// The MIT License (MIT)
//
// Copyright (C) 2026 Scott Duensing
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to
// deal in the Software without restriction, including without limitation the
// rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
// sell copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
// IN THE SOFTWARE.

// symtab.c -- DVX BASIC symbol table implementation

#include "symtab.h"
#include "thirdparty/stb_ds_wrap.h"

#include <ctype.h>
#include <stdlib.h>
#include <string.h>

// Distance from a lowercase ASCII letter to its uppercase counterpart
// ('a' - 'A').  Used by basAsciiUpper to fold case without touching
// bytes outside a-z.
#define BAS_ASCII_CASE_OFFSET 32


// Function prototypes (alphabetical)
BasSymbolT *basSymTabAdd(BasSymTabT *tab, const char *name, BasSymKindE kind, uint8_t dataType);
int32_t basSymTabAllocGlobalSlot(BasSymTabT *tab);
int32_t basSymTabAllocSlot(BasSymTabT *tab);
void basSymTabEnterFormScope(BasSymTabT *tab, const char *formName);
void basSymTabEnterLocal(BasSymTabT *tab);
BasSymbolT *basSymTabFind(BasSymTabT *tab, const char *name);
BasSymbolT *basSymTabFindGlobal(BasSymTabT *tab, const char *name);
void basSymTabFree(BasSymTabT *tab);
void basSymTabInit(BasSymTabT *tab);
int32_t basSymTabLeaveFormScope(BasSymTabT *tab);
void basSymTabLeaveLocal(BasSymTabT *tab);
static char basAsciiUpper(char c);
static void basSymbolFree(BasSymbolT *sym);
static bool namesEqual(const char *a, const char *b);
static uint32_t nameHashCI(const char *name);

BasSymbolT *basSymTabAdd(BasSymTabT *tab, const char *name, BasSymKindE kind, uint8_t dataType) {
    // Determine scope: local > form > global.
    // Only variables get SCOPE_FORM; SUBs/FUNCTIONs/CONSTs remain global.
    BasScopeE scope;

    if (tab->inLocalScope) {
        scope = SCOPE_LOCAL;
    } else if (tab->inFormScope && kind == SYM_VARIABLE) {
        scope = SCOPE_FORM;
    } else {
        scope = SCOPE_GLOBAL;
    }

    uint32_t h = nameHashCI(name);

    // Check for duplicate in current scope (skip ended form symbols)
    for (int32_t i = 0; i < tab->count; i++) {
        if (tab->symbols[i]->formScopeEnded) {
            continue;
        }

        if (tab->symbols[i]->nameHash == h && tab->symbols[i]->scope == scope && namesEqual(tab->symbols[i]->name, name)) {
            return NULL;  // duplicate
        }
    }

    BasSymbolT *sym = (BasSymbolT *)calloc(1, sizeof(BasSymbolT));

    if (!sym) {
        return NULL;
    }

    strncpy(sym->name, name, BAS_MAX_SYMBOL_NAME - 1);
    sym->name[BAS_MAX_SYMBOL_NAME - 1] = '\0';
    sym->nameHash  = h;
    sym->kind      = kind;
    sym->scope     = scope;
    sym->dataType  = dataType;
    sym->isDefined = true;

    // Record owning form for both SCOPE_FORM vars AND SUBs/FUNCTIONs
    // declared inside BEGINFORM...ENDFORM.  SUBs stay at SCOPE_GLOBAL
    // (callable from anywhere) but carry the owning form so the VM can
    // bind form-scope vars correctly when the SUB is dispatched as an
    // event handler for a different form's control.
    if (tab->inFormScope && tab->formScopeName[0] &&
        (scope == SCOPE_FORM || kind == SYM_SUB || kind == SYM_FUNCTION)) {
        strncpy(sym->formName, tab->formScopeName, BAS_MAX_SYMBOL_NAME - 1);
        sym->formName[BAS_MAX_SYMBOL_NAME - 1] = '\0';
    }

    arrput(tab->symbols, sym);
    tab->count = (int32_t)arrlen(tab->symbols);
    return sym;
}


int32_t basSymTabAllocGlobalSlot(BasSymTabT *tab) {
    return tab->nextGlobalIdx++;
}


int32_t basSymTabAllocSlot(BasSymTabT *tab) {
    if (tab->inLocalScope) {
        return tab->nextLocalIdx++;
    }

    if (tab->inFormScope) {
        return tab->nextFormVarIdx++;
    }

    return tab->nextGlobalIdx++;
}


void basSymTabEnterFormScope(BasSymTabT *tab, const char *formName) {
    tab->inFormScope = true;
    strncpy(tab->formScopeName, formName, BAS_MAX_SYMBOL_NAME - 1);
    tab->formScopeName[BAS_MAX_SYMBOL_NAME - 1] = '\0';
    tab->nextFormVarIdx   = 0;
    tab->formScopeSymStart = tab->count;
}


void basSymTabEnterLocal(BasSymTabT *tab) {
    tab->inLocalScope = true;
    tab->nextLocalIdx = 0;
}


