore_reg_checkpoint(compare_reg_checkpoint);
            }
        }
        let has_default = cases.iter().any(|c| c.test.is_none());
        if !has_default {
            ctx.emit_jmp_labeled(end_label);
        }
        for (case_idx, case) in cases.iter().enumerate() {
            let case_label = Label::SwitchCase(id, case_idx as u32);
            ctx.labels.label_map.insert(case_label, ctx.bytecode.len());
            for s in &case.consequent {
                self.emit_statement(s, ctx)?;
            }
        }
        ctx.labels.label_map.insert(end_label, ctx.bytecode.len());
        ctx.pop_switch();
        Ok(None)
    }

    pub(crate) fn count_switch_domain(&self, stmt: &Statement, ctx: &mut CompileCtx) {
        if let Statement::SwitchStatement(sw) = stmt {
            self.count_switch_statement(sw, ctx);
        }
    }

    pub(crate) fn emit_switch_domain(&self, stmt: &Statement, ctx: &mut CompileCtx) -> Result<Option<u8>, String> {
        match stmt {
            Statement::SwitchStatement(_) => self.emit_switch_statement(stmt, ctx),
            _ => Ok(None),
        }
    }
}