BasSymbolT *basSymTabFind(BasSymTabT *tab, const char *name) {
    uint32_t h = nameHashCI(name);

    // Search local scope first
    if (tab->inLocalScope) {
        for (int32_t i = tab->count - 1; i >= 0; i--) {
            BasSymbolT *s = tab->symbols[i];
            if (s->nameHash == h && s->scope == SCOPE_LOCAL && namesEqual(s->name, name)) {
                return s;
            }
        }
    }

    // Search form scope and global scope
    for (int32_t i = tab->count - 1; i >= 0; i--) {
        BasSymbolT *s = tab->symbols[i];
        if (s->formScopeEnded) {
            continue;
        }

        if (s->nameHash == h && (s->scope == SCOPE_FORM || s->scope == SCOPE_GLOBAL) &&
            namesEqual(s->name, name)) {
            return s;
        }
    }

    return NULL;
}


BasSymbolT *basSymTabFindGlobal(BasSymTabT *tab, const char *name) {
    uint32_t h = nameHashCI(name);

    for (int32_t i = 0; i < tab->count; i++) {
        BasSymbolT *s = tab->symbols[i];
        if (s->formScopeEnded) {
            continue;
        }

        if (s->nameHash == h && s->scope == SCOPE_GLOBAL && namesEqual(s->name, name)) {
            return s;
        }
    }

    return NULL;
}


void basSymTabFree(BasSymTabT *tab) {
    // Free every remaining symbol's dynamic arrays and the struct, then
    // release the symbol-pointer array itself.
    for (int32_t i = 0; i < tab->count; i++) {
        basSymbolFree(tab->symbols[i]);
    }

    arrfree(tab->symbols);
    tab->symbols = NULL;
    tab->count   = 0;
}


void basSymTabInit(BasSymTabT *tab) {
    memset(tab, 0, sizeof(*tab));
}


int32_t basSymTabLeaveFormScope(BasSymTabT *tab) {
    int32_t varCount = tab->nextFormVarIdx;

    // Mark all form-scope symbols added since BEGINFORM as ended
    for (int32_t i = tab->formScopeSymStart; i < tab->count; i++) {
        if (tab->symbols[i]->scope == SCOPE_FORM) {
            tab->symbols[i]->formScopeEnded = true;
        }
    }

    tab->inFormScope       = false;
    tab->formScopeName[0]  = '\0';
    tab->nextFormVarIdx    = 0;
    tab->formScopeSymStart = 0;

    return varCount;
}


void basSymTabLeaveLocal(BasSymTabT *tab) {
    // Remove all local symbols, freeing their dynamic arrays and the
    // symbol struct itself.
    int32_t newCount = 0;

    for (int32_t i = 0; i < tab->count; i++) {
        if (tab->symbols[i]->scope == SCOPE_LOCAL) {
            basSymbolFree(tab->symbols[i]);
        } else {
            if (i != newCount) {
                tab->symbols[newCount] = tab->symbols[i];
            }

            newCount++;
        }
    }

    arrsetlen(tab->symbols, newCount);
    tab->count        = newCount;
    tab->inLocalScope = false;
    tab->nextLocalIdx = 0;
}


// ============================================================
// Fold a single ASCII byte to upper case.  Char in, char out (not int
// via toupper) so bytes >= 0x80 pass through unchanged and the uint8_t
// then uint32_t cast in nameHashCI stays well defined.
// ============================================================
static char basAsciiUpper(char c) {
    if (c >= 'a' && c <= 'z') {
        c -= BAS_ASCII_CASE_OFFSET;
    }

    return c;
}


// ============================================================
// Free a single symbol: its dynamic arrays and the struct itself.
// ============================================================
static void basSymbolFree(BasSymbolT *sym) {
    arrfree(sym->patchAddrs);
    arrfree(sym->fields);
    free(sym);
}


// ============================================================
// Case-insensitive FNV-1a hash used to accelerate symbol-table lookups.
// Caller computes hash of search-name once; each entry stores its own
// precomputed hash, so per-entry comparison is a fast uint32 compare
// that nearly always rejects non-matches without calling namesEqual.
// ============================================================
static uint32_t nameHashCI(const char *name) {
    uint32_t h = 0x811C9DC5u;

    while (*name) {
        char c = basAsciiUpper(*name);
        h ^= (uint32_t)(uint8_t)c;
        h *= 0x01000193u;
        name++;
    }

    return h;
}


// ============================================================
// Case-insensitive name comparison
// ============================================================
static bool namesEqual(const char *a, const char *b) {
    while (*a && *b) {
        char ca = basAsciiUpper(*a);
        char cb = basAsciiUpper(*b);

        if (ca != cb) {
            return false;
        }

        a++;
        b++;
    }

    return *a == *b;
}